Contents

This publication is also available online in a web-accessible version at https://pub.norden.org/temanord2022-510.

Abbreviations

PFAS Abbreviations

1. Foreword

Per- and polyfluoroalkyl substances (PFASs) are a large group of substances that have been widely used in articles since many years. They are found wherever extreme conditions prevail and particularly high demands are placed on materials. Their use spans over many different sectors ranging from fire-fighting foams to the manufacture of everyday articles like water-repellent outdoor jackets or stain-proofing agents.

On the other side, PFASs are not easily degradable and can remain in the environment for decades. In addition, the use of PFASs has raised human and environmental concerns. In Europe, some PFASs are therefore classified as persistent, bioaccumulative and toxic (PBT) and very persistent and very bioaccumulative (vPvB) under the REACH Regulation.

The following report provides an overview of currently available analytical methods for PFASs in different matrices. The methods identified can be used e.g. in the enforcement of a potential restriction of PFASs in the relevant matrices. Various sources of information have been investigated including recent peer-review literature and well-established standards.

2. Summary

Based on the electronegativity of Fluorine, the carbon fluorine (C-F) bond is one of the strongest in nature and becomes even stronger when a carbon atom is fully (per-) or partially (poly-) fluorinated. PFAS chemicals are exactly that: perfluorinated or polyfluorinated organic substances. As a result of the strong C-F bonds, PFAS chemicals have unique properties. These properties include a high resistance to external factors like extreme temperatures, pH, oxidation (non-flammable) and abrasion. Furthermore, some PFAS chemicals show high hydrophobicity or oil-repellent properties to the extent that water, water-containing substances, and oil-based compounds cannot stick/wet the material. These unique properties also have some considerable downsides, for example the fact that PFASs do not readily degrade in the environment and are therefore persistent in almost all cases.

PFASs have been used in a variety of industries since the 1940s (e.g. chromium plating, aerospace hydraulic fluids, fire-fighting foams, and textile finishing). A recent publication (Glüge et al., 2020) identified 21 industry branches with more than 200 uses. Looking at these, it would be reasonable to assume that the majority of industries use PFASs in one way or another.

PFASs can be found in the environment and humans across Europe, whereby areas around industrial production, manufacturing and application sites have been found to be particularly contaminated. This has led to contaminated drinking water around PFASs manufacturing factories in Belgium, Italy and the Netherlands, and around airports and military bases with fire-fighting training sites in Germany, Sweden, Denmark, Norway and the United Kingdom.

Against this background policy makers of different European countries joined forces and work towards a broad restriction for PFAS substances. Appropriate analytical methods need to be available for the enforcement and monitorability of a restriction. The present report summarised available analytical methods for several specific uses and draw conclusions for monitoring compliance measurements. The following table provides the most relevant information.

Note: ^{[1]Determination of extractable perfluorooctanesulfonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS; German version CEN/TS 15968:2010 https://www.beuth.de/en/pre-standard/din-cen-ts-15968/119731674 [2]DS/CEN/TS 15968:2010, "Determination of extractable perfluorooctanesulphonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS"}​

Overall, it can be concluded that:

• For some matrices there are well-established standards available (or standards that are used although not specifically designed for that matrix) that exclusively focus on a targeted sub-set of PFASs (mostly 10-30 individual PFASs). There are standards available for example by the International Organization for Standardization (ISO), by the US EPA, the European Committee for Standardization, or the German institute for Standardization (DIN).
• A large number of scientific publications is available covering method development and method improvement studies. Especially with the increasing awareness for PFAS substances in the recent years, the number of publications increased and is still increasing.
• The publications in the scientific literature spans from purely experimental topics to the use of standard methods for e.g. new matrices. It needs to be taken into account that some methods described are still in a stage that only very specialised laboratories can apply them, while others are validated and can be used in a common laboratory.    
• There are no standards available for total fluorine methods or the Total Organic Precursors assay (TOPA). Commercial laboratories, however, offer these measurements (often in combination with targeted approaches).
• US EPA is currently developing a standard operating procedure tool for determination of Total Organic Fluorine (TOF) in environmental samples. Additionally, the need for a standard procedure for TOPA measurements of PFAS precursors in environmental matrices is considered by EPA.^{[1]https://www.epa.gov/water-research/pfas-analytical-methods-development-and-sampling-research}
• In the EU, a first interlaboratory comparison of Extractable Organic Fluorine (EOF) and fluorine mass balance in sludge and water matrices demonstrated promising accuracy, robustness and reporting limits but poor extraction efficiency was observed for some targets (e.g. trifluoroacetic acid) (Kärrman et al., 2021).
• When results of targeted analysis are compared to measurements of total fluorine (TOF, EOF, AOF) or PFAS-precursor analysis (TOPA) it is evident that the targeted methods “miss the whole picture”, meaning that a lot of PFASs are overlooked.
• Often, individual PFAS substances contribute only to a small fraction of the total fluorine in a sample, and therefore guidance values that have been derived for single substances may be of limited value in assessment of exposure and risk.
• For the matrix “food contact materials” there is a limit value based on the total fluorine concentration: The Danish Food and Veterinary Administration suggested an indicator value of 10 μg/dm² Organic Fluorine (OF) for food packaging, where fluorine concentration in paper below this value can be assumed to not be treated with PFASs.

For firefighting foams, an NGO (Clean Production Action) defines “PFAS-free” as zero intentionally added PFASs to the product and PFASs contamination (measured as TOF) in the product must be less than 0.0001 percent by weight of the product (1 ppm)^{[2]https://www.greenscreenchemicals.org/certified/fff-standard}. 

3. Introduction

Based on the electronegativity of Fluorine, the carbon fluorine (C-F) bond is one of the strongest in nature and becomes even stronger when a carbon atom is fully (per-) or partially (poly-) fluorinated. PFAS chemicals are exactly that: perfluorinated or polyfluorinated organic substances. As a result of the strong C-F bonds, PFAS chemicals have unique properties. These properties include a high resistance to external factors like extreme temperatures, pH, oxidation (non-flammable) and abrasion. Furthermore, some PFAS chemicals show high hydrophobicity or oil-repellent properties to the extent that water, water-containing substances, and oil-based compounds cannot stick/wet the material. These unique properties also have some considerable downsides, for example the fact that PFASs do not readily degrade in the environment and are therefore persistent in almost all cases.

Naturally occurring fluorinated organic compounds are rare and most PFASs are anthropogenic. Based on a list published in 2018 by the OECD/UNEP, it is known that around 5000 PFAS substances are marketed globally (meaning that in 2017 about 4,730 individual substances had a designated CAS number) (OECD, 2018). Based on structure filters to the entire US EPA DSSTox database (currently exceeding 900,000 substances), the US EPA concluded that there might be more than 9,200 PFAS substances (USEPA, 2020).

PFASs have been used in a variety of industries since the 1940s (e.g. chromium plating, aerospace hydraulic fluids, fire-fighting foams, and textile finishing). A recent publication (Glüge et al., 2020) identified 21 industry branches with more than 200 uses. Looking at these, it would be reasonable to assume that the majority of industries use PFASs in one way or another.

PFASs can be found in the environment and humans across Europe, whereby areas around industrial production, manufacturing and application sites have been found to be particularly contaminated. This has led to contaminated drinking water around PFASs manufacturing factories in Belgium, Italy and the Netherlands, and around airports and military bases with fire-fighting training sites in Germany, Sweden, Denmark, Norway and the United Kingdom. The total number of sites potentially emitting PFASs is estimated to be in the order of 100,000 in Europe^{[1]https://www.eugreenweek.eu/virtual-conference/farewell-pfas-calling-time-forever-chemicals}.

The above provides on a first insight into the complexity of the PFAS chemistry as regards the number of substances and the large number of matrices, which can contain PFASs (e.g., environmental, biological, food and consumer goods). A broad range of analytical techniques have been developed and implemented for the analysis of PFASs. During the last years significant progress has been made in developing and implementing techniques for the analysis of PFASs.

The techniques used can be separated in three broad groups:

1. Target analysis
2. Total fluorine (organic fluorine) methods
3. Non-target analysis, suspect screening and total oxidizable precursor assay (TOPA)

Details of each of the different analytical approaches are provided in chapter 3.3.

3.1 PFASs Chemistry and Terminology

Chemically, PFAS molecular structures consist of a linear or branched aliphatic alkyl chain (or chains) in which either all or part of the hydrogens are replaced by fluorine, so that they contain partially (i.e. poly) or fully (i.e. per) fluorinated alkyl chains.

In 2011, (Buck et al., 2011) suggested  a common terminology, classification and acronyms for PFAS substances and substance groups. Over the years, this terminology has been revised and adapted several times in order to include also more diverse and overlooked PFASs. In July 2021, the OECD published a report “Reconciling Terminology of the Universe of Per- and Polyfluoroalkyl Substances” that provides recommendations and practical guidance to all stakeholders about the terminology of PFASs (OECD, 2021). Alongside the report a recording of a webinar^{[1] https://www.oecd.org/chemicalsafety/portal-perfluorinated-chemicals/webinars/#d.en.418532} is available. In this report a revised PFAS definition is highlighted that PFASs describe as:

“PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF₃) or a perfluorinated methylene group (–CF₂–) is a PFAS.”

Based on this relatively broad definition the PFAS universe is a highly complex chemical class with compounds with diverse functional groups attached to the fluoroalkyl moiety/-ies.

Within this universe PFASs can be grouped:

• Perfluoroalkyl acids (PFAAs)
• Polyfluoroalkyl acids (PolyFAAs)
• PFAA precursors
• Other PFASs

PFASs can be divided further into two sub-groups: non-polymeric and polymeric PFASs. Within the polymeric PFAS group differentiation is made between fluoropolymers (polymers consisting of a fluorinated polymer (carbon-only backbone), perfluoropolyethers (with ether linkages in the backbone), and side-chain fluorinated polymers (polymers consisting of non-fluorinated polymer backbones with per- or polyfluoroalkyl side-chains attached). Figure 1 shows a comprehensive overview of PFAS groups, their structural traits, examples and notes on whether corresponding common nomenclatures (including acronyms) exist as taken from (OECD, 2021).

Perfluoroalkyl acids (abbreviated PFAAs) consist of a perfluoroalkyl chain attached to a charged functional moiety (primarily carboxylate (PFCA), sulfonate (PFSA), or phosphonate (PFPA)). The two most widely known PFAAs have an eight-carbon chain and are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). The fluoroalkyl chain itself can contain an oxygen atom, i.e. an ether group, then creating so called perfluoroalkylether carboxylic/sulfonic acids (PFECAs/PFESAs). Representatives of this group, like ADONA or GenX, are known substitutes of previously widely used PFASs. No polymeric PFASs can be found in this group. It should be noted that PFAAs are different from another class of perfluorocarbons, the perfluoroalkanes, which are primarily used clinically for oxygenation and respiratory ventilation.

Polyfluoroalkyl acids (PolyFAAs) are, in comparison to PFAAs, not perfluorinated meaning that at least one of the carbon atoms in the alkyl chain of the substance carries a hydrogen atom (or chlorine, bromine or iodine). Also, in this group no polymeric PFASs are present.

PFAA precursors refer to chemicals that can transform and form PFAAs in the environment and biota. In this particular group polymeric side chain fluorinated polymers are included as well as fluorotelomer compounds and substances that are based on perfluoroalkane sulfonyl fluoride (PASF-based). The latter includes for example N-methylperfluorooctane sulfonamidoacetic acid (FOSAA), that is a known precursor to PFOS.

In the group “Other PFAS” many commonly known fluoropolymers are included (like for example (Polytetrafluoroethylene, PTFE).

Figure 1: A comprehensive overview of PFAS groups, their structural traits, examples and notes on whether corresponding common nomenclatures (including acronyms) exist as taken from (OECD, 2021).

3.2 Regulation of PFASs

Various individual PFASs have been regulated in global or European regulations (such as the POPs or REACH Regulations) since the early 2000s. In terms of substances, these regulations first targeted the long-chain (C8) PFASs, such as PFOS and PFOA. As a result of the regulatory pressure and voluntary phase-outs, many manufacturers and users switched to short-chain (C6) alternatives. This step is nowadays considered a "regrettable substitution", as the short-chain PFASs also have properties of concern. As a result, these substances have been or will be the target of further regulatory measures (SVHC identification, restrictions etc.).

The European Commission published the “Chemicals Strategy for Sustainability” on the 14^th of October 2020. The strategy plays an important role in the framework of the EU’s zero pollution ambition, which is a key component of the European Green Deal. Although the chemicals strategy agrees that many chemicals are essential for the well-being, high living standards and comfort of modern society, it also points out that many chemicals have hazardous properties that can harm the environment and human health. Within this strategy, PFASs are specifically addressed as one of the action points. The commission aims at “phasing out the use of per- and polyfluoroalkyl substances (PFASs) in the EU, unless their use is essential”.

As a key step towards this goal, also in 2020, ECHA announced that a restriction for the whole group of PFASs is planned. The proposal will be submitted by the competent authorities for REACH of the Netherlands, Germany, Denmark, Sweden, and Norway in 2022. Such a restriction may cover the production, import, placement on the market and/or use of PFASs and set specific conditions for different applications. Further regulatory actions on PFASs beyond REACH include sector-specific legislations. These actions are discussed in detail in the staff working document^{[1]https://ec.europa.eu/environmenttemanord2022-510.pdfchemicals/2020/10/SWD_PFAS.pdf and https://www.ubc-sustainable.net/sites/www.ubc-environment.net/files/media/2._bertato_ec_dg_env.pdf} on PFASs and in related presentations^{[2]https://eurion-cluster.eu/wp-content/uploads/2021/02/1-Christina-de-Avila_Commission_presentation.pdf}. The actions, for example, address PFASs with a group approach, under relevant legislation on water, sustainable products, food, industrial emissions, and waste. The impacts on other legislation of the PFASs strategy as laid out in the staff working document are graphically shown in Figure 2.

Figure 2: Strengthening legislations - goals and impacts on other legislation of the PFASs strategy. Retrieved from “Initiatives to regulate PFASs at EU level and beyond”.^{[1]https://ec.europa.eu/environmenttemanord2022-510.pdfchemicals/2020/10/SWD_PFAS.pdf and https://www.ubc-sustainable.net/sites/www.ubc-environment.net/files/media/2._bertato_ec_dg_env.pdf}

3.3 PFASs analysis

In the following chapter more details on the different analytical approaches are presented. 

3.3.1 Target analysis

Targeted methods are used to quantify levels of specific PFASs in various matrices. In general, targeted methods involve chromatography hyphenated to mass spectrometry (MS). Liquid (LC) or gas chromatography (GC) can be applied. For quantification an appropriate reference standard is necessary. Standards are only available for certain PFASs and therefore only these specific substances can be quantified. The choice of PFASs has been driven mainly by a mixture of practical analytical reasons and the purpose to act regulatory compliant. Thus, the main focus lays on PFAAs (especially PFCAs and PFSAs) and some newer replacement substances like fluorotelomers and perfluoroalkylethers (ADONA, GenX).

Target analysis of PFASs is well established. For example, there are two US EPA methods for water (drinking and non-potable water) which focus on a specific subset of PFASs^{[1]https://www.epa.gov/water-research/pfas-analytical-methods-development-and-sampling-research}:​ Method 8327^{[2]SW-846 Test Method 8327: Per-and Polyfluoroalkyl Substances (PFAS) by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) https://www.epa.gov/hw-sw846/sw-846-test-method-8327-and-polyfluoroalkyl-substances-pfas-liquid-chromatographytandem SW-846 Test Method 3512: Solvent Dilution of Non-Potable Waters https://www.epa.gov/hw-sw846/sw-846-test-method-3512-solvent-dilution-non-potable-waters} includes 24 PFAS analytes (16 PFAAs and 8 other PFASs, including HFPO-DA (GenX) and ADONA^{[3]GenX and ADONA are processing aids (dispersing agents (surfactants)) in the polymerization of some typesof fluoropolymers – e.g. dispersion polymerization of tetrafluoroethylene (to produce dispersion of finepowder PTFE). Both were considered as PFAS alternatives.}). Method 537.1 tests for 18 PFAS analytes (12 PFAAs and 6 other PFAS, including HFPO-DA (GenX). At national level, the German Institute for Standardisation (DIN) established standard methods DIN 38407-42^{[4]DIN 38407-42 “German standard methods for the examination of water, waste water and sludge - Jointlydeterminable substances (group F) - Part 42: Determination of selected polyfluorinated compounds (PFC) inwater - Method using high performance liquid chromatography and mass spectrometric detection (HPLC/MS-MS) after solid-liquid extraction” https://www.beuth.de/de/norm/din-38407-42/137282966} and DIN 38414-14^{[5]DIN 38414-14 “German standard methods for the examination of water, waste water and sludge - Sludge andsediments (group S) - Part 14: Determination of selected polyfluorinated compounds (PFC) in sludge,compost and soil - Method using high performance liquid chromatography and mass spectrometric detection(HPLC-MS/MS)” https://www.beuth.de/en/standard/din-38414-14/142612398} for quantitative determination of selected perfluorinated compounds by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) following solid phase extraction (SPE), in unfiltered water and in soil samples. The selected substances are according to this standard method mostly PFCAs (C4-C8), PFHxS, and PFOS. The validation document of these method states (in German), that also other PFASs can be measured if they contain an acidic group. Volatile fluorotelomers (like fluorotelomer alcohols) cannot be determined using this method^{[6]https://www.wasserchemische-gesellschaft.de/dev/validierungsdokumente?download=33:f42-din-38407-42-2011-03&lang=de}.

Target analysis is advantageous in that it provides an accurate PFASs concentration, and the achievable 1-2 ng/L (1000 ppt) reporting limit meets the regulatory stan|dards. However, this analytical technique only applies to a limited subset of PFASs (as above explained), and it is not sufficient to provide a comprehensive indication of the total PFASs that may exist in contaminated soils, water or any other sample.

The established methods select the linear structures, although it is well known that branched structures are also present due to different manufacturing approaches. The presence of branched isomers typically indicates electrochemical fluorination (ECF) manufacturing, whereas fluorotelomerization (FT)-based products are predominantly linear (Charbonnet et al., 2021). Many branched PFAS isomers can be separated from their linear counterparts by LC and analysed by targeted methods. Exclusion of branched PFAS isomers from quantification can result in low concentration bias. However, branched isomer standards are not readily available for all PFASs. Their isomer ratios in environmental samples can also help to identify the manufacturing source of the compound. Research is still ongoing, but there are already reviews available that give an overview for distribution of branched PFASs in different environmental matrices (Schulz et al., 2020)^{[7]https://cdnmedia.eurofins.com/european-east/media/2184182/branched_pfas_short_facts_1804.pdf}. A technical advisory document describing laboratory analysis of drinking water samples for perfluorooctanoic acid (PFOA) using EPA Method 537 Rev. 1.1 specifies the handling of PFOA and branched PFOA^{[8]https://www.epa.gov/sites/default/files/2016-09/documents/pfoa-technical-advisory.pdf}. Recently new developments in improving separation, verification and identification of PFASs have been done by implementing ion mobility as an additional separation step. This methodology is still in research phase but can lead in the future to improved PFASs detection as well as improved branched PFASs separation (Yukioka et al., 2020).

3.3.2. Total fluorine (organic fluorine) methods

Total fluorine (TF) is the sum of Inorganic Fluorine (IF) and Organic Fluorine (OF) or Total Organic Fluorine (TOF), respectively. TOF as a sum parameter includes fluorine content of all PFASs and their precursors in the sample.

Organofluorine analysis entails the analysis of the Extractable Organic Fluorine (EOF) fraction which can be further divided into quantifiable and unquantifiable OF (Figure 3). Extraction can be performed using the same solvent systems used for conventional targeted methods. EOF is useful in the evaluation of PFASs content, but due to the large range of variability between the chemical composition of PFASs, the extraction method used needs to be chosen with care and one method will not be suitable for all classes of PFASs. Therefore, Non-Extractable Organic Fluorine (NEOF) content must be considered (Koch, 2020). In the EU, a first interlaboratory comparisons of EOF and fluorine mass balance in sludge and water matrices demonstrated promising accuracy, robustness and reporting limits but poor extraction efficiency was observed for some specific substances (e.g. trifluoroacetic acid) (Kärrman et al., 2021).  

Also, Adsorbable Organic Fluorine (AOF) can be measured. Therefore, the sample (e.g. water) is passed through an adsorbent (e.g. a mixed-mode weak anion exchange solid-phase extraction (SPE) cartridge) thereby adsorbing the PFASs.^{[1]https://cdnmedia.eurofins.com/apac/media/601777/environote-1080-tof.pdf}  

Figure 3: Mass balance analysis of fluorine. Illustration taken from (Koch, 2020).

There are several methods for quantitative determination of TF, TOF, EOF or AOF available. The most discussed methods are combustion ion chromatography (CIC), particle-induced gamma-ray emission spectroscopy (PIGE), instrumental neutron activation analysis (INAA), and X-ray photoelectron spectroscopy (XPS). PIGE and XPS are surface measurement techniques, whereas INAA and CIC are bulk volume techniques. PIGE, INAA and XPS are non-destructive high throughput methods. In one comparative study of TF by INAA, PIGE and CIC, the authors stated that CIC displayed the lowest detection limits (Schultes et al., 2019). Assuming a 10 mg sample size, detection limits were 0.8 ppm for CIC, followed by INAA (20 ppm) and PIGE (38 ppm). The methods are introduced in more detail in the following sections. In theory, all these methods can be used for determination of TF/TOF, but only XPS is selective between TOF and IF. Therefore, IF has to be removed from the sample for determination of TOF. However, for many consumer products it can be assumed that contribution from IF is negligible. For AOF or EOF determination sample pre-treatment is necessary, and the respective extracts can be analysed.

Combustion ion chromatography (CIC)

The CIC method can be used for direct measurement of TF. Also, the quantitative amount of EOF after sample extraction can be estimated by CIC or the amount of AOF after elution of the adsorbent. The principle of the CIC is that a sample (solid, liquid or gaseous) is thermally oxidized in a moisturized oxygen stream at a high temperature (900-1050 °C) so that OF is converted into hydrogen fluoride (HF). HF is then absorbed in aqueous media (e.g. MilliQ water or hydroxide peroxide) and free anions (e.g. F^-) are determined by ion chromatography followed by conductimetric detection. Several interferences need to be considered, in particular the content of inorganic fluoride and chloride as well as the devitrification of the combustion tube (quartz) caused by high levels of alkaline earth elements (e.g. potassium, calcium). Limit of detections (LODs) of 1-100 ng F/L in water samples have been reported, after 500-800 times sample concentration (Kärrman et al., 2019; Miyake et al., 2007; Wagner et al., 2013a). In determination of EOF with CIC, differences between calibration with IF and OF have to be considered, as well as dissimilar combustion efficiencies for various PFASs (Aro, Eriksson, et al., 2021). Both can lead to underestimating EOF content. At least one commercial laboratory has invested in automated CIC systems for analysis of TF, AOF and EOF. Direct combustion of the materials results in reporting limits of 0.05 mg F/kg (TF) which can be lowered with a prior extraction step to 0.02 mg F/kg (EOF). For AOF, reporting limits are depending on the presence of suspended solids (0.001 mg F/L for clean water compared to 0.01 mg F/L with significant amounts of suspended solids).^{[1]https://cdnmedia.eurofins.com/apac/media/601777/environote-1080-tof.pdf} 

Particle-induced gamma-ray emission spectroscopy (PIGE)

PIGE a long-known ion beam technique was recently adapted for the quantitative determination of TF in textiles and paper (Ritter et al., 2017). Here, an accelerated proton ion beam will excite the atoms in the sample, resulting in the distinct fluorine gamma ray emittance, whose intensity is proportional to the amount of fluorine in the sample. PIGE measures surface material up to a depth of 250 µm, thus is commonly used for solid samples, although powders can be compressed into pellets and liquid samples could also be analysed using a solid support (e.g. sorbent) (Koch, 2020). The method has the advantages of being non-destructive, no matrix effects are overserved, no sample pre-treatment is needed and therefore having high throughput (>20 samples per hour). With this method acceptable sensitivity (ppm levels) can be achieved. As PIGE is non-selective between IF and TOF, the removal of IF is needed for TOF estimation of complex matrices such as soil, sediment, and biota. Other drawbacks are the need for a neutron activation source and highly specialized operators to use the instrumentation (Koch, 2020).

Instrumental neutron activation analysis (INAA)

INAA is a non-destructive multi-element analysis for both major and trace elements and can perform both qualitative and quantitative identification for a wide range of sample matrices. In INAA, a sample is bombarded with neutrons leading to radioactive isotopes. The radioactive emission and decay are element specific and can be used to determine the elements. The method was first applied in (Schultes et al., 2019) for quantitative determination of EOF of consumer products. However, interferences from e.g. aluminium were found for the tested certified reference material, making INAA unsuitable for that matrix. In this study the F detection limit was 20 µg/g (= 20 ppm) for a sample with the mass of 0.01 g. INAA has advantages of being a non-selective high throughput method and can measure bulk samples as well as liquid and solid matrices (Koch, 2020).  

X-ray photoelectron spectroscopy (XPS)

XPS is another non-destructive analysis method which was recently adapted for quantitative determination of TOF in consumer products (in % F) (Tokranov et al., 2019). XPS spectra are acquired by irradiating the surface of a material with an X-ray under high vacuum while simultaneously recording the number of electrons emitted and their kinetic energy, which is specific to certain chemical states (e.g. CF₂ at ~292 eV and CF₃ at ~293 eV groups) (Koch et al., 2020). Thus, this technique can confirm the presence of PFASs Also, the method can distinguish between IF and TOF, which gives XPS an advantage compared to PIGE and INAA. XPS is limited to a surface depth of 0.01 mm. XPS instruments are readily available in research laboratories and the method has a good sensitivity (Koch, 2020).

¹⁹F nuclear magnetic resonance spectroscopy (¹⁹F NMR)

¹⁹F NMR has been employed for the quantitative determination of PFASs in some biological matrices. The identification of PFASs is based on the chemical shift of fluorine atoms under NMR. Quantification of total PFASs was estimated for example using the peak area of the terminal CF₃ groups and a calibration curve constructed from the standard of a single compound such as PFOS (Moody et al., 2001). The method is selective for different PFASs, including branched isomers. However, due to the low sensitivity of the ¹⁹F NMR extensive pre-concentration or prolonged acquisition time (45 or 60 min) is required (Koch, 2020). Furthermore, this method is not commonly available due to high costs for equipment and high operation costs.

Other methods

There are more methods for analysis of EOF in environmental samples that are still under development (Koch, 2020) (for more information see chapter 4.18.1): Inductively coupled plasma mass-spectrometry (ICP-MS), continuum source molecular absorption spectrometry (CS-MAS), defluorination with sodium biphenyl (SBP), potentiometric and fluorimetric detection, and reversed phase LC-UV or GC coupled with a flame ionization detector (FID), electron capture detector (ECD) or MS.

3.3.3 Non-target analysis

Non-targeted screening (NTS) is used for a broad screening purpose and allows detection and identification of unexpected or previously unknown PFASs. The method uses chromatography coupled to a high-resolution mass spectrometer (HRMS). Hybrid instruments, such as quadrupole time-of-flight (Q-TOF) and linear ion trap-orbitrap (LTQ-Orbitrap) instruments, have become increasingly common in laboratories. These allow the accurate-mass acquisition (1-2 ppm error) of both full-spectrum and product-ion spectrum. Detection and identification of PFASs using NTS generally involves (i) the acquisition of full-scan spectra, (ii) selection of potentially relevant features, (iii) assigning plausible molecular formulas, (iv) product-ion acquisition and eventually (v) confirmation of the compound by analysing a reference standard (if available) or tentatively propose a structure.^{[1]http://api.kwrwater.nl/uploads/2020/07/Umweltbundesamt-Final-Workshop-Report-(Workshop-and-workshop-report-on-PFAS-monitoring)-van-Keer-Hohenblum-B-en-et-al-Conference-Center-Albert-Borschette-Brussels-13-14-January-2020.pdf} Strategies for the identification of PFASs during NTS can involve various approaches, e.g. mass defect filtering of CF₂. If an unknown compound is tentatively identified, it should be confirmed with an available reference standard. It then can be quantified using similar approaches as in targeted analysis (external calibration or labelled internal standards) and similar detection limits can be reached (Liu et al., 2020).^{[2]https://assets.thermofisher.com/TFS-Assets/CMD/Application-Notes/an-65499-lc-ms-epa-method-537-1-validation-an65499-en.pdf} Since a high number of compounds detected in NTS have no standards available yet, semi-quantification of these compounds can only be performed using resembling reference compounds. Overall, (Liu et al., 2020)NTS helps to identify previously unknown PFASs using a broad screening approach. However, the methods require a high degree of labour and take accordingly long for a result, with a high degree of analytical expertise needed.

During a suspect screening analysis (SSA) the accurate mass, isotope pattern and fragmentation pattern of molecular features obtained from HRMS are compared to databases with known PFASs, such as the USEPA CompTox Chemistry Dashboard and NORMAN Suspect List Exchange (Koch, 2020). SSA are nowadays subject to current research and criteria to identify PFASs are proposed (Yu et al., 2020).

The Total Oxidizable Precursors Assay (TOP assay or TOPA) is a method to identify PFAA precursors. It was originally developed by (Houtz & Sedlak, 2012). The method converts PFAA precursors (e.g. fluorotelomers, such as 6:2 FTSA) into PFAAs with a hydroxyl radical based oxidation reaction. The pre and post concentrations of common target PFASs is evaluated with the same methods as for conventional targeted analysis (e.g., LC-MS/MS). If there are PFAA precursor present, the concentration of the respective PFAA is increasing after the oxidation process. Oxidation conversion yields are PFAS compound dependent (Martin et al., 2019) and there are many other factors that affect the TOPA process. Usually, the oxidation step is performed prior to extraction. Depending on the sample matrix, pH can be affected, or the matrix can react with the hydroxyl radicals, which can slow down the reaction or lead to non-quantitative conversion. Oxidation can be conducted after sample extraction to reduce matrix effects (Houtz et al., 2013), but in this case some PFAA precursors may not be extracted from the sample. Completeness of oxidation can be checked by adding a ¹³C mass labelled precursor. If all the added precursor is consumed, the reaction is deemed to be complete (assuming higher concentrations of the added precursor). Alternatively, TOPA is performed in duplicate with one of the extracts being 10 times diluted. If the measured levels of PFAA between the original and diluted samples are the same, then the oxidation process is presumed to be completed. With total oxidizable precursor assay, also unknown precursors for C2-C3 perfluoroalkyl carboxylic acids can be traced back when looking for legacy and emerging PFASs (Chen et al., 2019; B. Wang et al., 2020). Currently there is no standard method for TOPA available, but TOPA is already offered by some commercial laboratories.^{[3]https://www.eurofins.de/food-analysis/food-news/food-testing-news/pfas-top-assay/} US EPA is developing a standard method for TOPA for environmental samples.^{[4]https://www.epa.gov/pfas/pfas-strategic-roadmap-epas-commitments-action-2021-2024} One drawback of TOPA is that precursors are determined indirectly and therefore their chemical identity is unknown. Also, the method is comparative labour intensive.

3.4 Fluorinated polymer analysis

As already stated earlier in the report, PFASs can be divided into non-polymeric and polymeric PFASs (fluorinated polymers). The fluorinated polymers can be subdivided into side-chain fluorinated polymers, fluoropolymers and perfluoropolyethers. However, not all analytical methods discussed in the previous chapter can be applied to fluorinated polymers. In general, targeted analysis was developed for selected non-polymeric PFASs (especially PFAAs) whereas methods for determination of total (organic) fluorine content can also be applied to samples containing fluoropolymers. TOPA can be performed on cleavable side-chain fluorinated polymers which will release PFAAs and disclose the content as precursors.

Hence, the chemical composition of the fluorinated polymers (fluorine content, its distribution inside the fluorinated materials, chemical bonds, presence of oxygen-containing groups) substantially influences on the operation properties of the final polymer, research was conducted on in-depth characterisation of such. (Ivanova & Belova, 2021) provided an overview of methods for the analysis of structure and composition of fluorinated polymers: elemental analysis, spectral (IR, UV-VIS, NMR, XPS, EPR), secondary-ion mass spectroscopic (SIMS) and microscopic (AFM, SEM-EDX).  Time-of-flight(TOF)-SIMS is a relatively well-established technique which can be used directly on the material without requirement of a preliminary sample preparation step. The technique is, however, not used for absolute quantification. The parameters that are mostly determined by TOF-SIMS are: the type of polymer used, the molecular weight and the layer thickness. Chain composition, end groups and molecular weight can also be determined using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) (Karis et al., 2002). Other methods like atmospheric solids analysis probe mass spectrometry (ASAP-MS) (Gaiffe et al., 2018) were also applied to characterise polymers using new analytical developments.

However, all these methods are less suited for absolute quantification due to low sensitivity or because they are intrinsicly not quantitative. To quantify total (organic) fluorine content in samples, methods discussed in 3.3.2 can be used.  

3.5 Considerations on the use of methods

Methods can be organised as accredited, standard, validated and research methods, where the former has the most stringent classification. As described in the following chapters a number of accredited methods are present for different matrices, but these don’t cover the complete range of matrices.

It is advised to use an accredited method in an accredited laboratory when this is possible. These methods have been (1) extensively developed and tested, (2) have an inherent quality control guarantee, (3) are cross checked regularly between accredited laboratories and regulatory organs and (4) follow a fixed protocol from which cannot be deviated. This leads to results that can be compared between different laboratories, regions, time points, etc. These accredited methods should however be constantly evaluated and their fit for use should be considered. Continuous improvements of methodologies should be implemented when required.

When an accredited method is not available, it is advised to use a standard or at least a validated method. This validation should be as extensive as possible covering accuracy, precision, linearity and application range, limit of detection (LOD), limit of quantitation (LOQ), selectivity/specificity, recovery and robustness/ruggedness. Extensive validation leads mostly to results with a sufficient confidence to be used for reporting or as with accredited methods to compare between different laboratories, regions and time points.

When new research questions are posed, no standardized or validated methods are available. The developed analytical methods should then be handled with caution and results need further confirmation. Research based analytical methods should be validated as extensive as possible, but complete validation is often not possible.

4. Results of the literature search on analytical methods for PFASs within specific applications/matrices

The following chapter starts with an overview of important aspects related to different matrices considered in this report (Table 1 and Table 2). For each matrix main PFASs used, information on prohibition and restrictions worldwide, available standard methods as well as identified available analytical methods are listed. Subsequently each matrix is covered in a separate chapter providing a detailed assessment for analytical methods. Additionally, PFASs analysis in environmental matrixes, waste and human samples, which were not part of the overview tables due to their complexity, were discussed in the following in more detail.     

Table 1: Overview of analytical methods for PFASs within specific applications/matrices.

^{Note:  [1]https://www.foedevarestyrelsen.dk/english/SiteCollectionDocuments/Kemi%20og%20foedevarekvalitet/UK-Fact-sheet-fluorinated-substances.pdf [2]https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202120220AB1200  [3]https://www.fis-ski.com/en/ski-jumping/ski-jumping-news-multimedia/news/2020-21/ski-wax-only-without-fluorine [4]https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202120220AB652 [5]20 ppm for PFCA/Ss and 1000 ppm for FTOHs. Substances listed in Annex D. Measured with CEN/TS 15968.
https://produktinfo.blauer-engel.de/uploads/criteriafile/en/DE-UZ%20207-201701-en%20Criteria-V4.pdf [6]https://www.collins.senate.gov/newsroom/collins-blumenthal-introduce-bill-ban-PFAS-chemicals-cosmetics#:~:text=Specifically%2C%20the%20No%20PFAS%20in%20Cosmetics%20Act%20would,final%20rule%20to%20be%20issued%2090%20days%20thereafter [7]General ban on PFAS, no limit and analytical testing needs to be stated. https://produktinfo.blauer-engel.de/uploads/criteriafile/de/DE-UZ%20154-201707-de-Kriterien-V8.pdf  [8]Individual substances as stated in this document, no limits and analytical testings stated. https://www.oeko-tex.com/importedmedia/downloadfiles/STANDARD_100_by_OEKO-TEX_R__-_Limit_Values_and_Individual_Substances_According_to_Appendices_4___5_en.pdf [9]Textiles and textile products. Organic fluorine Part 2. Determination of non- and volatile compounds by extraction method using gas chromatography https://www.beuth.de/en/draft-standard/din-en-17681-1/337939568  [10]https://www.beuth.de/en/standard/din-38407-42/137282966}​

Table 2: Overview of analytical methods for PFASs within specific applications/matrices (second part).

^{Note:  [1]https://ec.europa.eu/clima/eu-action/fluorinated-greenhouse-gases/eu-legislation-control-f-gases_en [2]Indirectly as the Blue Angel-label requires that no halogenated blowing agent is used in insulating material https://produktinfo.blauer-engel.de/uploads/criteriafile/de/DE-UZ%20132-202001-de%20Kriterien-V3.pdf above 1000 ppm [3]Indirectly as the Blue Angel-label requires that no halogenated flame retardant is used (above 1000 ppm). in many construction products, for example in insulating material https://produktinfo.blauer-engel.de/uploads/criteriafile/de/DE-UZ%20132-202001-de%20Kriterien-V3.pdf. This method is applicable for solid, pasty and liquid samples with more than 25 ppm. [4]For example in Printers and multifunction devices  https://produktinfo.blauer-engel.de/uploads/criteriafile/de/DE-UZ%20205-201701-de%20Kriterien-2020-07-17.pdf. No chemical testing is needed.}  

4.1 Packaging material, FCM & food & feed processing equipment

Food contact materials (FCM) are materials intended for contact with food during transport, storage, conservation, handling, or manufacture (Ramírez Carnero et al., 2021). PFASs has been widely used in FCM such as fast-food wrappers, microwave popcorn bags, and many more due to their high resistance to degradation even at high temperatures and their water and oil repellence. According to (Glüge et al., 2020), side-chain fluorinated acrylate polymers derived from perfluoroalkane sulfonamide alcohols or fluorotelomer alcohols have become the most widely used polymers in FCM due to their good oil, grease, and water repellence. Additionally, perfluoropolyether-based phosphates and fluoropolymers have become widely used treatments for food contact paper and paper packaging (Glüge et al., 2020). The most common fluoropolymers for non-stick cook- and baking ware has been PTFE, but FEP and PFA are also used in this regard (Glüge et al., 2020). Not only is analysis of the PFASs applied in the articles is important but also the determination of their impurities and degradation products. According to (Glüge et al., 2020), several PFASs^{[1]Perfluoroalkyl carboxylic acids (PFCAs) C_nF_2n+1COOH (n = 3-13), perfluoroalkane sulfonic acids (PFSAs) CnF_2n+1SO₃H (n = 8), (n:2) fluorotelomer alcohols (FTOHs) C_nF_2n+1CH₂CH₂OH (n = 6, 8, 10, 12, 14, 16, 18), (n:2) fluorotelomer phosphate monoester (monoPAPs) C_nF_2n+1CH₂CH₂OP(=O)(OH)₂ (n = 6, 8, 10), (n:2) fluorotelomer phosphate diester (diPAPs) (O)P(OH)(OCH₂CH₂CnF_2n+1)(OCH₂CH₂C_mF_2m+1) (n/m = 6/6, 6/8, 6/10, 6/12, 8/8, 8/10), (n:2) fluorotelomer phosphate triester OP(OCH₂CH₂C_nF_2n+1) (OCH₂CH₂C_mF_2m+1)OCH₂CH₂C_pF_2p+1 (n/m/p = 6/6/6, 6/6/8, 6/8/8, 6/8/10, 6/6/10, 8/8/8) and the polymer PEPE.} have been detected in paper and packaging for food-contact articles. 

Food can be contaminated through FCM containing PFASs. Currently, EFSA has set a new safety threshold for PFASs tolerable weekly intake (TWI) of 4.4 ng/kg of body weight per week.^{[2]https://www.efsa.europa.eu/en/news/pfas-food-efsa-assesses-risks-and-sets-tolerable-intake} During the literature search, many peer-reviewed articles on analysis of PFASs in food or migration studies of PFASs into food have been found. Analysis of food products was excluded in this project as focus has been on the analysis of PFASs in products and on environmental monitoring.

In July 2020, Denmark was the first country that prohibited placement of paper and board FCM in which PFASs have been used on the market, unless a functional barrier is included that prevents the substance from migrating into food.^{[3]https://www.foedevarestyrelsen.dk/english/SiteCollectionDocuments/Kemi%20og%20foedevarekvalitet/UK-Fact-sheet-fluorinated-substances.pdf,[4]https://www.foedevarestyrelsen.dk/english/SiteCollectionDocuments/Kemi%20og%20foedevarekvalitet/FCM%20order%20681%202020.pdf} In this context, the Danish Veterinary and Food Administration has introduced an indicator value of 20 micrograms of organic fluorine per gram of paper that should help the industry assess whether organic fluorinated substances have been added to paper and board. Values below the indicator value are considered as unintentional background pollution.

The state of California also implemented legislation to prohibit PFASs in food packaging and to require chemical disclosures for PFAS content in cookware. The bill prohibits the presence of PFASs in a product or product component at or above 100 ppm, as measured in total organic fluorine (TOF). This bill would require, beginning January 1, 2024, a manufacturer of cookware sold in the state to list the presence of one or more intentionally added chemicals on the product label and include a statement on the product label (and on the product listing for online sales).^{[5]https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202120220AB1200} 

4.1.1 Conclusion for monitoring and compliance measurements

The well-established standard CEN/TS 15968^{[1]Determination of extractable perfluorooctanesulfonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS; German version CEN/TS 15968:2010 https://www.beuth.de/en/pre-standard/din-cen-ts-15968/119731674} is available for determination of PFOS in paper and board FCM by LC-qMS or LC-MS/MS. We assume that this targeted method can be extended to more PFASs, as has already been done for other consumer products (see chapter 4.5). An accredited targeted method for analysis of a broader PFAS substance spectrum was already developed by the Technical University of Denmark (DTU).

To cover all PFASs, measurements of total fluorine, TOF or extractable organic fluorine (EOF) is recommended. Determination of TOF can be realized based on DIN 51723 and EN ISO 10304-1 as proposed by the Danish Ministry.

4.1.2 Analytical measurements

Standards

A standard method CEN/TS 15968^{[1]CEN/TS 15968 - “Determination of extractable perfluorooctanesulphonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS”} is available for determination of PFOS and PFOS related substances^{[2]PFOSA, N-Me-FOSA, N-Et-FOSA, N-Me-FOSE alcohol, N-Et-FOSE alcohol, PFOS salt} in various matrices including papers and cardboards. In this method samples were extracted in methanol prior to MS (LC-qMS or LC-MS/MS).

Established methods used by agencies

In the study “Per- and polyfluorinated alkyl substances (PFAS) in paper and board Food Contact Materials - Selected samples from the Norwegian market 2017” the Technical University of Denmark (DTU) developed in cooperation with the Norwegian Food Safety Authority an accredited analytical method (FC430) for targeted PFASs analyses in paper and board FCM. Targeted PFASs include PFCAs (n = 4-14), PFSAs (n = 4,6,8,10), 6:2 FTSA, (n:2) monoPAPs (n = 6, 8), (n:2) diPAPs (n/m = 6/6, 8/8) and (n:2) FTOHs (n = 4, 6, 8, 10). The method was based on LC-MS/MS of the sample extract (ethanol for PFCAs/PFSAs or 50% ethanol:water for PAPs/FTOHs). However, the FTOHs were not yet covered by accreditation (Granby, 2018).

The Danish Veterinary and Food Administration recommends testing the organic fluorine content in paper and board FCM as TOF or EOF.^{[1]https://www.foedevarestyrelsen.dk/english/SiteCollectionDocuments/Kemi%20og%20foedevarekvalitet/UK-Fact-sheet-fluorinated-substances.pdf} For TOF measurement a method based on the standard DIN EN ISO 10304-1^{[2]DIN EN ISO 10304-1 - “Water quality - Determination of dissolved anions by liquid chromatography of ions - Part 1: Determination of bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate”} is recommended. In this method the paper is burned, whereupon organic fluorine is converted to hydrogen fluorine, which is collected in a liquid and analysed by ion chromatography (IC). For the determination of EOF the organic fluorinated substances can be extracted from the paper material prior to analysis using ethanol. Then, the extract is transferred to a suitable matrix (e.g. microcrystalline cellulose), which can be analysed by the TOF method. The Ministry stated that it is important to ensure that inorganic fluoride is subtracted from the result for both methods because inorganic fluoride that might be present in the article can otherwise cause on error for EOF and TOF determination.

In a follow-up study of a NORAP (Nordic Risk Assessment Project) funded by the Nordic Council of Ministers from 2017, they also used a method for TOF determination that was originally developed for cardboard and paper, as a collaboration between Eurofins and the Ministry of Food, Agriculture and Fisheries of Denmark. The method is also based on EN ISO 10304-1 in combination with DIN 51723^{[3]DIN 51723 – “Testing of solid fuels - Determination of fluorine content”}. In brief, the paper or cardboard materials is shredded, homogenized and pressed into pellets. Then the sample is burned, and combustion gases were absorbed in a Na₂CO₃/NaHCO₃ buffer solution. Fluoride in the solution is measured by IC. They compared TOF values with the sum of detected PFASs by targeted analysis of 22 individual PFASs (PFCAs, PFSAs, FTOHs, FTAs, FOSAs, FOSEs) and pointed out that for most of the samples, the analysed PFASs constituted only a very minor part of the TOF value (below or far below 1%) (Borg & Ivarsson, 2017)

Methods identified by literature research

Targeted analysis of PFASs in FCM have been reported in several peer-reviewed articles. Usually, determination of the PFASs content was performed by LC-MS or MS/MS coupled to a mass spectrometer (MS) or tandem mass spectrometer (MS/MS). In the following an overview of the most common methods and some achievements in method development are given. Many publications focused on targeted analysis of selected PFCAs and PFSAs (PFOA and PFOS are the most common ones). In some articles a broad range of different FCM were analysed for their PFCAs and PFSAs content (Liu et al., 2014; Monge Brenes et al., 2019; Vavrouš et al., 2016; Zafeiraki et al., 2014). Other articles were focusing on method optimization. In this regard, various extraction methods were used and optimized, for example in-tube solid-phase microextraction (SPME) (Dolman & Pelzing, 2011), supercritical fluid extraction (SFE) and/or supercritical carbon dioxide (Sc-CO2) (Chen et al., 2012), pressurized liquid extraction (PLE) (Martínez-Moral & Tena, 2012; Poothong et al., 2012), and focused ultrasound solid–liquid extraction (FUSLE) (Moreta & Tena, 2013). Also, injection and ionization methods were optimized. For example, Lv et al. developed a reactive easy ambient sonic-spray ionization method using a dicationic ionic liquid that can bind anionic analytes and resulting in enhanced sensitivity (19 and 6-fold enhancements in signal intensity for PFOA and PFOS). (Dolman & Pelzing, 2011)   optimized chromatography conditions coupled with ion-trap mass spectrometric detection and improved detection limits with this approach down to 25 pg/mL for PFOA and PFOS  (Dolman & Pelzing, 2011).

Methods combining liquid chromatography in combination with triple quadrupole mass spectrometry (LC-QqQ) and quadrupole time-of-flight mass spectrometry (LC-QTOF) have been developed for targeted analysis, both techniques can detect PFASs at lower levels in the FCM (Ramírez Carnero et al., 2021). For example, a method was reported using PLE and ultra-high performance liquid chromatography (UHPLC) coupled to quadrupole time-of-flight mass spectrometry (QTOF-MS/MS) for analysis of seven PFCAs with limits of detection (LOD) reaching from 0.6 to 16 ng/g (Martínez-Moral & Tena, 2012). (Moreta & Tena, 2014) used FUSLE and UHPLC coupled to quadrupole time-of-flight mass spectrometry (QTOF-MS/MS) for analysis of nine PFCAs and PFOS and achieved very low LODs between 0.2 and 0.7 ng/g.

A very recent publication by (Curtzwiler et al., 2021) presented a science‐based framework for establishing non-intentionally added concentration of PFCAs. They presented a method using contact angle measurement analysis to determine limits of performance (LOP) for PFCAs (n = 4,6,8,10) on the surface of recycled FCM. LOP concentrations for PFCAs ranged from 37 ppm (n = 10) to 1239 ppm (n = 4). They suggest considering these LOP concentrations as non-intentionally added substances for compliance with current and pending regulatory requirements. The authors indicated that future research would broaden the test method to include measurements of other PFAS types, like fluorotelomer, sulfonamide, and fluoropolymer substances. Besides FCM, no other matrix is discussed in the publication and no outlook is given if the described method could be applicable to another matrix.

In addition to PFCAs and PFSAs, also PAPs (Gebbink et al., 2013; Shoeib et al., 2016; Zabaleta et al., 2020) and FTOHs (Kotthoff et al., 2015; X. Liu et al., 2015; Shoeib et al., 2016; Yuan et al., 2016) were analysed in FCM in some peer-reviewed articles. For example, (Gebbink et al., 2013) developed a method for analysis of mono-, di-, and triPAPs using LC-MS/MS. They pointed out that for quantitative analysis of PAPs, compound-specific labelled internal standards showed to be essential as sorption and matrix effects could be observed. FTOHs are usually more volatile and therefore were analysed by different methods: GC-MS (X. Liu et al., 2015), GC-MS with chemical ionisation (GC-CI/MS) (Kotthoff et al., 2015; Shoeib et al., 2016), concurrent solvent recondensation large volume splitless injection (CSR-LVSI) GS-MS (Rewerts et al., 2018), but also LC−MS/MS and/or LC−QTOF−MS (Yuan et al., 2016). (Zabaleta et al., 2016) reported in 2016 a method for analysis of a broad range of various targeted PFASs in FCM (PFCAs, PFPAs, PFOSA, PAPs, FTCAs and FTUCAs) using ultrasonic probe-assisted extraction (UPAE) prior to analysis of the target PFASs by LC-QqQ-MS/MS with method detection limits (MDL) from 0.6–2.2 ng/g. In 2017, they validated a method based on focused FUSLE and a clean-up step with Envi-Carb sorbent and applied the method to the quantification of 24 PFASs (PFCAs, PFSAs, PAPs, FTCAs, FTUCAs) in popcorn bags with MDLs of 0.7–3.5 ng/g (Zabaleta et al., 2017).

Non-targeted analysis of PFASs is usually conducted applying LC-QTOF or LC-QqQ MS. For example, in 2011 (Xenia Trier et al., 2011) developed a screening-method for non-targeted anionic and non-ionic PFASs by high performance liquid chromatography – negative electrospray ionisation – quadrupole time-of-flight mass spectrometry (UHPLC/ESI-QTOF/MS). At a high pH of 9.7, both non-ionic and anionic PFASs were ionised, and a generic approach was used to detect a broad range of PFASs by characteristic mass detects. They applied this method to analyse PFASs in industrial blends FCM and discovered 115 different PFASs including PFOS, PFSA, PFOSA, FTOHs, fluoroacrylate, monoPAPS, diPAPs, triPAPs and PAP-derivatives (X. Trier et al., 2011).

(Ritter et al., 2017) investigated total fluorine (TF) by Particle Induced Gamma Ray (PIGE) in papers and textiles and reported a LOD of 13 nmol F/cm² for papers. In a comprehensive study by (Robel et al., 2017) TF measured by PIGE was compared to the sum of volatile, ionic PFASs and precursors determined by GC-MS and LC-MS/MS and total oxidizable precursor assay (TOPA). The sum of detected PFASs and precursors accounted for a maximum of 16% TF, indicating that most of the fluorine remains associated with the papers and textiles. Also, in another study, quantified PFASs concentrations were very low compared to TF (Schultes et al., 2019). However, in one publication the authors stated that the PIGE method may not be sufficiently sensitive to identify all samples with intentionally added PFASs (Schaider et al., 2017). Other methods for determination of TF that were used for FCM are combustion ion chromatography (CIC), Instrumental neutron activation (INAA) and X-ray photoelectron spectroscopy (XPS) (Schultes et al., 2019; Tokranov et al., 2019). (Tokranov et al., 2019) applied XPS to determine the atomic percent fluorine (% F) in the surficial 0.01 μm of consumer products including FCM. Also, in this study PFASs determined by targeted methods (released in methanol extracts and quantified using LC-MS/MS) typically accounted for <1% of the fluorine measured with XPS. (Schultes et al., 2019) compared the performance of PIGE, CIC and INAA with each other for TF determination of FCM. The results revealed good agreement among all three TF methods. The authors stated that INAA and PIGE has the advantage of being non-destructive, while CIC displayed the lowest detection limits. Furthermore, PIGE as a surface measurement technique can distinguish between coated and uncoated surfaces.

4.2 F-gases and refrigerants including blowing agents

Fluorinated gases (F-gases) are anthropogenic gases that have long atmospheric lifetimes and high global warming potential (GWP). Historically, most F-gases were not considered to be PFASs.  However, in more recent PFAS definitions many F-gases are considered as such. In July 2021 the OECD/UNFP revised their PFAS definition to: “PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS (OECD, 2021).” Based on the broad definition of PFASs, also hydrofluorocarbons would be defined as PFASs. One example is pentafluoroethane (R-125/HFC-125) which is a common HFC used as a refrigerant / fire suppression agent.

Figure 4: Chemical structure of pentafluoroethane (R-125/HFC-125)

Some F-gases are already controlled under the “Montreal Protocol on Substances that Deplete the Ozone Layer”. These substances include chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Most of them are also very potent greenhouse gases.^{[1]https://www.unido.org/our-focus-safeguarding-environment-implementation-multilateral-environmental-agreements/montreal-protocol} The Kigali Amendment to the Montreal protocol aims for the phase-down of hydrofluorocarbons (HFCs) which were currently used as replacements of CFCs and HCFCs. Success is monitored by calculation of control levels for consumption and production data.^{[2]https://ozone.unep.org/sites/default/files/Handbooks/MP-Handbook-2020-English.pdf}

The EU is taking regulatory action to control F-gases as part of its policy to combat climate change: On 1 January 2015 the current Regulation (EU) 517/2014^{[3]https://ec.europa.eu/clima/eu-action/fluorinated-greenhouse-gases/eu-legislation-control-f-gases_en}, the F-gas regulation, was adopted which strengthened the earlier measures and introduced a number of far-reaching changes.

The following three groups of F-gases are addressed in the EU regulatory action plan^{[4]https://ec.europa.eu/clima/eu-action/fluorinated-greenhouse-gases_en}:

• Hydrofluorocarbons (HFCs) that are used in various sectors and applications, such as refrigerants in refrigeration, air-conditioning and heat pump equipment; as blowing agents for foams; as solvents; and in fire extinguishers and aerosols.
• Perfluorocarbons (PFCs) that are typically used in the electronics sector (for example for plasma cleaning of silicon wafers) as well as in the cosmetic and pharmaceutical industry. In the past, PFCs were also used in fire extinguishers and can still be found in older fire protection systems.
• Sulphur hexafluoride (SF₆) is used mainly as an insulating gas, in high voltage switchgear and in the production of magnesium and aluminium.

In addition, in Annex II of the regulation also several other fluorinated greenhouse gases are named that are subject to reporting obligations in accordance with article 19 of the regulation. This includes

• unsaturated hydro(chloro)fluorocarbons (HFOs/HCFOs)
• fluorinated ethers (HFEs) and alcohols
• And other perfluorinated compounds

Since January 2017, the EU Directive 2006/40/EG bans fluorinated refrigerants with a global warming potential of more than 150 in the air-conditioning systems of new passenger cars and small commercial vehicles (the MAC directive). The previous refrigerant tetrafluoroethene (R134a) with a high global warming potential can therefore no longer be used in these new vehicles.

Some refrigerants are also regulated by Regulation (EC) No 1005/2009 of the European Parliament and of the Council of 16 September 2009 on substances that deplete the ozone layer (ODS)^{[5]https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:286:0001:0030:EN:PDF}. This regulation entered into force on 1 January 2010. The Regulation has ensured full compliance with the EU’s obligations under the Montreal Protocol.

4.2.1 Conclusion for monitoring and compliance measurement

F-Gases can be determined analytically by GC-MS, the latest state of the art Medusa GC-MS is measuring 40 species of ODSs and greenhouse gases including several F-gases. During the project, no standard or untargeted method has been found.

4.2.2 Analytical measurements

Established methods

F-gases which are controlled under the Montreal Protocol are routinely monitored by targeted analysis (GC-MS). Worldwide this includes several networks that use their respective method. The Advanced Global Atmospheric Gases Experiment (AGAGE) runs several stations that are coastal or mountain sites around the world chosen primarily to provide accurate measurements of trace gases with lifetimes that are long compared to global atmospheric circulation times. In Europe, stations are located at Switzerland, Italy, Ireland, and Norway. The network developed several systems that have been able to measure atmospheric F-Gases in ambient air by GC-MS. The latest state of the art Medusa GC-MS is measuring 40 species of ODSs and greenhouse gases.^{[1]CF_4, C₂F₆, C₃F₈, c-C₄F₈, C₆F₁₄, SF₆, SF₅CF₃, SO₂F₂, NF₃, HFC-23, HFC-32, HFC-134a, HFC-152a, HFC-125, HFC-143a, HFC-227ea, HFC-236fa, HFC-245fa, HFC-365mfc, HFC-43-10mee, HCFC-22, HCFC-141b, HCFC-142b, HCFC-124, CFC-11, CFC-12, CFC-13, CFC-113, CFC-114, CFC-115, H-1211, H-1301, H2402, CH₃Cl, CH₃Br, CH₂Cl₂, CH₂Br₂, CHCl₃, CHBr₃, CCl₄, CH₃CCl₃, CHCl=CCl₂, CCl₂=CCl₂, COS, C₃H₆, C₃H₈, C₆H₆, C₇H₈, CH₄, N₂O (Source: https://agage.mit.edu/instruments).} More detailed technical information is available online.^{[2]https://agage.mit.edu/instruments/medusa-gas-chromatography-mass-spectrometry-medusa-gc-ms}  

Methods identified by literature search

In this project, several peer-review publications have been found that report worldwide emissions in various locations citing the AGAGE-analysis method (e.g. (Kuyper et al., 2019; S. Li et al., 2011; Yi et al., 2021)). Measurements of perfluoroketones^{[1]Perfluoro-2-methyl-3-pentanone (PF-2M3P), Perfluoro-3-methyl-2-buytanone (PF-3M2B)}, using UV Absorption Spectrum and following quantification using Lamber-Beert´s law is described by (Ren et al., 2019). Also Infrared Absorption Spectra (IR) of methyl-perfluoroheptene-ethers and cyclic PFASs (c-C(5)HF(7) (1H-heptafluorocyclopentene) and c-C(5)F(8) (perfluorocyclopentene) are described in literature (Gierczak et al., 2021; Jubb et al., 2014). Another PFAS-substance that has been measured is trifluoroacetic acid (TFA), that is a degradation product of multiple F-Gases. The acid can be measured (after extraction via denuders and derivatization to the respective acid anilide) in ambient air using GC−MS (Wu et al., 2014).

In this project, for F-gases and refrigerants (including blowing agents), only targeted methods have been identified, while no untargeted analysis method or any method that measures total fluorine has been found.

4.3 Ski Wax

PFASs in ski wax have been used because of their highly water repellent properties that reduces friction between the base of the skis and snow, allowing the skis to glide more freely. More technical details on what kind of wax are used, methods of application, and market data can be taken from the report “PFAS in the treatment of skis — Use, Emissions and Alternatives” prepared by the consultancy wood for the Norwegian Environmental agency in 2021^{[1]https://www.miljodirektoratet.no/sharepoint/downloaditem?id=01FM3LD2TE2M6Z6VKN3NGY6NZO3NW5ZXQE}. In this report it is stated that the main PFASs used in ski waxes are perfluoroalkanes and di-block and tri-block semi-fluorinated n-alkanes (SFAs). Also, fluoropolymers such as perfluoropolyalkylether (PFPAE) are used in some waxes. PFCAs are not thought to have a technical function in the ski waxes but can be present as residual impurities or as degradation products (Nicol et al., 2021). According to (Glüge et al., 2020) predominantly PFCAs, PFSAs, and FTOHs have been detected in ski wax.

In November 2019, the International Ski Federation (FIS) decided to ban the use of fluorinated ski waxes, which have shown a negative environmental and health impact. Such ski waxes are banned for all FIS disciplines from the 2020/2021 season^{[2]https://www.fis-ski.com/en/international-ski-federation/news-multimedia/news/decisions-of-the-fis-council-meeting-in-constance-ger-autumn-2019} on.

4.3.1 Conclusion for monitoring and compliance measurements

In a recent report from KEMI a European standard^{[1]DS/CEN/TS 15968:2010, "Determination of extractable perfluorooctanesulphonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS"} was used successfully for the targeted analysis of PFASs in ski wax. Additionally, extractable organic fluorine (EOF) was determined. This combination of methods may also be explored for enforcement of the PFAS-restriction.

4.3.2 Analytical measurements

Established methods used by agencies

In 2021, the Swedish Chemicals Agency (KEMI) published a report (report in Swedish, summary also available in English) including PFAS-analysis of ski wax (KEMI, 2021). The laboratory has used a method for the analysis of PFOS that is equivalent to the standardised method CEN/TS 15968^{[1]DS/CEN/TS 15968:2010 "Determination of extractable perfluorooctane sulphonate (PFOS) in coated and impregnated solid articles, liquids and fire-fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS"}. It should be noted that this project focussed on checking the compliancy with the POP Regulation^{[2]Regulation (EU) No 2019/1021}. Further, the POP Regulation lays down in paragraph 5 under the relevant entry for PFOS that the standards adopted by the European Committee for Standardisation (CEN) shall be used as test methods to demonstrate that substances, mixtures and articles comply with the requirements of paragraphs 1 and 2 under the same entry^{[3]https://eur-lex.europa.eu/legal-content/EN/TXTtemanord2022-510.pdf?uri=CELEX:32019R1021&rid=3}. As an alternative to the CEN standard, another analytical method leading to equivalent results may be used. In the Swedish study the above-mentioned standard was chosen. For the analysis of ionic and volatile PFASs, the samples were diluted 100 times with acetonitrile before 20 different ¹³C-labelled internal standards were added to the sample extract. The quantification of individual PFASs was done by LC-MS/MS for ionic PFASs and (GC-MS) for volatile PFAS.

The products were also analysed for EOF, using an ion-exchange column and ion chromatography. EOF was measured for information on PFASs that were not included in the targeted analyses and relatively high levels of fluorine were reported. This is in line with the experience that PFASs used in ski waxes are usually perfluoroalkanes, SFAs or fluoropolymers which were not adequately covered by targeted analysis.

Ski wax has been analysed also in two sub projects of the Nordic Risk Assessment Project (NORAP), that analysed in 2012 (highlighting only limited knowledge to PFAS usages and amounts), 2015, and 2017 PFASs in several consumer products (Blom & Hanssen, 2015; Borg & Ivarsson, 2017). The 2015-report highlights the analytical measurement of several ionic PFASs and perfluoroalkyl phosphate esters (PAPs) and volatile PFASs (fluorotelomer alcohol – FTOH), that have been quantified using LC-MS/MS and GC-MS. Nevertheless, no mono or di-PAPs were found in any of the samples analysed in this project. The report published in 2017, revealed that a total organic fluorine (TOF)-method, originally developed for TOF-analysis of paper and packaging, experienced problems with analysis of waterproofing treatment sprays and waxes (Borg & Ivarsson, 2017).

Methods found by literature search

The analysis of PFASs in ski wax is described in several publications: In an exhaustive study of PFASs in a variety of consumer products (Kotthoff et al., 2015) also ski waxes were analysed^{[1]PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFTeDA, PFBS, PFHxS, PFHpS, PFOS, PFDS, 4:2 FTOH, 6:2 FTOH, 8:2 FTOH, 10:2 FTOH, PFOSA}. Depending on the type of PFASs the analytical measurement has been undertaken using LC-MS/MS (PFAAs) or GC-CI/MS (FTOHs). (Fang et al., 2020) described their analysis of 11 best-selling fluorinated ski wax products available in Norway. Ski waxes were analysed for a suite of 26 PFASs, namely; 22 (C4–C25) PFCAs and 4 PFSAs. PFASs were quantified using an ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) instrument.

Semifluorinated n-alkanes have been analysed and found in ski wax as well (Hagenhoff et al., 2018). In comparison to “regular” PFASs, SFAs can also be measured using dielectric barrier discharge in helium for the hyphenation of gas chromatography and mass spectrometry (GC/DBDI-MS).

For fast screening of fluorine on the surface of skis, a new wavelength dispersive x-ray fluorescence spectroscopy (WD-XRF) method was developed and presented at the Dioxin 2018^{[2]38th International Symposium on Halogenated Persistent Organic Pollutants & 10th International PCB Workshop.} (please note that this contribution has not been peer-reviewed) (Schlabach et al., 2018). The authors recommended this method as appropriate tool for control of fluorinated compounds in products surface-treated with fluorinated waxes. The same technique can be also utilized in a handheld XRF as introduced by Bruker. The company claims, that XRF is a multi-element analysis technique which is fast, non-destructive, straightforward to use, and can be taken anywhere testing is needed for in-situ measurements of ski wax (and other matrices).^{[3]https://www.bruker.com/de/news-and-events/webinars/2021/handheld-xrf-measurements-of-fluorine.html}

As shown above, a small number of peer-review articles describe analytical measurements of PFASs in ski wax. In addition, there are also measurements of occupational exposure of professional ski waxers (Freberg et al., 2014; Nilsson et al., 2013). However, as these do not focus on the ski wax product itself, these publications and their respective measurements will not be discussed here.

4.4 Medical devices and medicinal products

PFASs are widely used in medical devices and medicines because of their unique inertness and resistance, which is predominantly applicable on medical devices. Medical devices cover a broad range of products used for treatments like for example bandages, catheters, stents and needles while a medicinal product is a substance or combination of substances that is used for the treatment or prevention of diseases in human beings. Different PFASs are used for those two groups and thus different analytical methods need to be considered,   

A comprehensive overview on medical utensils (covering medical devices and medicinal products) is given by (Glüge et al., 2020). Analysis of active pharmaceutical ingredients (API) (fulfilling the PFAS definition) is outside of this work as such substances are only relevant as PFASs after degradation in the environment with formation of non-degradable PFAS end products. In their non-degradable state, fluorinated carbons act rather as functional groups for pharmaceutical activity.

In medical devices fluoropolymers have been commonly used. PTFE and others have been used as films, filtration membranes, reaction vessels, stirrers, and other components in the pharmaceutical industry (and any other laboratory). Also, in dialysis material (incl. parts of the machines), catheters, stents and needles fluoropolymers are used as they provide low-friction behaviour and clot-resistant coatings. Additionally, the PFASs substance, 1-bromoperfluorooctane (CAS No. 423-55-2) has been used as a processing aid in the manufacture of “microporous” particles for medical devices and especially as contrast agent (classified as medical device) for various techniques like magnetic resonance imaging as well as proton and ¹⁹F NMR.

In medicine, PFASs have been used as anaesthetic (F-gases). Furthermore, some PFASs (e.g. perfluorocarbons) have a huge capacity to dissolve gases and were therefore used in medicinal products. (Glüge et al., 2020) indicates the use of perfluorohexyloctane (CAS No. 133331-77-8) in eye drops. Compared to water, perfluorodecalin has a 1000-fold increased molecular solubility of O₂ (to blood still 50-fold) (Jägers et al., 2021). This oxygen capture property allows PFASs to be used as biocompatible, synthetic oxygen carriers for example in (i) cancer therapeutics, (ii) as blood substitutes or (iii) for organ preservation (isolated organs and during angioplasty) and (iv) diving disease. In this usage PFAS-based liquids/emulsions are also called “white blood”.

4.4.1 Conclusion for monitoring and compliance measurements

During the project no analytical standard or publication has been found that specifically measures PFASs in medical devices or medicines. However, it can be assumed that fluoropolymers used in medical devices can be determined by total fluorine-based methods whereas monomeric PFASs can be detected by targeted LC- and GC-MS. Further research is necessary to ensure appropriateness of the analytical methods. 

4.4.2 Analytical measurements

During this research no relevant information has been found that covers specifically the analysis of PFASs in medical devices or medicines.

Based on the substances as identified by (Glüge et al., 2020), it can be assumed that the fluoropolymers used in medical devices can be measured quantitively as TOF and be characterized by diverse techniques like IR, UV-VIS, NMR, XPS, EPR, SIMS, AFM and SEM-EDX.

Also, common, monomeric PFASs are expected to be analysed by GC- and LC-MS although the sample preparation will depend on the matrix. The detection of PFASs related to in-body-usage can be assumed to be similar to the techniques described under the human biomonitoring chapter 4.18.2.

4.5 Consumer products

A variety of consumer products are known to contain PFASs. In a recent review by (Glüge et al., 2020) the following use categories have been identified: apparel (textiles), food contact material (FCM), cleaning mixtures (including windshield wiper fluids), waxes and polishes, personal care products & cosmetics, and others. Please note, that in this report some use categories are covered in alone standing chapters. For textiles please refer to chapter 4.9, for food contact material refer to chapter 4.1, for ski wax refer to chapter 0, and finally for personal care and cosmetics refer to chapter 4.8.  

In California, a first-in-the-nation prohibition on the use of PFASs in juvenile products^{[1]https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202120220AB652,[2]“Juvenile product” means a product designed for use by infants and children under 12 years of age, including, but not limited to, a baby or toddler foam pillow, bassinet, bedside sleeper, booster seat, changing pad, child restraint system for use in motor vehicles and aircraft, co-sleeper, crib mattress, floor playmat, highchair, highchair pad, infant bouncer, infant carrier, infant seat, infant sleep positioner, infant swing, infant travel bed, infant walker, nap cot, nursing pad, nursing pillow, playmat, playpen, play yard, polyurethane foam mat, pad, or pillow, portable foam nap mat, portable infant sleeper, portable hook-on chair, soft-sided portable crib, stroller, and toddler mattress. Bill does not extend to toys, medical devices, electronic products or internal components "that would not come into direct contact with a child’s skin or mouth during reasonably foreseeable use and abuse of the product".} sold in the state has been signed in October 2021. Under the recently adopted measure (AB 652), companies will be prohibited beginning 1 July 2023 from selling or distributing an array of products intended for children under the age of 12 if they contain PFASs. The presence of PFASs is limited to 100 ppm, or if they have been intentionally added to serve a functional or technical effect. The content of PFASs is measured as total organic fluorine (TOF).

4.5.1 Conclusion for monitoring and compliance measurements

Consumer products have been subjected to targeted PFASs-analysis described in various scientific articles. There is also a standard method CEN/TS 15968 available that measures the extractable PFOS in coated and impregnated solid articles and liquids. This method is in practice also applied for other PFASs than PFOS.

However, when the reported levels of targeted and non-targeted analyses are compared, a significant difference between the levels is found. For surface coated consumer articles there is also the possibility to measure fluorine via X-ray photoelectron spectroscopy (XPS).

4.5.2 Analytical measurements

Standards/ Methods commercially available

One current standard (PD CEN/TS 15968:2014-01-31^{[1]CEN/TS 15968 – “Determination of extractable perfluorooctanesulfonate (PFOS) in coated and impregnated solid articles, liquids and firefighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS”}) focuses on the determination of extractable PFOS in coated and impregnated solid articles and liquids, that has been used for example in the recent KEMI-report. Therein compliancy of consumer articles with the POP Regulation has been checked. A variety of commercial laboratories offer to check compliancy with REACH and the POP Regulation regarding PFAS. For example, Eurofins or Agrolab advertise on their homepages PFASs analysis of consumer products besides a broad variety of environmental matrices^{[2]https://www.agrolab.com/en/service/download/document-search/776-agrolab-group-product-information-aof-pfas/file.html,[3]https://cdnmedia.eurofins.com/eurofins-us/media/1710450/pfas-user-guide_final.pdf}. These methods include targeted PFASs analysis according to EPA/DIN/EN standards, Total Oxidizable Precursors Assay (TOPA) and methods to determine total (organic) fluorine as AOF/TOF/EOF. According to Agrolab, the determination of additional sum parameters offers the possibility to complement the single-substance LC-MS/MS PFASs determination.

Established methods used by agencies

As already mentioned in other sub sections of this report, in 2021, the Swedish Chemicals Agency (KEMI) published a report (report in Swedish, summary also available in English) including PFASs-analysis of several consumer articles (KEMI, 2021). This included various products like for example hardwood floor finishes, bike lubricants (see chapter 4.11), ski waxes (see chapter 0), waterproofing spray, household fire extinguisher (see chapter 4.7), and textiles (see chapter 4.9). Accordingly, in this chapter only hardwood floor finishes and waterproofing sprays will be discussed. They used a method for the analysis of PFOS that is equivalent to the standardised method CEN/TS 15968^{[1]CEN/TS 15968 "Determination of extractable perfluorooctane sulfonate (PFOS) in coated and impregnated solid articles, liquids and firefighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS".}. It should be noted that this project focused on checking the compliancy with the POP Regulation. For the analysis of ionic and volatile PFASs, the samples were diluted 100 times with acetonitrile before 20 different ¹³C-labelled internal standards were added to the sample extract. The quantification of individual PFASs was performed by LC-MS/MS for ionic PFASs and GC-MS for volatile PFASs. The products were also analysed for extractable organic fluorine (EOF), using an ion-exchange column and ion chromatography (IC). Relatively high levels of fluorine (mg F/kg sample) were measured in many products using the EOF method and considerably higher than the sum of individual PFAS measurements. This indicates that there is a large under-reporting of PFASs because the targeted analyses have only been able to identify a few substances.

Also, the measurement of consumer products with sum parameters (total organic fluorine, TOF) is described. Two Nordic Council reports from 2015 and 2017 highlights the measurement of PFASs in several consumer products like textiles, FCM, ski wax, but also car polish, rinse aids for dishwasher liquids, waterproofing sprays, and dental floss (Blom & Hanssen, 2015; Borg & Ivarsson, 2017). However, for non-liquid products, the method experienced problems as shown by the analysis of waterproofing treatment sprays and waxes.

Methods identified by literature search

Several publications target a variety of consumer articles like textiles (outdoor jackets tec.), carpets, cleaning and impregnating agents, leather samples, baking and sandwich papers, paper baking forms and ski waxes. In the following the most relevant publications of the last 10 years are highlighted.

Targeted PFAS-analysis have recently been reported. In 2019, Lee et al. published a survey on a subset of targeted PFASs (belonging to 11 PFASs which can be divided into PFCAs, PFSAs, perfluorooctane sulfonamides, perfluorooctane sulfonamide ethanol, and FTOHs) in various consumer products (Lee et al., 2019). The articles have been classified according to four types: coated metal wares, textile products, leather products, and household products. From each of the samples PFASs have been extracted by methanol extraction that was conducted for 2 h, followed by filtration and analysis by LC-MS/MS. Of a total of 300 products, PFASs were detected in 51 products above the detection limit, which accounted for approximately 17% of the products tested.

(Meng et al., 2020) reported a screening of 200 hazardous substances in plastic toys using UHPLC-Q-TOF-MS (. Limits of detection (LODs) and quantification (LOQs) for all screened substances are reported to be in the range of 0.01–0.98 mg/kg and 0.03–2.99 mg/kg, respectively (which are relatively high values). However, individual PFAS levels are not reported. Of the 50 plastic toys tested, none contained detectable levels of the analysed PFASs. It is not clear if the high limits of quantification lead to this result.   

In addition, also other earlier published studies analysed targeted PFASs in consumer products using variations of mass spectrometry (Bečanová et al., 2016; Borg & Ivarsson, 2017; Herzke et al., 2012; Kotthoff et al., 2015; Liu et al., 2014; Vestergren et al., 2015; Ye et al., 2015).

According to (Mumtaz et al., 2019)., organic fluorinated surfactants are widely employed in textile finishing agents to achieve oil, water, and stain repellences. This has been regarded as an important emission source of PFASs to the environment. China is the biggest manufacturer of clothes, and thus production of textile finishing agents is also a relevant industrial activity. In the presented study, textile treatment products were investigated by the Kendrick mass defect method. The quantification results demonstrated a significant presence of perfluorooctane sulfonate (0.37 mg/L) in textile treatment manufactured by electrochemical fluorination technology. The products obtained by short-chain PFAS-based telomerization were dominated by PFOA (mean concentration: 0.29 mg/L), whose values exceeded the limits stated in the European Chemical Agency guidelines (0.025 mg/L). Moreover, TOPA indicated high levels of indirectly quantified precursors with long alkyl chains (C7–C9). Together, these results suggest that there is currently a certain degree of environmental and health risks in China that originates from the utilization of textile finishing agents, and better manufacturing processes are required to reduce such risks.

Another approach is undertaken by (Tokranov et al., 2019) who describe the usage of X-ray photoelectron spectroscopy (XPS) to determine the atomic percent fluorine (% F) in the surficial 0.01 μm of consumer products. The consumer products tested are predominantly textiles and FCM, but also bandages, lens wipes, mask, folder, label, a notebook cover, and a shower curtain. Also, in this study PFASs released in methanol extracts and quantified using LC-MS/MS typically accounted for <1% of the fluorine measured with XPS.

4.6 Flame retardants & resins

Fluorine-containing flame retardants are less used in practice because they do not intervene in the combustion process at the right time in contrary to other halogenated flame retardants like brominated ones that are commonly used. It is believed that in brominated flame retardants the effective agent hydrogen bromide, HBr, is liberated in a narrow temperature range so that it is present in high concentration in the flame zone. Fluorine cannot act as a radical scavenger in the gas phase because of its strong bond to carbon (Maier & Schiller, 2016).

However, PFASs are used as flame retardants in some cases, and according to (Glüge et al., 2020) PFASs are applied in polycarbonate resins and other plastics as flame retardants. KPFBS, the potassium salt of PFBS, is marketed as flame retardants for polycarbonate resins used in electronics.^{[1]https://www.oecd.org/chemicalsafety/risk-management/synthesis-paper-on-per-and-polyfluorinated-chemicals.htm and https://additives.ulprospector.com/datasheet/e258274/biofr-kpbs} This usage is also marketed on the internet by a Chinese company^{[2]https://additives.ulprospector.com/datasheet/e258274/biofr-kpbs}. Also, PTFE is used as an anti-dripping agent (substances that prevent burning plastic from dripping off). This has been described in literature (Zhan et al., 2014) and on sites of commercial providers^{[3]For example https://www.european-additives.com/anti-dripping-agents.html}.

4.6.1 Conclusion for monitoring and compliance measurements

The usage of PFASs as a flame retardant is reported for plastics (polycarbonate used in electronics). However, based on the stability of the C-F-bond PFASs are generally less used for this application. No specific analytical method for determination of PFASs in flame retardants was found during the project, but we assume that methods used for other matrices (e.g. consumer products) can also be applied to this matrix.

4.6.2 Analytical measurements

During this research no specific analytic method for the detection of PFASs in flame retardants or resins were found. Methods used for PFASs analysis in other plastics (e.g. in consumer products in section 4.5, construction products in section 4.13) can potentially also be applied for this matrix. Other industrial applications are discussed in several other chapters of this report (e.g., lubricants in 4.11).

4.7 Fire Fighting Foams

PFASs are used in aqueous film-forming foams (AFFF) and alcohol-resistant aqueous film-forming foam (AR-AFFF) as film formers (a thin layer of PFASs solution that “sits” on top of the fuel and below the foam blanket due to its low surface tension.) and stabilizers by lowering the surface tension of water (Glüge et al., 2020). Firefighting foam is applied by mixing foam concentrate and water to make the firefighting foam solution, which typically contains less than a percent of fluorinated surfactants once in mixture. When applied to a fire, the foam solution is aerated at the nozzle, yielding finished firefighting foam (ITRC, 2021).

The types of PFASs in firefighting foams vary by year of production and manufacturer (Dauchy et al., 2017). Over the last decades, the utilization of different PFAS classes changed over time, what can be attributed to regulatory action (e.g. Stockholm Convention) and voluntary phase-outs. In addition, also the production processes changed from electrochemical fluorination (ECF)-derived to telomer-derived firefighting foams. The ECF process results in a PFASs mixture dominated by PFAAs—both PFSA and PFCA homologues, while the telomerization process exclusively produces foam formulations consisting of polyfluorinated compounds. ECF-based AFFF formulations (e.g. PFOS) were voluntarily phased out of production in the United States in approximately 2002. Fluorotelomer foams have been in use since the 1970s and became the predominant foam after 2001, when the major manufacturer (3M) of long-chain ECF-based foams (legacy PFOS foam) discontinued production (ITRC, 2021).

4.7.1 Conclusion for monitoring and compliance measurements

From an analytical viewpoint, fire-fighting foams are to be treated as liquid aqueous samples that contain very high concentration of PFASs. As a consequence, foam formulations are in practice diluted and then analysed like regular aqueous samples. For targeted PFASs analysis with a specific subset of PFASs, these measurements include standards that are widely used from authorities (US EPA) and technical specifications. For non-targeted analysis, measurements of Total Organic Fluorine (TOF) and Total Oxidizable Precursors Assay (TOPA)are well established and are provided by laboratories. The NGO-label “GreenScreen Certified™ for Firefighting Foam” defines “PFAS-free” as zero intentionally added PFASs to the product and additionally PFASs contamination in the product must be less than 1 ppm as measured as TOF.

4.7.2 Analytical measurements

Standards

As described above PFOS has been a major component of AFFF in the past. The technical specification CEN/TS 15968^{[1]DIN CEN/TS 15968 “Determination of extractable perfluorooctanesulfonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS; German version CEN/TS 15968:2010” https://www.din.de/en/getting-involved/standards-committees/nmp/publications/wdc-beuth:din21:119731674?destinationLanguage=&sourceLanguage=} describes the determination of extractable PFOS in coated and impregnated solid articles, liquids and firefighting foams by LC-qMS or LC-MS/MS.

Established methods used by agencies and commercial laboratories

According to ITRC, AFFF formulations are to be considered as samples that are known to contain high concentration of PFASs (ppm) and can be subjected to a serial dilution if needed. The diluted samples can then be analysed by US EPA Method 533^{[1]Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry. EPA/815-B-19-20  https://www.epa.gov/sites/default/files/2019-12/documents/method-533-815b19020.pdf} and/or Method 537.1^{[2]Determination of Selected Per- and Polyflourinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=348508&Lab=CESER&simpleSearch=0&showCriteria=2&searchAll=537.1&TIMSType=&dateBeginPublishedPresented=03%2F24%2F2018}. Method 533 tests for 25 PFAS analytes (16 PFAAs and 9 other PFASs, including HFPO-DA (a GenX process chemical) and ADONA. Method 537.1 tests for 18 PFAS analytes (12 PFAAs and 6 other PFASs, including HFPO-DA (a GenX process chemical). In this method surrogates are added prior to solid-phase extraction (SPE) to assess for analyte loss due to sample preparation. Internal standards are added to the final sample extract to assess instrument performance. US EPA Methods 537 and 533, call for PFASs extraction from water using SPE.

The US Department of Defense (DoD) offers guidance on the analysis of PFASs in firefighting foam in terms of a comprehensive set of quality standards for PFASs analysis^{[3]Appendix B, Table 15 of the report “Quality Systems Manual (QSM) for Environmental Laboratories” https://denix.osd.mil/edqw/documents/manuals/qsm-version-5-3-final/}.

There is also a certification mark licensed by the NGO Clean Production Action called “GreenScreen Certified™ for Firefighting Foam” that defines PFAS-free as zero intentionally added PFASs to the product and TOF in the product must be less than 0.0001 percent by weight of the product (1 ppm) as measured by combustion ion chromatography (CIC).

A variety of laboratories offer testing of firefighting foams for PFASs, including measurements according to US EPA method 537^{[4]https://cdnmedia.eurofins.com/eurofins-us/media/1710450/pfas-user-guide_final.pdf}. In addition, several laboratories offer to analyse diluted fire-fighting foam samples by TOPA. Information available shows that the concentration of the AFFF can affect both qualitative and quantitative outcome of the oxidation process^{[5]https://www.alsglobal.com/-/media/als/resources/services-and-products/environmental/data-sheets-canada/pfas-by-top-assay.pdf}.

Methods identified by literature search

The analysis of PFASs in firefighting foams is still a topic of interest in the scientific community. This is likely based on the fact that the release of PFAS-containing fire-fighting foams is the biggest source of PFASs to the environment. A variety of different techniques and technical set-ups is discussed in many scientific publications. In the following the most relevant techniques of the last 10 years are introduced. Those publications which “just” report PFAS-levels measured by techniques above will not be highlighted.

A recent publication from (Ruyle et al., 2021), combines targeted PFASs analysis (according to US EPA method 533 as described before), total fluorine analysis, non-targeted PFASs analysis, TOPA and finally a method quantifying oxidizable precursors using Bayesian Inference. The authors claim that the method comparisons performed allow to validate the fluorine mass balance in AFFF and create a priority list of the most abundant suspect precursors. Results show that virtually all (median 104 ± 19%) Extractable Organic Fluorine (EOF) in contemporary and legacy AFFF consists of targeted compounds and oxidizable precursors, 90% of which are 6:2 fluorotelomers in contemporary products.

(Dubocq et al., 2020) are combining target analysis, non-target screening analysis, total fluorine, and inorganic fluoride (IF) measurement. This combination was applied to disclose the chemical composition of 24 foams intended for liquid fires. The results show that based on the mass balance, the known organic fluorine accounted for <1% in most fluorine containing AFFFs. Also, these authors further found that the unknown PFASs is mainly based on 6:2 fluorotelomers.

The result showing that contemporary AFFF consist mainly of 6:2 fluorotelomers is in line with earlier studies, for example (Fang et al., 2015; Weiner et al., 2013; Yi et al., 2018).

(Place & Field, 2012) described already in 2012, the identification of (at that time) novel fluorochemicals in AFFF using fast atom bombardment mass spectrometry (FAB-MS) and high-resolution quadrupole time-of-flight mass spectrometry (qTOF-MS) to elucidate chemical formulas for the fluorochemicals in AFFF mixtures. By this the authors identified anionic, cationic, and zwitterionic surfactants with perfluoroalkyl chain lengths ranging from 4 to 12.

This was further developed by (Backe et al., 2013), who used nonaqueous (methanol) large-volume injection LC-MS/MS. (D’Agostino & Mabury, 2014) also described the combination of several analytical techniques (qTOF-MS, FTICR-MS, TOF-CIC, LC-MS/MS,) aiming at the structural identification of PFASs used in AFFF. Other studies describe the usage of qTOF-MS as well in combination with TOPA and also found high amounts of unidentified PFASs (Boiteux et al., 2017; Dauchy et al., 2017). (Barzen-Hanson et al., 2017) described the analytical determination of 40 newly identified PFAS classes using a qTOF-MS. Favreau et al. published in 2017 further PFASs measurements in AFFF (and other liquid commercial products) (Favreau et al., 2017). The measurements were, once again, based on LC- and GC-MS/MS.

Fluorotelomers (FTOHs) are volatile and can be subjected to other analytical methods than non-volatile PFASs. This concept has been taken up by (Riedel et al., 2019), who worked with the direct volatilization of samples without prior processing, allowing for fast measurements and reduced sample treatment compared to established methods. (Luo et al., 2020) described in 2020 the rapid characterization of both known and unknown PFASs in AFFF by a combination of liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS). (Yukioka et al., 2020) published in 2020 a new method to search for PFASs by linking fragmentation flags with their molecular ions by drift time using ion mobility spectrometry. In this publication a household fire extinguisher liquid was analytically tested for PFASs but no PFASs were quantified.

Two alternative methods for the analysis of PFASs in firefighting foam were described in (Cheng Fang et al., 2016) and (C. Fang et al., 2016): the usage of surface-enhanced Raman scattering (SERS), and potentiometric measurements.

4.8 Cosmetics

PFASs are used in cosmetic and personal care products to make creams and lotions penetrate the skin more easily, make the skin brighter, make the skin absorb more oxygen, or make the make-up more durable and weather resistant (Glüge et al., 2020). In this regard, PFASs have been used for example in foundation, moisturizer, eyeshadow, mascara, shaving cream, powder and lipstick.

Ingredients in cosmetics must be declared on the packaging according to the International Nomenclature of Cosmetic Ingredients (INCI) (see also the Cosmetic Ingredient (CosIng) database^{[1]https://ec.europa.eu/growth/sectors/cosmetics/cosmetic-ingredient-database_en}). A broad range of PFASs have been used or detected in cosmetics including PFCAs, FTSs, PAPs, fluoropolymers (e.g., PTFE) and many more. A detailed list of PFASs divided into various cosmetic product groups can be found in (Glüge et al., 2020).

PFASs are planned to be included in the EU ecolabel^{[2]https://meta.eeb.org/2021/05/27/new-eu-ecolabel-to-tackle-cosmetics-greenwashing/}. The German ecolabel “Blauer Engel”^{[3]https://produktinfo.blauer-engel.de/uploads/criteriafile/de/DE-UZ%20203-202001-de%20Kriterien-2020-06-25.pdf} and the “Nordic Swan”^{[4]https://api.svanemerket.no/api/docs/CriteriaDocuments/ProductGroup/090?fileType=1&language=d} already contain a prohibition on the use of PFASs in cosmetic products, however, there is no information on the analytical testing given. Some commercial laboratories offer measurement of targeted PFASs in cosmetics. For example, one supplier offer analysis of PFOA, PFNA, PFDeA, PFUnA, PFDoA, PFTrA, and PFTA with a LOQ of 2.5 ng/g.^{[5]https://cdnmedia.eurofins.com/european-west/media/12153216/ef-cpc-flyer-pfas.pdf} There are no information on the analytical method available.

In California the toxic-free cosmetics act, also known as Assembly Bill 2762, bans certain long-chain PFAS^{[6] (A) Perfluorooctane sulfonate (PFOS); heptadecafluorooctane-1-sulfonic acid (CAS no. 1763-23-1); (B) Potassium perfluorooctanesulfonate; potassium heptadecafluorooctane-1-sulfonate (CAS no. 2795-39-3); (C) Diethanolamine perfluorooctane sulfonate (CAS 70225-14-8); (D) Ammonium perfluorooctane sulfonate; ammonium heptadecafluorooctanesulfonate (CAS 29081-56-9); (E) Lithium perfluorooctane sulfonate; lithium heptadecafluorooctanesulfonate (CAS 29457-72-5); (F) Perfluorooctanoic acid (PFOA)(CAS no. 335-67-1); (G) Ammonium pentadecafluorooctanoate (CAS no. 3825-26-1); (H) Nonadecafluorodecanoic acid (CAS no. 355-76-2; (I) Ammonium nonadecafluorodecanoate (CAS no. 3108-42-7); (J) Sodium nonadecafluorodecanoate (CAS no. 3830-45-3); (K) Perfluorononanoic acid (PFNA)(CAS no. 375-95-1); (L) Sodium heptadecafluorononanoate (CAS no. 21049-39-8); (M) Ammonium perfluorononanoate (CAS no. 4149-60-4).}, as intentionally added substances, from cosmetics and personal care products sold or made in the state.^{[7]https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201920200AB2762} 

4.8.1 Conclusion for monitoring and compliance measurements

There is currently no standard method for determination of PFASs in cosmetics available, but some commercial laboratories offer analysis of some targeted PFASs. In some studies, measurements of total fluorine (TF), total organic fluorine (TOF) or extractable organic fluorine (EOF) showed much higher values than determined by targeted PFASs analysis. Therefore, analysis of targeted PFASs might not disclose the full picture of PFASs used or present in the products.

4.8.2 Analytical measurements

Established methods used by agencies and commercial laboratories

In a report “Risk assessment of fluorinated substances in cosmetic products” published in 2018 by the Danish Environmental Protection Agency, cosmetic products have been analysed for selected targeted PFASs (PFCAs, PFSAs and FTS) and total organic fluorine (TOF).^{[1]https://www2.mst.dk/Udgiv/publications/2018/10/978-87-93710-94-8.pdf} Targeted PFASs analysis was done by LC-MS/MS and determination of TOF by ion chromatography. They found much higher values of TOF than for individual PFASs and assumed that the relatively simple fluoroalkyl substances, which were determined quantitatively, are probably derived primarily from impurities from production and degradation of precursors, as the free acids themselves are rarely (if at all) used in cosmetic products. Based on the target analysis they did a hazard assessment for some of the targeted PFASs measured.

In a study by a Norwegian NGO, 15 cosmetic products from various suppliers were analysed for some targeted PFASs (PFAAs, diPAP, FTOH, FTS) by LC-MS. The report is in Norwegian, but in a table measured PFAS values are given.^{[2]https://www.framtiden.no/bilder/dokumenter/bakgrunn_kosmetikk_mars2018.pdf} 

Methods identified by literature research

Up to now, there is only a small number of studies available that describe analytical measurements of PFASs in cosmetics. In general, targeted analyses of selected PFASs can be done by liquid or gas chromatography coupled to mass spectrometry (LC-MS or GC-MS). (Fujii et al., 2013). analysed PFCAs (C6-C14) in personal care products (e.g. manicure, lip rouge, powder foundation) and sun cream by GC-MS with electron-capture negative ionization (GC/ECNI-MS).

In a recent publication by (Whitehead et al., 2021) PFASs in North American cosmetics were investigated. They measured total fluorine content and a broad range of targeted PFASs of eight cosmetic categories based on the intended use including lips, foundation, eyes, mascara, face, concealer, eyebrow and miscellaneous. Total fluorine content was determined by particle-induced gamma-ray emission spectroscopy (PIGE). Targeted analytes were measured by LC-MS/MS (PFCAs, PFSAs, FTCAs, FTSAs, PAP, FOSA and derivates) and GC-MS (FTOHs, FTAc, FTMAc, FOSE derivates). The authors stated that PFASs were listed only in the minority of cosmetic products. Nevertheless, they found high detection frequency by PIGE and concentrations of PFASs measured by targeted analyses. Fluorotelomer alcohols (FTOHs), methacrylates (FTMAs), and phosphate esters (PAPs) were the most frequently detected PFAS. The difference between total fluorine concentrations from PIGE and targeted analyses results was not correlated in this study. The authors pointed out the need for better government oversight of PFASs, including the labelling of all cosmetic products containing these chemicals.

(Schultes et al., 2018) investigated the fluorine mass balance in cosmetic products. They determined targeted PFASs (PFCAs, PFSAs, FOSA, PAPs) by LC-MS/MS, as well as extractable organic fluorine (EOF) and total fluorine (TF) by combustion ion chromatography (CIC). For all samples, the sum of targeted PFAS concentrations only explained a small fraction of the EOF and TF, pointing to the presence of unknown organic and/or inorganic fluorinated substances, including polymers.

In addition, there were peer-reviewed articles found focusing on the outcome (e.g., contamination of environmental water with PFASs from cosmetics (Shaw et al., 2013) or PFASs in serum in association with cosmetics (Thépaut et al., 2021). Those articles were not discussed here as these studies do not focus on analysis of the cosmetic products themselves.

4.9 Textiles

PFASs are widely used in the textile industry for their water-, stain- and oil-repellency (Glüge et al., 2020). Some of the textile products that may contain PFASs include fashion apparel, uniforms, sportswear, outdoor gear, footwear, carpet and rugs, backpacks, swimwear, and upholstery. Also, in the production of leather, fluorinated surfactants have been used to improve the efficiency of hydrating, pickling, degreasing and tanning. According to (Glüge et al., 2020), the most frequently used PFASs in textiles are side-chain fluorinated polymers, whereas long-chain fluorotelomer- or POSF-based derivatives on side-chains have (largely) been replaced with shorter-chain homologues.

At the moment there are no regulations for PFASs as a group for textiles. The Department of Toxic Substances Control (DTSC) in California initiated rulemaking to list treatments containing PFASs for use on converted textiles or leathers such as carpets, upholstery, clothing and shoes as a Priority Product under the Safer Consumer Products (SCP) regulation.^{[1]https://dtsc.ca.gov/scp/treatments-with-pfass/} Also, the textiles sector is currently considered in The Strategic Approach to International Chemicals Management (SAICM) context through the ‘Chemicals in Products Programme’. In a report “Engaging the textile industry as a key sector in SAICM – A review of PFAS as a chemical class in the textile sector” from 2021 by the Natural Resources Defense Council (NRDC) it is stated that regular and reliable testing is the key to make sure that all PFASs are eliminated from non-essential products. However, the authors pointed out that available testing methods for identifying the total amount of all PFASs in textile products are currently limited.^{[2]https://www.saicmknowledge.org/sites/default/files/publications/SAICM%20report_PFAS%20in%20Textile_final_May%202021.pdf}

The market has already adopted voluntary regulations for PFAS limit values in the textile and leather sectors, for example the Standard 100 from OEKO-TEX®.^{[3]https://www.oeko-tex.com/importedmedia/downloadfiles/STANDARD_100_by_OEKO-TEX_R__-_Standard_en.pdf} 

4.9.1 Conclusion for monitoring and compliance measurements

Textiles is one of the matrices for which standards are available for targeted PFASs analyses: ISO 23702-1 for non-volatile PFASs in leather by LC-MS/MS, DIN 17681-2 for volatile PFASs in textiles by, e.g. GC-MS/MS, CEN TS 15968 for determination of PFOS and derivates. To cover all PFAS, measurements of total fluorine, TOF or EOF is recommended. For example, determination of TOF can be realized like recommended for FCM based on DIN 51723 and EN ISO 10304-1.

4.9.2 Analytical measurements

Standards

Standard methods are available to determine targeted PFASs in textile and leather:

• The ISO standard 23702-1 was developed for determination of non-volatile PFASs in leather.^{[1]ISO 23702-1:2018 - Leather — Organic fluorine — Part 1: Determination of the non-volatile compound content by extraction method using liquid chromatography/ tandem mass spectrometry detector (LC-MS/MS)} PFASs were extracted from the sample with methanol and analysed by LC-MS/MS. This method focuses on targeted analysis of long-chain PFAS (C7 to C14) but can also be adopted to other PFASs after analytical evaluation.
• For determination of PFOS and derivatives in coated and impregnated solids the CEN standard TS 15968 is available.^{[2] CEN/TS 15968:2010 - Determination of extractable perfluorooctanesulphonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting}
• Additionally, a draft DIN standard 17681-2 is available for determination of volatile PFASs in textiles (fibres, yarns, fabrics) by gas chromatography (GC-MS/MS, GC-MS/PCI or GC-MS/EI) after extraction with methanol.^{[3]DIN EN 17681-2 - Textiles and textile products - Organic fluorine - Part 2: Determination of volatile compounds by extraction method using gas chromatography https://www.beuth.de/de/norm-entwurf/din-en-17681-1/337939568} This method can be applied to PFOA, its salts and PFOA-related compounds, namely Me-PFOA, Et-PFOA, 6:2 FTA, 8:2 FTA, 10:2 FTA, 6:2 FTMA, 8:2 FTMA.

Methods used by commercial laboratories

The commercial supplier Macherey-Nagel developed an application note based on the Standard 100 from OEKO-TEX®.^{[1]https://www.mn-net.com/mediatemanord2022-510.pdf3e/87/76/AN-07-2020-SPE-of-PFAS-from-clothing-EN.pdf} The method includes determination of 40 PFASs from several textile types based on the methodology of DIN standard 38407-42^{[2] DIN 38407-42 “German standard methods for the examination of water, waste water and sludge - Jointly determinable substances (group F) - Part 42: Determination of selected polyfluorinated compounds (PFC) in water - Method using high performance liquid chromatography and mass spectrometric detection (HPLC/MS-MS) after solid-liquid extraction (F 42)”} for PFASs in waste. Also, some laboratories offer PFASs analysis for textiles, e.g. when testing chemical product safety for textiles and sport goods by a complete range of analytical parameters to rule out undesired substances including PFASs.^{[3]https://www.galab.com/2020/05/08/pfos-and-pfoa-in-textiles-sports-goods/} 

Established methods used by agencies

There are several reports of authorities that have determined PFAS levels in textiles. Two more recent studies are discussed in the following (more studies can be found in the attached excel sheet). In one study from 2015 by the Danish Environmental Protection Agency, total fluorine content and targeted PFASs in textiles for children were determined. Targeted PFASs in the study included 39 substances from various substance classes (PFSAs, PFCAs, FTCAs, FTACs, FTMACs, FTOHs, FTSAs, FASAs, MeFASAs, MeFASEs, EtFASAs, EtFASEs) and were measured by LC-MS/MS and GC-MS.^{[1]https://www2.mst.dk/Udgiv/publications/2015/04/978-87-93352-12-4.pdf} Total fluorine was determined by ion combustion. The study showed that the non-polymeric PFASs account only for about 0.04% (average) of the fluorine content of textile. They suppose that the remaining part is present in the polymers in the form of polyfluoroalkyl-based side-chains and pointed out that there is considerable uncertainty about the extent to which these side-chains can be split off from the polymers in use, washing and disposal of the clothes.

The Nordic Council published in 2017 a report on “Analysis of PFASs and TOF in products” in which they analysed several consumer products, including textiles.^{[2]https://norden.diva-portal.org/smash/get/diva2:1118439/FULLTEXT01.pdf} 22 targeted PFASs (PFCAs, PFSAs, FTOHs, FTAs, FOSAs, FOSEs) were determined by LC-MS/MS after ultrasonic extraction. Additionally, they measured the TOF content by a method that was developed for cardboard and paper based on DIN 51723 and EN ISO 10304-1 (for more information see FCM subchapter 4.1). It was highlighted in the report that the comparisons between the sums of detected PFASs and the TOF concentrations showed that for most samples the analysed PFASs constituted only a very minor part of the TOF (below or far below 1%).

Methods identified by literature research

Several peer-reviewed articles have been found that have determined PFASs in textiles. In most of the publications they measured various consumer products. Therefore, there is a considerable overlap with chapter 4.1 (FCM) and 4.5.2 (consumer articles). Indirect measurements, e.g. dust in clothing shops (Wu & Chang, 2012) or effects of weathering and laundering (Dolan & Jorabchi, 2021; van der Veen et al., 2020) are not further discussed. Analytical methods are briefly summarized in the following.

Targeted analyses of PFASs (PFCAs, PFSAs, FTOHs, FTSs, etc.) have been determined by chromatography (LC or GC) coupled to mass and tandem mass spectrometry after extraction from textile samples. The most common extraction methods used are solvent extraction (usually with methanol) (Bečanová et al., 2016; Gremmel et al., 2016; Herzke et al., 2012; Supreeyasunthorn et al., 2016; van der Veen et al., 2016) and ultrasonication in solvents (X. Liu et al., 2015; Rewerts et al., 2018; Schlummer et al., 2013). Examples for other extraction methods are supercritical fluid extraction (SFE) (Chen et al., 2012), supramolecular solvent (SUPRAS)-based extraction (G. Li et al., 2021), liquid–solid extraction (LSE) (Janousek et al., 2019) and ultrasonic liquid extraction combined with solid-phase extraction (SPE) (Yan Zhang et al., 2018).

Some examples of targeted analyses are given in the following. (Vestergren et al., 2015) analysed 45 consumer products from China for targeted PFAS. Samples consisted of furniture textile, carpet, clothing and FCM. PFCAs and PFSAs were analysed by LC–MS/MS whereas FOSEs, FOSAs and FTOHs were analysed by GC–MS. (Janousek et al., 2019) analysed PFASs in building materials and industrial textiles including textiles for maritime applications. They measured 29 PFASs (chain length in the range of C4–C14) after LSE by LC-MS/MS. (Stróżyńska & Schuhen, 2020) developed a method for the analysis of PFCAs (C4–C12) in solid samples applying derivatisation with N,N-dimethylformamide dimethyl acetal (DMF-DMA) prior to detection by GC–MS. Detection limits of this method were in the range of 0.15–0.38 ng/mL. The authors stressed its simplicity, mild conditions and cost efficiency due to the opportunity to use GC–MS equipment.

In a study by (H. Zhu & K. Kannan, 2020) textile extracts that were analysed by LC-MS/MS after oxidative treatment (TOPA) exhibited PFCAs concentrations 10-fold higher than those in extracts analysed prior to oxidation. Especially commonly incorporated side-chain fluorinated polymers (SFPs) in textiles cannot be measured by standard targeted analysis. They can be measured directly using matrix-assisted laser desorption ionisation (MALDI) mass spectrometry, but the method suffers from poor accuracy and high detection limits. (Liagkouridis et al., 2021) found “that the TOP assay actually isn’t very efficient for breaking down SFPs, but it is good enough for identifying the length of the side-chain, which is what we used it for”.^{[1]https://chemicalwatch.com/352993/swedish-team-tests-for-side-chain-fluorinated-polymers-in-fabrics} For a quantitative approach of SFPs they combined TOP with measurement of total fluorine and applied the method to medical textiles.^{[2]Please note that this content is an early or alternative research output and has not been peer-reviewed at the time of posting.}

Another method for determination of hidden PFASs that is just recently discussed in literature is hydrolysis as pre-treatment method (“Total Hydrolyzable Precursors”, THP). Derivatives of simple PFAS precursors containing a hydrolysable link, like an ester, e.g. polymers with fluorotelomer side-chains, can be converted by hydrolysis to targeted PFASs. (Nikiforov, 2021) introduced this method and pointed out that it can be an alternative or complementary method to TOPA for assessing hidden PFASs including FTOH esters which are converted to free FTOHs. Three FTOHs were analysed in this study by GC-MS. After hydrolysis the sum of FTOH concentrations increased up to 1300 times.

Total fluorine (TF) was investigated in textiles by various methods. (Ritter et al. 2017) determined TF in papers and textiles by using Particle-induced gamma-ray emission spectroscopy (PIGE, a non-destructive surface measurement) and reported a LOD of 24-45 nmol F/cm² for textiles. In a comprehensive study by (Robel et al., 2017) TF in paper and textiles was measured by PIGE and compared to the sum of volatile, ionic PFASs and precursors determined by GC-MS, LC-MS/MS and TOPA. The sum of detected PFASs and precursors accounted for a maximum of 16% TF, indicating that most of the fluorine remains associated with the papers and textiles. (Peaslee et al., 2020) used the PIGE method to analyse TF in firefighting turnout gear. Additionally, they analysed targeted PFASs of selected samples by LC-MS and found that the concentrations of PFASs upon extraction are much lower than the TF numbers for the outer shell and the moisture barrier because the vast majority of fluorine remains as polymeric PFASs in the gear. (Tokranov et al., 2019) presented a method for determination of surficial fluorine content by X-ray photoelectron spectroscopy (XPS), that was applied to consumer products including FCM and textiles. Another approach for determination of TF content that was applied to textiles is combustion ion chromatography (CIC). (Schellenberger et al., 2019) analysed fluorine content of fibres before and after washing by CIC.

In a comprehensive study by (Wu et al., 2021) fabric, foam and composite of childrens' car seats were tested for fluorine content by PIGE and XPS and 43 targeted PFASs measured by GC-MS and LC-MS including TOP assay and UV irradiation for selected samples. Results from these treatments, as well as the much higher organic fluorine levels measured by PIGE compared to targeted analysis, suggested the presence of side-chain fluorotelomer-based polymers, which have the potential to readily degrade into PFAAs under UV light. Using XPS, they confirmed the presence of organic fluorine and CF₂ moieties.

Some more uncommon methods have also been reported in literature. (C. Wang et al., 2020) developed a method for the rapid identification of PFCAs in textiles bypassing conventional sample preparation and chromatographic separation using dielectric barrier discharge ionization (DBDI) coupled with a benchtop ion trap mass spectrometer. (Zheng et al., 2020) reported a method where fluorinated compounds separated by gas chromatography (GC) are converted to Na₂F⁺ for non-targeted detection which can be applied to leachates from textile samples. Dolan et al. presented a method for selective elemental detection of fluorine by pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). In this technique, fluorinated pyrolysates of textile fibres eluting from GC are introduced into a plasma to release F atoms that were ionized and detected by mass (Dolan et al., 2019; Dolan et al., 2021). (Q. Liu et al., 2015) employed water-soluble CdS quantum dots (QDs) to develop a simple and rapid fluorometric method for the determination of PFOA on spiked textile samples with recoveries ranging from 95% to 113%.

4.10 Waste treatment of PFAS articles & industrial waste

At the end of their lifetime all articles become waste and are subsequently treated in a waste management system. In many European countries municipal and industrial waste is still landfilled to a large extent. With time and through the influence of nature, water leaches out of the waste and is collected at the bottom of the landfill whereupon it is either treated on site or sent to a wastewater treatment plant (WWTP).

WWTP not only receive landfill leachate but also municipal and industrial wastewater. Especially the latter may have elevated PFAS concentrations if nearby industry manufactures or uses PFASs. In the WWTP typically three treatment steps are performed: a primary physical treatment step, a secondary biological treatment step and a tertiary chemical treatment step. At the end of the process the cleaned water is discharged to the surface waters, however sewage sludge is also separated and then typically incinerated. These steps are effective in removing most pollutants e.g., plastic parts, medicines and other organic compounds. However, the processes often fail to adequately remove PFASs. As such PFASs can often be found in the effluent and in the sludge in WWTP around the globe (T. L. Coggan et al., 2019). On-site treatment of landfill leachate can allow the owners to directly discharge their leachate into the sewer and typically consists of a combined biological and physical/chemical treatment.

In the water and sludge matrix, typically analysed PFASs include PFCAs and PFSAs as they are water soluble. The longer chain PFASs tend to accumulate in the sludge phase through the adsorption onto organic particles, as the longer chain length promotes intermolecular interaction. The shorter chain PFASs are thus often found in the water phase (T. Coggan et al., 2019). Other PFASs precursors such as FTOH, FOSA and FOSE and many more on the other hand have also been detected in the air around WWTP and landfills, as these molecules often exhibit higher vapour pressure than PFCAs and PFSAs (Ahrens et al., 2011).^{[1]https://www.umweltbundesamt.de/en/publikationen/investigations-on-the-presence-behavior-of}

Additionally, in many countries waste is incinerated. According to the Industrial Emissions Directive^{[2]Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions} municipal waste incinerators in Europe need to operate a temperature of least 850 °C. For hazardous waste, a temperature of at least 1,100 °C is required. This destroys most organic compounds, however PFASs have been found in the ash and leachate from waste incinerators (Liu et al., 2021).^{[3]Student thesis “Analysis of PFAS in ash from incineration facilities from Sweden”, http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1473805&dswid=592} 

4.10.1 Conclusion for monitoring and compliance measurements

For liquid and solid samples form WWTP and landfills there are already established standards available: ASTM D7979-20 can be used to analyse 21 individual PFASs in wastewater and sludge via LC-MS/MS. DIN 38407-42 analyses liquid samples via HPLC-MS/MS and can detect 11 individual PFASs. For sludge the DIN 38414-14 method can be applied which also analyses 11 individual PFASs via HPLC-MS/MS.

For different matrices from waste incineration (ash, leachate and flue gas) no standard method could be found. However, PFASs in gas can be measured via GC-MS, while ash and leachate samples can be analysed via LC-MS/MS after extraction.

4.10.2 Analytical measurements

Standards

In general, there are already established standards for the analysis of PFASs in waste water and sludge. The American Society for Testing and Materials (ASTM) provides a targeted standard test method (ASTM D7979-20)^{[1]ASTM D7979-20 “Standard Test Method for Determination of Per- and Polyfluoroalkyl Substances in Water, Sludge, Influent, Effluent, and Wastewater by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS)”} for PFASs in water and sludge using LC-MS/MS. In short, the liquid and sludge samples are spiked with surrogates and target PFASs, mixed with methanol, filtered and pH-adjusted with acetic acid. The resulting liquid samples are subsequently measured via LC-MS/MS. In total 21 target PFASs can be analysed this way including PFCAs, PFSAs as well as various 2H-acids such as n-2H-perfluoro-2-octenoic acid.

Furthermore, there are two DIN standard methods to analyse PFASs in sludge, compost and soil (DIN 38414-14)^{[2]DIN 38414-14 “German standard methods for the examination of water, waste water and sludge – Sludge and sediments (group S) – Part 14: Determination of selected polyfluorinated compounds (PFC) in sludge, compost and soil – Method using high performance liquid chromatography and mass spectrometric detection (HPLC-MS/MS) (S 14)”} and to analyse PFASs in water (DIN 38407-42)^{[3]DIN 38407-42 “Standard methods for the examination of water, waste water and sludge”}. The solid samples (sludge, compost, soil; DIN 38414-14) should not be dewatered as soluble PFASs could be lost. Instead, the samples are either freeze-dried or dried at 40 °C. The dried samples are then milled and extracted with methanol under the influence of ultrasound at 40 °C. After sedimentation, and if clear, the sample can be directly analysed via LC-MS/MS, otherwise the samples need to be further clarified. The pH of the water samples (DIN 38407-42) should lie in between 6 and 8 and should be adjusted using either sodium hydroxide or sulfuric acid. The solution is then mixed with the internal standard and a spiking solution is added. The sample is extracted via solid phase extraction (SPE) and subsequently analysed via LC-MS/MS. With both methods, 11 different PFASs can be analysed, PFCAs (C4-C10) and PFSAs (C4, 6 and 8).

Methods identified by literature search

The vast majority of published scientific articles describe a targeted analysis of PFASs for both liquid and sludge samples by using LC-MS. Air samples of volatile PFASs and fluorinated gases can be analysed with GC-MS (Scheutz et al., 2010; Y. Tian et al., 2018; B. Wang et al., 2020).

Waste water treatment plants
For example, (T. Coggan et al., 2019) were able to analyse 53 individual PFASs in an aqueous phase via LC-MS/MS. First, suitable surrogate compounds for each PFAS were determined and mixed with ultrapure methanol. After SPE using weak anion exchange cartridges the samples were analysed via LC-MS/MS. This method was tested on analytical samples as well as on WWTP influent and effluent samples with accuracies for 49 out of the 53 PFASs ranging between 70 and 127%. The remaining four PFASs ranged between 66 and 138% with regard to accuracy. In a best case scenario, accuracies of 100% should be achieved, however this is not always possible. For the majority of the PFCAs and PFSAs the accuracies lie between 95% and 105%, highlighting the precision of the method. The accuracies can be improved with suitable surrogate compounds, which are however not available for all PFASs (especially new compounds and precursors).

(Houtz et al., 2018) analysed 22 individual PFASs by applying a non-targeted analysis with quadrupole time-of-flight (QTOF). The samples were extracted with methanol, cleaned via SPE and spiked with a surrogate standard. The analysed PFASs include various PFCAs (C4, 6, 8, 10), PFSAs as well as precursors such as 6:2 FTS and FOSA. Additionally, a TOP assay was performed by heating the sampled with potassium persulfate and sodium hydroxide at 85 °C for six hours. Afterwards the solutions were neutralised with hydrochloric acid, mixed with methanol, spiked with surrogates and analysed with QTOF. This analysis was able to identify 29 individual PFASs, some of which have never been reported before.

Another method was validated by (Wille et al., 2010) who used LC-ESI-TOF-MS to analyse surface-, sea- and sewage water. The sewage samples were first filtered through glass fibre paper, mixed with ¹³C-labelled internal standards and extracted via SPE before analysis via LC-ESI-TOF-MS. The method was validated by the Flemish Environment Agency by assessing the specificity/selectivity, linearity, recovery, precision, and the limits of detection and quantification. In total 14 PFASs were analysed (4 PFSAs, 9 PFCAs and PFOSA).

(McCord et al., 2018) successfully applied LC-MS/MS to also analyse perfluoroether carboxylic acids (PFECA) and GenX-related hexafluoropropylene oxide acids (HFPOA). Environmental samples of contaminated water downstream from a fluorochemicals plant were collected and pH-adjusted with nitric acid. The samples were mixed with ¹³C labelled hexafluoropropylene oxide dimer acid and vacuum filtered through a glass filter. SPE via weak anion exchange was performed, and the samples were mixed with ammonium acetate to match the starting conditions for the following LC-MS/MS. In total four perfluoroether compounds and three PFECAs were analysed. The authors state that for the PFECAs no analytical standards were available, so direct infusion of extracts from a river sample were prepared. The method was tested over multiple weeks by replicating random samples. The difference in results were below 10% demonstrating long term method stability and the ability to accurately analyse more complex PFASs.

To analyse more volatile PFASs such as fluorotelomer alcohols (FTOH) and N-alkylated perfluorooctane sulfonamides and sulfonamidoethanols (FOSA/FOSE) (Portolés et al., 2015) successfully applied atmospheric pressure chemical ionization (APCI) combined with gas chromatography with triple quadrupole time-of-flight mass analyser (GC-TOF-MS/MS). Samples were taken from a river in Spain, which receives industrial wastewater and from a local WWTP. The samples were extracted via SPE, the cartridges washed with a methanol/water solution and the extract evaporated under a nitrogen stream. The sample was then injected into the GC-TOF-MS/MS system. In total four different FTOHs and two FOSA and FOSE were analysed using this method. The fragments of each compound made it possible to distinguish them from one another and the measured concentrations in the environmental samples ranged between 1-100 pg/L demonstrating a low LOD for this method.

Landfills
Analysing landfill leachate is often performed in the same way as analysing waste water and sewage sludge by applying LC-MS.

For example, (Knutsen et al., 2019) sampled ten different landfills in Norway for their leachate and sediment from sedimentation ponds and analysed 28 individual PFASs (PFCAs, PFSAs, FTSAs, FTOHs, FOSAs and FOSEs). The sediment was centrifuged in methanol and extracted SPE whereas the leachate was analysed by SPE-methanol elutriation. Both samples were then analysed via UPLC-MS/MS.

A total of 70 individual PFASs were analysed by (Allred et al., 2014) using orthogonal zirconium diol/LC-MS/MS. Samples were taken from various landfills in the USA. The samples were extracted via liquid-liquid extraction (LLE) by first centrifuging, mixing with isotopically labelled standards, neutralising to pH 7-8, extraction with 10% trifluoroethanol in ethyl acetate and finally methanol was added before injecting into an HPLC. The HPLC was equipped with two Zorbax zirconium modified diol (Zr-diol) guard columns placed in series with a Zorbax Eclipse PlusC18 column. The eluent was then analysed in a mass spectrometer. The analysed PFASs included PFCAs, PFSAs, FTCAs, FTSAs to diPAPs, PFPIAs and FTMAPs demonstrating that this method can be applied to complex landfill leachate samples with good results.

LC-MS/MS was also successfully used by (Benskin et al., 2012) to characterise perfluoroalkyl carboxylate (PFCAs), sulfonate (PFSAs), and sulfonamide (FOSAs) isomers in landfill leachate samples from Canadian landfills. The unfiltered samples were extracted via SPE and analysed by HPLC-MS/MS. The PFASs were quantified by creating a six-point calibration curve from bought isomer containing standards. The authors successfully identify the different isomers of the target PFASd in a short amount of time, demonstrating that HPLC-MS/MS can also distinguish between isomers.

Incineration
Instead of landfilling, waste can also be incinerated leading to solid (ash), liquid (leachate, flue gas cleaning water) and gaseous (flue gas) matrices which can possible contain PFASs.

(Liu et al., 2021) analysed fly and bottom ash as well as leachate from three waste incineration plants in China. The leachate samples were taken from the waste storage area in the wet and dry months for better representativity. The leachate samples were first centrifuged to remove large particles, extracted using SPE and mixed with a M4PFOS (the first 4 carbon atoms are ¹³C carbon atoms) standard. The fly and bottom ash samples were lyophilised and homogenised in a solvent cleaned pestle and mortar. After this process a sodium hydroxide solution was added and after 30 minutes methanol was added followed by an ultrasonic bath. The sample was neutralised using hydrochloric acid and centrifuged again. All three samples were analysed via UHPLC-MS for a total of 22 individual PFASs (PFCAs, PFSAs, PFPAs and diPAPs). Matrix recovery tests were conducted in duplicate, and the matrix recoveries ranged from 56 to 107% for leachate, 25–91% for fly ash, and 32–129% for bottom ash.

In a student thesis by Wohlin (2020),^{[1]Student thesis “Analysis of PFAS in ash from incineration facilities from Sweden”, http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1473805&dswid=592} incineration ash from multiple waste incinerators in Sweden was analysed. Three extraction methods were evaluated over the course of the project: 1) Soxhlet extraction using methanol, 2) liquid-solid extraction with a 50:50 mixture of acetone and hexane, 3) liquid-solid extraction using methanol. The samples were analysed using UPLC-MS/MS, as well as for EOF using combustion ion chromatography (CIC). In total 24 individual PFASs were analysed (PFCAs, PFSAs, FTSAs and PFOSA). The authors conclude that the liquid-solid extraction using methanol provided the best results for the individual PFAS, whereas the concentrations of the extracts were too low for an accurate EOF measurement.

Lastly (C. H. Wang et al., 2021) analysed the flue gas of a semiconductor facility after the thermal gas scrubbing for F-gas emissions. By using a thermal desorption apparatus coupled with GC-MS the authors were able to detect C₄F₈ in the flue gas, which was verified by injecting and measuring a gas standard of the said compound. While the analysed matrix did not stem from waste incineration the result demonstrates that F-gases, which are also PFASs, can be accurately detected in flue gas via GC-MS.

4.11 Lubricants

According to (Glüge et al., 2020) the PFAS used in lubricants and greases are predominantly fluoropolymers and PFPEs. PFPAs can be used as base oils and fluorinated additives (most commonly (micropowder) PTFE) can be added to e.g. reduce friction and ware (Ebnesajjad & Morgan, 2019). These fluorinated lubricants are used in almost any sector (food, aircraft/aerospace, automotive, trains, paper, plastics). The EU is currently in the process of implementing a restriction on the intentional use of microplastics with the combined opinion of the RAC and SEAC presented to the Commission in February 2021. Based on this restriction proposal some applications of PTFE micropowders, that are believed to exist in the 0.25 - 500µm (0.5mm) range, fall well within the scope of the microplastic restriction.

4.11.1 Conclusion for monitoring and compliance measurements

Based on previous studies, analysis of lubricants may be done by characterization of fluoropolymers and PFPEs in the surface layer, regarding composition, molecular weight and layer thickness. The studies focussing on the detection of monomeric PFASs show that detection is feasible using similar methods as for other matrices.

4.11.2 Analytical measurements

Methods identified by literature search

In literature, lubricants are mostly characterized as surface measurements using Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). This is an already well-established technique with a first publication from 1991 and still in use in publications from 2018 and 2020. (Lorenz et al., 1991; Tani et al., 2018; Tani et al., 2020; Zhang et al., 2004; Zhu et al., 2002). This technique can be used directly on the material without requirement of a preliminary sample preparation step. The technique is, however, not used for absolute quantification. The parameters that are mostly determined by TOF-SIMS are: the type of polymer used, the molecular weight and the layer thickness. (Zhu et al., 2002) used the technique also to follow the kinetics of the etching time, looking at backbone fragments CF2O and C2F4O.

Chain composition, end groups and molecular weight can also be determined using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) (Karis et al., 2002).

An alternative surface analysis technique used is Laser Desorption Ionization Time-of-Flight. This method requires the addition of a NaTFA solution sprayed on the disk surface before analysis. With this technique the type of polymers can be determined but not the quantity (Kudo et al., 2011).

To measure the PFASs content, more traditional targeted methods are used. The samples are extracted using ultrasound extraction followed by solid phase extraction (SPE) clean up. Targeted LC-MS/MS is performed on a QqQ instrument(Y. Zhang et al., 2018).  These measurements show for example that oxidation of the lubricants leads to a seriously increased level of PFAAs (range of 196–8300 ng/g (1840 ng/g mean) after vs. 5.96–344 ng/g (71.6 ng/g) prior to oxidation) (H. K. Zhu & K. Kannan, 2020). With regards to quality these studies fit within the validation parameters of other studies regarding linearity, recovery, repeatability and LOD (0.01-1 ng/L).

4.12 Oil, Gas, and mining

The Norwegian Environment Agency has recently published a report called: “PFAS in mining and petroleum industry – use, emissions and alternatives”. This report gives a detailed description of the use of PFASs (monomers and fluoropolymers) in the sector. The report covers the function of the PFAS, the typical applications, the PFAS levels, emissions and exposures and possible alternatives and implications of a PFASs restriction.

No application of non-polymeric PFASs was identified in mining, while in the oil and gas sector PFASs are mostly used as an (anti)foaming agent or surfactant, but also as a tracer. Fluorinated polymeric material is widely used within oil and gas in diverse equipment, and it is likely that such materials are also used for different purposes in mining. The total fluoropolymer sales for these industries are 3500–7500 tonnes per year which represents 5% of the total sales.

Life cycle analysis for these PFASs shows 4 major stages: production, formulation, use and waste. Since the use is mostly outdoor, direct release into the environment can be expected. Release scenarios are described in detail in the report.

PFASs used in gas tracers are all volatile. Examples of these compounds are: perfluoromethylcyclohexane PMCH, perfluoro-1,2-dimethylcyclohexane PDCH, perfluoromethylcyclopentane PMCP, perfluorodimethyl cyclobutene PDMCB and 1,2-PDMCH, 1,3-PDMCH. Also, SF₆ is used as a gas tracer.

4.12.1 Conclusion for monitoring and compliance measurements

All publications that were found focus on the detection of gas tracers, which is an established technique in the oil- and gas-industry. PFASs analysis directly in oil, gas or other mining samples (for example as foaming agent) could not be found. It can be assumed that these matrices might imply some difficulties, since they are very hydrophobic samples, differing significantly from well-established measurements related to more aqueous matrices.

4.12.2 Analytical measurements

Methods identified by literature search

The literature available on analytical methods only focusses on the gas tracers analysis. Other related analyses are all focused on environmental analysis and are covered in chapter 4.18.1.

Sampling of gas tracers is performed by using trapping tubes or solid phase microextraction (SPME) under dynamic conditions. Analytical measurements are performed using mostly GC-ECD or GC-MS with a thermal desorption autosampler coupled to the GC. GC-Columns used vary from Carbopack columns to Al₂O₃ PLOT columns or molecular sieve columns. Detection levels for these trace gases are in the fL/L range (0.01 ppt) (Galdiga & Greibrokk, 1997, 2000; Keiter et al., 2016; Nazzari et al., 2013).

4.13 Construction products

There are two main categories of PFAS uses within construction: coatings and products (Glüge et al., 2020). “Coatings” cover PFAS containing mixtures applied to a pre-existing article while in the category “products” PFASs used within an article. More than 30 different PFASs have been identified as used in articles in this sector, both polymeric and non-polymeric. Some uses like e.g. anti- graffiti coating can contain non-polymeric PFASs that become polymeric PFASs (side-chain polymers) when applied. For coatings, more than 50 different PFASs were identified. In addition, PFASs may be used as adhesives and sealants as well as processing aids. In paint fluorinated surfactants can function as an emulsifier for the binder, as dispersant for the pigment, and as wetting agent. Additionally, they can also be used to impart oil- and water repellency to the paint or coating. However, in the dried film, the fluorinated surfactant acts as an external plasticizer, imparting softness and flexibility. Large amounts of fluoropolymers (more than 3000 t between 2000 and 2017) have been used in coatings and paints in the Nordic countries between 2000 and 2017 (Glüge et al., 2020).

4.13.1 Conclusion for monitoring and compliance measurements

For the construction products a well-established standard can be used as a basis for the measurement of PFAS: Method CEN/TS 15968 is available for determination of PFOS in paper and board FCM by LC-qMS or LC-MS/MS. This method was further adapted by (Janousek et al., 2019) who successfully measured PFASs in 51 different building materials. Paint can also be extracted, similar to other consumer products as described in the consumer product chapter.

4.13.2 Analytical measurements

Methods identified by literature search

Only methods for targeted analysis of PFASs are available in literature for the construction products, no methods for the non-targeted or total fluorine contents were found.

The method used by (Janousek et al., 2019) is based on CEN/TS 15968^{[1]CEN/TS 15968 - “Determination of extractable perfluorooctanesulphonate (PFOS) in coated and impregnated solid articles, liquids and fire fighting foams - Method for sampling, extraction and analysis by LC-qMS or LC-tandem/MS” The method is applicable for a concentration range of PFOS in the extract solution of 0.5 µg/L to 50 µg/L. In short, the analytes are extracted with methanol and determined by LC-MS/MS.} with some small adaptations with regards to choose of extraction solvent and additional clean-up with solid phase extraction (SPE). Depending on the sample type, either extraction via liquid–solid extraction (LSE) or SPE is performed. Quantification is done by UPLC-MS/MS. The PFASs content of 51 building material and fabric samples were investigated in order to estimate their possible contribution to environmental PFAS concentrations. In total, PFASs were detected in 39% of investigated building material samples. Perfluorobutanoic acid (PFBA) was the most frequently detected PFAA in building material samples (26%). The data for building materials indicated a predominant use of short-chain PFAAs. Within the building materials, the highest diversity of PFAAs and the highest sum of PFAS concentrations was observed in coatings.

In a study by (Bečanová et al., 2016) a wide range of building materials, consumer products, car interior materials and waste was investigated. The samples were crushed, cut chopped or grinded into small pieces which were extracted with methanol using a Soxhlet extraction. The extract was concentrated and directly injected to the LC-MS/MS. PFAAs were detected in composite wood building materials. The predominant PFAAs detected were C5-C8 PFCAs.

Some related studies (Dolman & Pelzing, 2011; X. Trier et al., 2011) focused initially on matrices like food packaging materials (popcorn bags) and expanded subsequently the method to also cover construction products (e.g. PTFE sealant tape or waterborne coatings containing PFASs. The sample preparations are quite similar among these methods (SPE, LSE, ultrasonication), and the measurements are all done by the generic UPLC-MS/MS method. In a study of the effectiveness of industrial hygiene controls in processes involving PFOA products and intermediates by (Botelho et al., 2009) a wipe test method was developed and validated for quantification of PFOA on different surfaces. The method was well validated and acceptable results were obtained for non-porous surfaces.

Paint has been scarcely researched but (Okamura et al., 2012) has used methanol extraction in a standardized laboratory rotating-cylinder method (ISO 207: Paints and varnishes – Determination of release rate of biocides from antifouling paints – Part 1: General method for extraction of biocides. ISO 15181-1: (2007) (E), 9pp.). The test cylinders with artificial seawater were painted, and several ecological tests and well as chemical analysis for organic micro pollutants such as PFASs were performed.  No PFASs were detected above the level of blank cylinders in this study.

In one publication the authors pointed out that for the development of compound-specific methods it is important to understand the stability of PFASs in solvents used for analytical testing, first (Zhang et al., 2021). They measured stability of 21 PFASs (18 PFEAs, e.g. GenX, HFPO−DA) in various organic solvents. In this study all selected PFASs were stable in deionized water, methanol, and IPA at room temperature over a period 30, however, nine of the selected PFEAs degraded in the polar aprotic solvents ACN, acetone, and DMSO which can lead to an underestimation of concentrations in analytical testing.

4.14 Metal plating

Fluorinated surfactants are used in chrome plating baths to prevent the evaporation of hexavalent chromium(VI) vapour and aerosols. According to (Glüge et al., 2020) PFASs that have been used in chrome plating are PFSAs, fluorotelomers, perfluoroalkane sulfonyl fluoride (PASF) derivatives, perfluoroalkane carbonyl fluoride (PACF) derivatives, perfluoropolyethers (PFPE) or other fluoropolymers. In some countries PFOS and related substances are still in use (Glüge et al., 2020). The use of PFOS is allowed in the EU “for non-decorative hard chrome plating in closed loop systems”.^{[1]POP Regulation on PFOS, its salts and PFOSF in Annex B to the Stockholm Convention http://chm.pops.int/Implementation/IndustrialPOPs/PFOS/Overview/tabid/5221/Default.aspx} 

4.14.1 Conclusion for monitoring and compliance measurements

There is currently no standard method available for determination of PFASs in mist suppressing agents for metal plating (especially chrome plating). However, targeted analysis of a subset of PFASs can be done by GC-MS and LC-MS or MS/MS (depending on the PFAS type) according to published methods.

4.14.2 Analytical measurements

Established methods used by agencies

There is a study report from 2020 by the Michigan Department of Environment, Great Lakes, and Energy on “Targeted and Non-targeted Analysis of PFAS in Fume Suppressant Products at Chrome Plating Facilities“.^{[1]https://www.michigan.gov/documents/egle/wrd-ep-pfas-chrome-plating_693686_7.pdf} They analysed 25 targeted PFASs (PFSAs, PFCAs, FTSs, GenX, N‐EtFOSAA, N‐MeFOSAA) in fume suppressants and facility effluent by UPLC-MS. In this study only 6:2 fluorotelomer sulfonates (FTS) were found in fume suppressant samples.

Methods identified by literature search

Only one publication was found in which PFASs were analysed in suppressor agents for the chromium industry next to other liquid commercial products (Favreau et al., 2017). They searched for 41 targeted PFASs (e.g., PFCAs, PFSAs, PFPAs, FOSA, FTSAs, FTOHs) by GC-MS/MS and LC-MS/MS. In one suppressor agent they found very high concentrations of PFOS, and in another sample high concentrations of 6:2 FTS.

In some peer-reviewed articles the authors determined PFAS concentrations in wastewater (effluent and influent) from the chrome plating industry (Jiawei et al., 2019; Wang et al., 2013). These publications do not study the fume suppressants itself and therefore will not be discussed further in this chapter. The waste water is either treated on site or routed to a WWTP. The most common analysis method for PFASs in waste water is LC-MS/MS (see chapter 4.10), which was also applied by both authors.

4.15 Production of PFAS, including polymers

In the chemical industry PFASs have been extensively used in the production of plastic and rubber and other chemicals (e.g., chlorine, sodium hydroxide, solvents).

In the production of plastic and rubber they have been used as mould release agents, foam blowing agents, in the etching of plastics, as antiblocking agents for rubber, and as curatives for fluoropolymer formulations (Glüge et al., 2020). PFASs have been used as processing aids for fluoropolymers and non-fluorinated polymers. Fluoropolymer-based processing aids have been mainly used in the production of linear low-density polyethylene blown film, but they are also suitable for high density polyethylene, polyvinyl chloride, polystyrene, polyamide, polyolefins, and other standard and engineering polymers in various applications. In recent years, perfluorocarbons and hydrofluorocarbons have been used as foam blowing agents instead of chlorofluorocarbons. For many plastic types (thermoplastics, polypropylene, epoxy resins, and polyurethane elastomer foams) fluorinated surfactants have been used as (mould) release reagents. For example, perfluorobutane sulfonyl fluoride (PBSF)-derivatives (or other various C4-perfluoroalkyl compounds) are currently used in rubber moulding. In the production of fluoropolymers, fluorinated surfactants increase the rate of polymerization and improve the physical properties of the polymer. A broad range of PFASs have been used as surfactants for fluoropolymers, especially per- and polyfluoroalkylether carboxylic acids.

Also, in the production of other chemicals, PFASs have been used for several purposes. For example, PTFE has been used as technical equipment in inert reaction or storage vessels due to its outstanding chemical resistance or embedded in membranes in the production of chlorine and sodium hydroxide. Another example are hydrofluoroethers such as the commercial mixtures HFE-7100 and HFE-7200 that have been marketed as specialty solvents, dispersion media and reaction media.

Although several types of PFASs are used in the production, in this chapter the focus is on the production of PFASs itself (including fluoropolymers).

4.15.1 Conclusion for monitoring and compliance measurements

A low number of papers was found that deal directly with the detection of PFASs in the manufacturing process itself or in produced polymers. When a link is made towards more downstream matrices (e.g. consumer products, AFFF, and construction products), it is reasonable to assume that similar extraction and detection techniques can be used to analyse directly in the produced materials. Moreover, in some cases the analytical methods used for environmental monitoring of PFASs may be used to investigate samples from nearby manufacturing sites as well, see Section for Environmental samples 4.18.1. More recent literature starts to use fingerprinting techniques to link observed contamination in the environment to specific production sites/ products.

4.15.2 Analytical measurements

Methods identified by literature search

In literature, only limited publications can be found that deal directly with analytical methods relevant for the production of PFASs. The great majority of the publications focus on waste, or environmental release of PFASs.

(Jiang et al., 2015) use LC-MS to study PFOS and PFOA isomer patterns. PFOS was found to be 76.7–80.6% pure with the major impurity being PFOA, which contributes more than 10%. Other impurities include PFHxS, PFHxA and PFHpA. The percentage of linear PFOS (n-PFOS) in PFOS obtained from 3 different manufacturers was 66.2–71.9%, The purity of PFOA from 5 different manufacturers was relatively high (94.0–95.8%), and the major impurity was PFOS (2.06–3.09%). The percentage of n-PFOA in the five PFOA products was 76.4–77.9%.

(Romack et al., 2007) describe that Electrospray ionization time-of-flight mass spectrometry (ESI-ToF-MS) has been employed for the characterization of molecular weight, molecular weight distribution and end groups for bromine-terminated perfluoroalkyl acrylate oligomers prepared using atom transfer radical polymerization and compared these results successfully with GPC-MALS and ¹H NMR spectroscopy.

Other publications study the extraction of PFASs from different matrices using different absorbents. (Deng et al., 2013; Larsen et al., 2006; Yan et al., 2013). (Larsen et al., 2006) use pressurized solvent extraction (PSE) and LC-MS/MS to quantify the perfluorooctanoate from PTFE fluoropolymers. (Yan et al., 2013) use mesoporous carbon nitride to extract PFOS and (Deng et al., 2013) use aminated rice husk prepared by atom transfer radical polymerization for PFOA, PFBA and PFOS extraction.

A number of publications look at environmental samples in such a way that the detected PFASs can be related to production processes and plants. (Xie et al., 2020) determined the TFA amount in air, soil and water in the surroundings of a plant with reported levels of 250–3000 ng/L water, <0,1–2,6 ng/g in soil and 1000–7000 pg/m³ in air. (Jin et al., 2015; Shi et al., 2015) looked at water and soil in the vicinity of manufacturing plants using LC-MS/MS. They performed both targeted PFASs analyses and looked at isomer profiles. PFAS concentrations ranging from 36.5 to 496 000 ng/L in water and from 0.333 to 4100 mg/kg dw in sediment were found, and PFOA was the main homologue. (Li et al., 2020) used LC-MS/MS to quantify PFASs in river water. The total concentrations of targeted PFASs ranged from 1.74 to 172 ng/L, with PFOA as the dominant compound (15.2%). A software program Unmix was introduced to identify the sources of PFASs in the surface water, and the results indicated that fire-fighting foam/fluoropolymer processing aids (36.6%) contributed most. Tracing back the manufacturing sources of PFOA by fingerprinting, Electrochemical fluorination (ECF) was found to be the major PFOA manufacturing source with considerable contribution by telomerization.

4.16 Transportation, Automotive, Aircraft, Space and Ships

Products and articles containing PFASs used in the transportation sector are very diverse. For example, PFASs are used in construction (see chapter 4.13), sealing applications, combustion engine systems, lubricants (see chapter 4.11), hydraulic fluids, electrical engineering (see chapter 4.17), coatings and finishing’s, interiors, health protection equipment or other uses related to transportation. Depending on use and material, different PFASs are applied. For many applications (e.g. coatings, sealings, construction) fluoropolymers like PTFE, ETFE, perfluoroalkoxy alkane (PFA), or fluoroethylene vinyl ether (FEVE) are used. Heating, ventilation, air conditioning and refrigeration (HVACR)-systems can contain F-gases (see chapter 4.2).

At present, there are two major PFAS applications in modern lithium-ion batteries: PVDF (polyvinylidenefluoride) is used as a binder for coating the cathode with metal oxides and fluoroorganic additives in electrolytes for improving the lifetime of battery cells. PFASs have many different applications in fuel cells, power electronics, technical textiles and seals and hoses.

4.16.1 Conclusion for monitoring and compliance measurements

The category “Transportation, Automotive, Aircraft, Space and Ships” is relatively broad with diverse applications of PFASs, including fluoropolymers, and has overlaps with many other categories concerning applications and PFASs used in similar matrices. In this project, no relevant information has been found that focuses on the PFASs analysis in this particular category. However, based on the overlaps with other categories with applications of PFASs in similar matrices, it can be assumed that PFASs within this category are covered by analytical techniques described in their respective chapters in this report.

4.16.2 Analytical measurements

No publications were found that are directly related to analysis to PFASs in the transportation sector. Related publications are either dealing with lubricants (chapter 4.11), waste (chapter 4.10), consumer products (chapter 4.5) and F-gas refrigerants (chapter 4.2) used in car parts like e.g. textiles (chapter 4.9) or air conditioning. These applications are discussed in separate chapters and are not further discussed here.

4.17 Electric and electronic equipment including semiconductors

PFASs have been extensively used in the electronics industry due to their water-repellency, low surface-tension and high dielectric and breakdown strength (Glüge et al., 2020). PFASs have been used in electronic devices themselves (e.g., in flat panel displays or liquid crystal displays), for the testing of electronic devices and equipment, as heat transfer fluids/cooling agents, in cleaning solutions, to deposit lubricants and to etch piezoelectric ceramic filters. According to (Glüge et al., 2020) PFASs used in electronics represent a significant part of the total PFAS consumption. Functional fluids in “electrical equipment, appliance, and component manufacturing" were identified as large contributor to used and exported amounts of PFASs.

According to (Glüge et al., 2020) a broad variety of PFASs have been used in the electronic industry, the hydrofluorocarbon pentafluoroethane (HFC-125) was widely employed as a functional fluid. HFC-125 is not only of concern due to its high persistence but also because it has a global warming potential that is 3500 times that of carbon dioxide. Other PFASs that were used are e.g., perfluoroalkyl ethers, perfluorocarbons, fluoropolymers, and FTSAs amongst others.  

Also, in the energy sectors several PFASs (especially fluoropolymers) have been used (e.g. in photovoltaic cells, wind mills, coal based power plants) (Glüge et al., 2020).

4.17.1 Conclusion for monitoring and compliance measurements

There is no standard method for determination of PFASs in electronic equipment available. In literature, targeted PFASs in electronic equipment were analysed by LC-MS and/or GC-MS. We assume that some methods which were applied for other matrices can also be adopted for electric and electronic equipment. For example, HFC-125, which has been widely used as a functional fluid in the electronic industry, is measured by Medusa GC-MS in the Advanced Global Gases Experiment (AGAGE) (see section on F-Gases 4.2).

4.17.2 Analytical measurements

Methods identified by literature search

Two peer-reviewed articles describe the analysis of targeted PFASs by GC-MS and/or LC-MS in electronic equipment besides other consumer products. No publications were found that deal with analysis of PFASs in the energy sector (e.g. in photovoltaic cells, wind mills, coal based power plants).

In a study by (Bečanová et al., 2016) 18 samples referred as electrical & electronic equipment were analysed for 15 targeted PFASs (PFCAs, PFSAs) among other consumer products and building material. More precisely, the electrical and electronic products included a switch, coffee maker, vacuum cleaner, iron, fridge insulation (plastic, rubber, foam), iron, TV, screens, and keyboards. Targeted PFASs were analysed in the methanol extracts of the products by LC-MS/MS. Method quantitation limits (MQLs) were between 0.02–0.23 µg/kg. In another study by (Herzke et al., 2012) targeted PFASs in 6 different product groups were investigated. The group “electronics” included three printed circuit boards. Samples were extracted with methanol for ionic PFASs (PFCAs, PFSAs, FTSs, PFOSA) and ethyl acetate for FTOHs. Ionic PFASs were analysed by LC- Q)ToF-MS and FTOHs by GC-MS. Very low PFAS levels were detected in the printed circuit boards: Trace amounts of PFOS in all three printed circuit boards, with two of the three printed circuit boards containing traces of 6:2 FTS as well.

In other studies, PFASs in electronic equipment was not measured, but the impact of electronic industry on the environment. For example, (Jacob et al., 2021) determined PFASs (PFCAs, PFSAs, FTSs, FOSA, MeFOSAA, N-EtFOSAA, GenX) in wastewater from electronics manufacturing facilities using an untargeted high-resolution LC-MS approach. Sum concentrations of target and non-target PFASs in the diluted discharge samples from these facilities ranged from 1490 to 78700 ng/L.

4.18 Human and environmental samples for monitoring

In the previous chapters the focus was given to analytical methods for analysing the content of PFAS components in defined matrices in specific use categories. Such methods are needed to verify the content of PFASs in those matrices and check for compliance with a potential restriction on PFAS. The following chapter supplements the overall picture with analytical methods for environmental and human samples for monitoring.

The high persistence of PFASs in the environment is one of the main concerns that led to policy actions at EU level. In general, PFASs can enter the environment via various direct and indirect routes. This covers potential release during production or industrial use but also release of PFASs during use of consumer products and releases during the waste phase. Especially their mobility in water and air lead to contamination of ground and drinking water. In addition, F-Gases, that are used in a broad range of industrial applications contribute with degradation products like trifluoroacetic acid (TFA) to a contamination of the environment with PFASs.

In order to assess the exposure to human beings Human Biomonitoring can be utilised. The sampling and measurement of different invasive and non-invasive human matrices (like blood, urine, hair, etc.) reveals an indication of the body burden of EU citizens. Having available (human) biomonitoring data on a European level will enable policy makers to evaluate the effectiveness of the legislation over the next decades, so that such data can complement the overall efforts related to the PFASs restriction.

4.18.1 Environmental samples

For environmental samples several different matrices are considered in the follow|ing. In particular, different types of water samples as well as abiotic environmental solid matrices (dust, soil, sludge and sediments) are addressed. Air samples are considered separately as special analytical sampling methods are necessary.

Drinking water, ground water and surface water

Several norms, standards or harmonized methods are available for the analysis of water samples, which are commonly used and reported in literature.

• ISO 21675:2019: Water quality — Determination of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in water — Method using solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS); The scope of the method is drinking, natural and waste waters. Analytes determined are C4-C18-PFCAs, C4-C10 PFSAs, FOSA, MeFOSA, EtFOSA, FOSAA, MeFOSAA, EtFOSAA, 6:2 FTS, 8:2 FTS, 9Cl-PF3ONS, 8:2 FTUCA, 8:2 diPAP, HFPO-DA (GenX), ADONA (total of 30 PFAS). Extraction is carried out by SPE on a copolymer-based weak anion exchanger (e.g. Oasis WAX); PFAS are eluted with methanol and alkaline methanol (0.1% NH₃). The extract is injected into an LC-MS/MS system; typically, a C18 column is used with a water/methanol/ammonium acetate mobile phase gradient. Quantification is done by the internal standard method (isotope dilution).
• ISO 25101:2009: Water quality - Determination of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) - Method for unfiltered samples using solid phase extraction and liquid chromatography/mass spectrometry; HPLC-MS/MS; other isomers may be reported separately as non-linear isomers and qualified as such. The method is applicable to a concentration range of 2.0 ng/l to 10 000 ng/l for PFOS and 10 ng/l to 10 000 ng/l for PFOA. Depending on the matrix, the method may also be applicable to higher concentrations ranging from 100 ng/l to 200 000 ng/l after suitable dilution of the sample or reduction in sample size.
• EPA METHOD 533 (12/2019): Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry.
• EPA METHOD 537.1 (12/2018): Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS); scope: drinking water; analytes determined: C4-C14 PFCAs, C4-C8 PFSAs, MeFOSAA, EtFOSAA, 11Cl-PF3OUdNS, 9Cl-PF3ONS, 8:2 FTUCA, 8:2 diPAP, HFPO-DA (GenX), ADONA (total of 18 PFAS). Extraction is carried out by SPE on a styrene-divinyl benzene sorbent phase; PFAS are eluted with methanol. The extract is injected into an LC-MS/MS system, equipped with a C18 column. A water/methanol/ammonium acetate mobile phase gradient is used. Quantification is done by the internal standard method. Limits of quantification range from 0.53–6.3 ng/l.
• EPA Draft method 1633: Analysis of PFASs in Aqueous, Solid, Biosolids and Tissue samples by LC-MS/MS.
• US EPA OTM45: Measurement of Selected Per- and Polyfluorinated Alkyl Substances from Stationary Sources in air using sampling Train with XAD resin and impingers and liquid chromatography/mass spectrometry. Analytes determined: PFOS, PFOA, EtFOSAA, MeFOSAA, PFBS, PFDA, PFDoA, PFHpA, PFHxS, PFHxA, PFNA, PFTeDA, PFTrDA, PFUnDA, HFPO-DA (GenX), PFBA, PFPeA, PFDS, PFHpS, PFPeS, FOSA, 4:2 FTS, 6:2 FTS, 8:2 FTS, 10:2 FTS, 8:2 FTUCA or FOUEA, MeFOSA, EtFOSA, PFHxDA, PFODA, 9Cl-PF3ONS, ADONA, PFNS, PFecHS, 3:3 FTCA, 5:3 FTCA, 6:2 FTCA or 6:2 FHEA, 7:3 FTCA or FHpPA, 6:2 FHUEA, PFEESA, NFDHA, PFMPA, PFMBA, 11Cl-PF3OUdS, N-MeFOSE, N-EtFOSE, PFDoS, 8:2 FTA or FOEA, 10:2 FDEA.
• EPA method 8327:2021: Validated Test Method 8327: Per- and Polyfluoroalkyl Substances (PFAS) Using External Standard Calibration and Multiple Reaction Monitoring (MRM) Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS); the scope of the method is groundwater, surface water and wastewater. The method was revised and re-published in July 2021. The 24 PFAS that have been evaluated with this method are: PFBS, PFPeS, PFHxS, PFHpS, PFOS, PFNS, PFDS, 4:2 FTS, 6:2 FTS, 8:2 FTS, PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFTeDA,  N-EtFOSAA, N-MeFOSAA and PFOSA. Water samples are diluted 1:1 with methanol, filtered, and acetic acid (0.1% by volume) is added to adjust pH to ~3 – 4. Acetic acid is added primarily because it improved sensitivity for some target analytes. Samples are then analysed by LC-MS/MS using external standard calibration.
• ASTM 7979-19:2019 (11/2019): Standard Test Method for Determination of Per- and Polyfluoroalkyl Substances in Water, Sludge, Influent, Effluent, and Wastewater by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS); the scope of the method is non-drinking water (surface water, influent and effluent). Analytes determined are C4-C14 PFCAs, C4-C8 PFSAs, PFECHS; 6:2 FTA, 8:2 FTA, 10:2 FTA, 6:2 FTUA and 8:2 FTUA (total of 21 PFAS). The analysis is done by direct injection (after 1:1 dilution with methanol) into an LC-MS/MS system. Quantification is done by the external or internal standard method. For most compounds a limit of quantification <10 ng/l applies.
• DIN 38407-42:2011-03: “German standard methods for the examination of water, wastewater and sludge – Jointly determinable substances (group F) – Part 42: Determination of selected polyfluorinated compounds (PFC) in water – Method using high performance liquid chromatography and mass spectrometric detection (HPLC-MS/MS) after solid-liquid extraction (F 42)- analytes covered: PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFBS, PFHxS, PFOS; the samples are analysed in the unfiltered state. The pH value of the sample should lie in the range between pH 6 and pH 8 and shall be adjusted with sodium hydroxide solution or sulfuric acid, if necessary. A LC-MS/MS method is used.

Mostly based on the EPA methods, instrument manufacturers are constantly validating and improving parts of the protocol (for example extraction, ionization, detection). A list of available application notes detailing the protocols and validations can be found in the attached Excel sheet. Mostly these application notes focus on water samples, but also soil, FCM and serum are being used as matrices. The methods mostly use LC-QqQ, but in some non-targeted methods high resolution MS are used and the corresponding data analysis is described.

Targeted methods focus on the use of LC-MS/MS. A recent review of the determination of PFASs in the environment is available by (Nakayama et al., 2019). The principle of the methods has already been applied over decades. Most studies used LC-MS/MS, operated in multiple reaction monitoring mode (MRM) (Borrull et al., 2020), although some studies used HRMS such as Orbitrap- or time-of-flight (TOF)-MS for quantitative and qualitative analyses (Concha-Graña et al., 2018; Tröger et al., 2018). MS was generally operated in ESI-negative mode. For neutral PFASs such as FASAs, FASEs and FTOHs, atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) have been tested (Ayala-Cabrera et al., 2018).

A special focus in the search was given to TFA as a key environmental substance. However, the literature search revealed only very limited information on specific methods. (Xie et al., 2020) investigated water, air and soil samples for TFA, therefore different pre-treatment steps were applied. The analysis was done by LC-MS.  used a LC-MS/MS method with an SPE extraction to investigate several PFAS compounds including TFA in water samples. Two stationary phases for LC (Obelisc N and Kinetex C18) and two materials with weak anion-exchange properties for SPE (Strata X-AW and Oasis WAX) were investigated. Robust separation and retention were achieved with the reversed phase column and an acidic eluent. (Chen et al., 2019) conducted a nationwide survey on PFASs in precipitation across mainland China. Samples were analysed with an LC-MS/MS after a separation step according to the chain lengths. TFA displayed the highest concentrations which were particularly elevated in coastal cities.  

The workshop report from the workshop on PFASs monitoring organized by the European Commission in 2020^{[1]Umweltbundesamt-Final-Workshop-Report-(Workshop-and-workshop-report-on-PFAS-monitoring)-vanKeer-Hohenblum-B-en-et-al-Conference-Center-Albert-Borschette-Brussels-13-14-January-2020.pdf
(kwrwater.nl)} addresses in addition to the pure analytical methods the importance and possibilities related to extraction and sampling techniques for analysis of PFASs in the environment. 

In particular, when very low detection limits for PFASs are necessary, a concentration step needs to be considered in order to achieve the detection limits. Solid phase extraction (SPE) can effectively concentrate PFASs from a water sample by capturing the PFASs which are then eluted from the SPE (Sanan & Magnuson, 2020) (Brumovsky et al., 2018). Nowadays, SPE methods use anionic exchange materials, conditioned at pH 9, subsequently washed at pH 3 and eluted with a mixture of an organic solvent (methanol or acetonitrile) and ammonia solution. Non-ionic Oasis HLB SPE-material can be used as stationary phase as well. Depending on the chain lengths of interest, parameters can be adjusted to optimize short chain or longer chain extraction

Recovery limitations for short-chain and very long chain PFASs depending on the chosen extraction method were reported. For the short-chain PFCAs (C2-C4) an ion-exchange RSpak JJ-50 2D column is preferably used (Chen et al., 2019). Alternative extraction methods are available using superparamagnetic nanospheres coated with a polydopamine-based molecularly imprinted polymer to selectively extract PFOS (Lin et al., 2021).

New improved extraction methods are continuously developed as for example the use of solid phase microextraction (SPME), hydrophilic-lipophilic balance-weak anion-exchange/polyacrylonitrile (HLB-WAX/PAN) as a SPME coating (Olomukoro et al., 2021). Multi-residue extraction procedures using QuEChERS (SQ and EMRLipid, AQ and Z-sep+ bulk-based dSPE and AQ and graphitized carbon black (GCB)-based dSPE) are used for biota with detection limits of 30 ng/g (Alvarez-Ruiz et al., 2021). Micro solid-phase extraction requires only 2 mL of sample. (Lockwood et al., 2019)

Targeted methods are often combined with non-targeted methods in order to identify the total available fluorinated compounds present in addition to the amount of specific PFASs determined. These non-targeted methods include Total Organic Fluorine (TOF), Extractable Organic Fluorine (EOF) and Total Oxidizable Precursor Assay (TOPA) in decreasing order of range of compounds detected (Aro, Carlsson, et al., 2021).

As reported in the workshop report (see footnote 111) several studies have used TOPA for analysing surface-, ground- and wastewater (Casson & Chiang, 2018; Dauchy et al., 2017; Houtz et al., 2018; Houtz et al., 2013; Houtz et al., 2016). With TOPA, also unknown precursors for C2-C3 perfluoroalkyl carboxylic acids can be traced back when looking for legacy and emerging PFASs (Chen et al., 2019; B. Wang et al., 2020) .

Other non-specific methods are briefly addressed in the following.

A potential approach to detect total fluorine is the defluorination with sodium biphenyl (SBP) followed by various fluoride quantification methods. The method has been reported for PFCA (Musijowski et al., 2007). The authors reported a receiver rate of fluoride of above 95% and concluded that the approach shows very efficient preconcentration of analytes and achieved low detection limits. Acceptable recoveries of fluoride from different PFCAs were demonstrated. It should ,however, be noted, however, that the authors reported a low precision of the procedure. (Koc et al., 2011) added an extra step where the fluoride was, after defluorination, derivatized with triphenylhydroxysilane (TPSiOH) and analysed by gas chromatography (GC) coupled with a flame ionization detector (FID), electron capture detector (ECD) or mass spectrometer (MS). The GC methods showed comparable LODs to those of fluorometric or conductimetric methods (~1-100 µg/L).

A further potential approach is the use of ¹⁹F Nuclear magnetic resonance (NMR) spectroscopy, which has been described in (Moody & Field, 2000; Moody et al., 2001). NMR is selective and can also determine the degree of branched isomers (Weiner et al., 2013). However due to the low sensitivity of the ¹⁹F NMR technique, extensive pre-concentration or prolonged acquisition time (45 or 60 min) are required for environmental samples. The LOD for surface water is 10 µg/l after 200 times concentration (Ellis et al., 2000; Moody & Field, 2000).

The combustion ion chromatography (CIC) method can be used to estimate the amount of extractable organic fluorine (EOF) in different matrices after sample extraction (Kärrman et al., 2019; Koch et al., 2019; Miyake et al., 2007; Trojanowicz et al., 2011; von Abercron et al., 2019; Wagner et al., 2013b; Weiner et al., 2013).

A new technique that has recently been published involves high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) that can be used to determine EOF, AOF and Total Fluorine (TF) in water samples (Gehrenkemper et al., 2021). The AOF analysis relies on carbonaceous sorbents to capture organic fluorine and eliminate fluoride instead of the EOF method (Han et al., 2021).

Further the literature mentions continuum source molecular absorption spectrometry (CS-MAS) as a potential methodology for environmental samples which uses online pyrolysis and formation of metal monofluorides (e.g. AlF, InF, or GaF) at high temperatures (Qin et al., 2012). In the paper a reverse phase-high performance liquid chromatograph (RP-HPLC) was combined to both ESI -MS (electrospray ionization mass spectrometry) and CS-MAS in parallel to identify and quantify novel PFASs in environmental samples. An LOD of 1 µg/L for groundwater was reported.

In recent times, research on non-targeted screening (NTS) has led to the development of methods that allow for broad screening of samples without prior knowledge about target analytes. Unexpected or previously unknown compounds can hence be detected and identified. However, it should be noted that NTS analyses are quite complex and require a high degree of analytical expertise.

Abiotic environmental solid matrices (dust, soil, sludge and sediments)

An overview on determinations of PFASs in abiotic matrices is published in (Nakayama et al., 2019).

Existing standards for abiotic matrices focus on soil and are listed below:

• ASTM D7968-17a: The scope of the method is soil. The method is applicable to C4-C14 PFCA, C4-C8 PFSA, PFECHS, FHpPA, 6:2 FTA, 8:2 FTA, 10:2 FTA, 2H-perfluoro-2-decenoic acid and 2H-perfluoro-2-octenoic acid in concentrations above 0.025 µg/kg ds. Samples are vortexed and shaken with methanol/water and methanol/water/NH₃. No clean-up is applied. PFASs are separated on a phenyl hexyl column with a water/acetonitrile/NH₄Ac gradient and detected in MRM mode. Quantification is done by the external standard method.
• DIN 38414-14: The scope of the method is soil, sediment and sludge. The method is limited to C4-C10 PFCA and C4-C8 PFSA, with a quantification limit of 10 µg/kg dw. Samples are sonicated with methanol. Clean up on SPE-WAX followed by elution with methanol (0.1% NH₃) is only applied for sludge. PFASs are separated on a C18 column with a water/methanol/NH₄Ac(/HAc) gradient and detected in MRM mode. Quantification is done by the internal or external standard method.

In order to avoid contamination, any sampling containers need to be pre-cleaned before use. In general, samples are placed in a HDPE or PP bag, bottle or tube and refrigerated at 4°C or frozen at -20°C until analysis. Samples are freeze-, air- or vacuum-dried, then sieved and homogenized. In contrast to outdoor environmental samples, dust samples are often taken indoor in order to complete the overall picture of PFAS exposure to human beings. In general, specific vacuum cleaners are used in this regard. All types of samples (soil, sediment, sludge and dust) are commonly extracted with Soxhlet extraction, pressurized liquid extraction (PLE) or by vortexing/shaking/ultrasonication (Jahnke & Berger, 2009; van Leeuwen & de Boer, 2007). Quantification is done using labelled PFAS standards (internal or surrogate) that are added prior to extraction. Extraction solvents are methanol, alkaline methanol and, in a few studies, acidified methanol (Codling et al., 2018; Joerss et al., 2019). Sometimes acetonitrile is used in combination with water or methanol (Guo et al., 2016; Rankin et al., 2016; Ruan et al., 2015). The clean-up step is usually done on graphite carbon or SPE cartridges or by ion pair extraction (IPE)) that involves shaking/ultrasonication followed by centrifugation and clean-up of the supernatant on ENVI-Carb or an SPE cartridge (e.g., OASIS WAX, OASIS HLB or C18) under neutral or basic conditions are used. As PFASs cover a large group of different substances, extraction procedure needs to be optimized for capturing PFASs with diverse properties, especially highly hydrophobic compounds, cations and zwitterions, which strongly adsorb to solid matrices. (Munoz et al., 2018) reported methanol with ammonium acetate as best option for accurate results. It needs to be considered that dust samples are mostly analysed for volatile (neutral) and non-volatile PFAS. Different extraction solvents and/or repeated extraction steps are thus needed for the analysis of both classes of PFASs (Eriksson & Kärrman, 2015; Lankova et al., 2015; Winkens et al., 2018).

Comparison between total fluorine and targeted analysis can indicate the amount of identified PFASs in the total fluorine containing organic content. For example, only 2% of the total fluorine concentration of 157 µg/g measured in fire station dust could be attributed to targeted PFASs (Young et al., 2021). A combination of GC-MS and LC-MS/MS showed a significant increase of indoor PFASs levels in dust in China where ∑PFASs were in the range 185−913 ng/g. However, in combination with TOPA an unknown perfluoroalkyl acid (PFAA)-precursors contribution of 37−67 mol % was indicated. A daily perfluorooctanoic acid (PFOA) equivalent intake of PFAAs (C4−C12) mixtures via indoor dust were first estimated at 1.3−1.5 ng/kg bw/d for toddlers (B. Wang et al., 2021).

Recent literature (Munoz et al., 2021) investigates the PFAS input in agricultural lands, 160 PFASs from 42 classes were detected from target screening and homologue-based nontarget screening. Target PFASs were low in agriculture-derived wastes (median ∑₄₆PFAS: 0.66 μg/kg dry matter). Higher PFAS levels were reported in urban and industrial wastes, paper mill sludge, sewage sludge, or residual household waste composts (median ∑₄₆PFAS: 220 μg/kg). The fluorotelomer sulfonamidopropyl betaines (X:2 FTSA-PrB, median: 110 μg/kg, max: 1300 μg/kg) were the emerging class with the highest occurrence and prevalence in contemporary urban organic waste products.

The literature research revealed that mostly GC-PCI-MS is used as detection method for volatile PFASs in solids. For ionic PFASs however, instruments and conditions are similar to those used for analysis of aqueous matrices by LC- MS/MS. Especially C18 columns combined with water/methanol/ammonium acetate mobile phase gradients are used. However, (Munoz et al., 2021) used Orbitrap-MS or TOF-MS for detection of PFAS.  

LOD and LOQ (Limit of quantification) values differ for matrices and PFAS compound and vary from <0.01 to 10 µg/kg dw.

Air samples

For sampling high-volume air samplers can be used that collect gaseous PFASs on composite media consisting of XAD-2, polyurethane foam (PUF), and quartz-fibre filters (Martin et al., 2002; Wong et al., 2018). PUF/XAD/PUF are commonly used for collection using a high-volume air sampler, where a large volume of air (2000 m³) is sampled over a period of time over a glass fiber filter and a cartridge containing polyurethane foams. Hence both gas and particle phase PFASs are collected. Alternatively, a SPE cartridge using a low-volume air sampler can be used. Usually PFASs are extracted from XAD and PUF absorbents with solvents such as acetone and petroleum ether using Soxhlet (Martin et al., 2002; Shoeib et al., 2008) or pressurised liquid extraction (PLE) (Wong et al., 2018). For air samples of neutral PFASs, ISOLUTE ENV+ and Oasis HLB cartridges have been widely used as trapping materials. PFASs collected on such cartridges are generally eluted with methanol (Padilla-Sanchez et al., 2017). (Yao et al., 2018) reported on a two-layer SPE which consisted of higher carbon (HC)-C18 and weak anion exchange (WAX) material.

Where active air sampling uses a pump to collect gasses, passive sampling relies on the natural gas diffusion process. The advantage of active sampling is that a defined amount of gas can be collected, which is not possible in passive sampling. Passive samplers are mostly small devices that can be carried on the body for example.^{[1]https://www.zefon.com/passive-vs-active-air-sampling} For passive sampling of air, solvent-impregnated polyurethane foam (SIP) has been developed (Shoeib et al., 2008). Soxhlet extraction is the method of choice when PFASs are collected from SIP, and solvents such as acetone/petroleum ether (1:1), methanol or ethyl acetate are usually used. In addition, cold column extraction with ethyl acetate has been reported by (J. Li et al., 2011; Y. Tian et al., 2018). Additional clean-up by ENVI-Carb is employed in some cases (J. Li et al., 2011; Y. Tian et al., 2018). Airborne particulate matter collected on filters is generally subjected to Soxhlet extraction with dichloromethane or ultrasonic extraction with methanol (Guo et al., 2018).

According to (van Leeuwen & de Boer, 2007), typical air sampling volume are 300–2,000 m³ (outdoor) and 20–200 m³ (indoor). However, volumes could be reduced over the last years for indoor air samples to 0.2–8 m³ (Padilla-Sanchez et al., 2017; Yao et al., 2018). Particulate matter is generally collected on a glass- or quartz-fibre filter (Guo et al., 2018; Wong et al., 2018). It seems that sampling issues are challenging as no standardized methodology is available.

Sampling issues are the main challenge when monitoring PFASs in air. As indicated in the workshop report (see footnote 111) for detection of low levels of PFASs in air the elimination of background contamination is crucial. To eliminate such contaminants XAD and PUF absorbents used for air sampling are rinsed before use by Soxhlet extraction with organic solvents. SPE cartridges are washed with methanol or ethyl acetate and dried with high-purity nitrogen gas before use. The samplers are typically placed in a polypropylene (PP) container or wrapped with aluminium foil and stored at -20°C until analysis (Martin et al., 2002; Padilla-Sanchez et al., 2017; van Leeuwen & de Boer, 2007; Yao et al., 2018).

As regards instrumental analysis GC-MS with either electron ionisation (EI) or chemical ionisation (CI) in selected ion monitoring (SIM) mode is the commonly applied method for neutral PFASs (J. Li et al., 2011; Shoeib et al., 2008; Yao et al., 2018), while for ionic PFASs (U)HPLC-MS/MS with electrospray ionisation (ESI) is applied (J. Li et al., 2011; Ying Tian et al., 2018; Yao et al., 2018). The method is similar to that used for water samples.

An example of air sampling is the use of a cryogenic air sampler (CAS), which was used to collect all atmospheric components simultaneously. This was followed by non-target analysis through PFASs homologue analysis by UPLC-orbitrap. A total of 117 PFAS homologues (38 classes) were discovered, 48 of which (13 classes) were identified with confidence level 4 or above (Yu et al., 2020). Dansyl chloride derivatization was found to be an improvement of the detection of fluorotelomer alcohols in air, allowing detection limits of 1.5 pg/m³ (Takemine et al., 2018).

4.18.2 Human samples

It should be highlighted that within the EU Human Biomonitoring (HBM) HBM4EU^{[1]www.hbm4eu.eu} network PFASs have been prioritized so that harmonized protocols are available for the measurement of PFASs in the general population in Europe.^{[2]https://www.hbm4eu.eu/the-substances/per-polyfluorinated-compounds/} In this regard a network of laboratories that proved their ability to measure PFASs in human matrices in a quality assurance scheme organized by the project has been established. The work related to harmonized HBM data is ongoing and will most likely be continued in the Partnership for the Risk Assessment of Chemicals (PARC) which recently applied for funding within the HORIZON EUROPE program. It is expected that the network will start in the course of 2022. The coordination has been taken over by ANSES, France.^{[3]ANSES is participating in the preparation of a European Partnership for the Assessment of Risks from Chemicals | Anses - Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail}

(Point et al., 2019) investigated in their paper analytical challenges with specific attention to interlaboratory studies. In particular, they looked into differences in the analytical methods that caused inconsistent results for PFASs analysis. As primary source the adsorptive properties impacted by the solvent composition of the different compounds were reported. Based on these finding they investigated with systematic experiments appropriate solvent composition and the effect of container material. The authors concluded that additional experimental studies as well as transparent communication of analytical difficulties are recommended in order to further develop robust standardized analytical methods for PFASs. Plasma, serum and breast milk could be identified as the main target matrices for human biomonitoring (Lee et al., 2018; Lindh et al., 2012; Poothong et al., 2017; Rogatsky et al., 2017; Wu et al., 2017). Some recent studies are also focusing on non-invasive samples such as urine, hair and nail (e.g.(Martin et al., 2019) (N. Li et al., 2021; Ruan et al., 2019) (Piva, Fais, et al., 2021; Piva, Giorgetti, et al., 2021)). When measuring human samples, the focus of the analytics is not only given to the substance itself but also on parent compounds, its metabolite(s) and transformation product(s) or other chemical products formed in the body or the environment. Blood and urine are collected in a PP tube or bottle and stored at -20°C until analysis. Nail and hair samples are collected using pre-cleaned nail cutter or scissors and stored in a PP centrifuge tube at room temperature. Nail and hair samples are often washed with water or acetone to remove external contamination and dried before analysis.

To eliminate matrix interference by lipophilic components in the samples appropriate pre-treatment options are necessary. Various pre-treatment and extraction methods such as alkaline digestion, acetonitrile protein precipitation, SPE, liquid-liquid extraction (LLE) and ion pair exchange (IPE) are available. Removal of lipid components needs to be considered. Various methods are available like sample freezing after SPE clean-up, use of graphite carbon (e.g. ENVI-Carb) clean-up (Hanssen et al., 2013) (Berg et al., 2014), or the addition of 1-methyl piperazine to the LC-MS/MS mobile phase (Gao, 2018). In addition, weak anion exchanger (e.g. Oasis WAX) can be used for clean-up. (Wang et al., 2018). Recent work has shown that the type of extraction (ion-pair liquid-liquid extraction, solid-phase extraction (SPE), using hydrophilic-lipophilic (HLB) or weak anion exchange (WAX) sorbents) shows different efficiencies for different PFAS, indicating that care has to be taken in the choice of sample preparation (Kaiser et al., 2021; Salameh, 2021). The sample volume required for PFASs analysis in blood has decreased during the last decade from ml to tens of µl.

High performance liquid chromatography coupled with tandem mass-spectrometry (LC-MS/MS) is mostly used as analytical method. In general, the applied instrumental method is similar to that used for water samples. FTOH and FTOH precursors (FTMAC and PAPs) and their metabolites can be measured by targeted methods, by low- or high-resolution mass spectrometry. Cationic PFASs (such as betaines used e.g. in firefighting foams) can be measured using specific methods used for environmental matrices as well.^{[4]HBM4EU_D4.9_Scoping_Documents_HBM4EU_priority_substances_v1.0-PFAS.pdf}

Achievable LoQ values in serum are 0.01–0.1 ng/ml depending on the PFAS compound (Colles et al., 2020). Especially PFOS, but also PFBS, PFBA, PFOA, PFNA and PFHxS are the predominant PFASs found in human samples. Also, LC- HRMS (high resolution MS) has been used for PFASs detection, reaching similar detection limits (Piva, Fais, et al., 2021; Piva, Giorgetti, et al., 2021). It should be noted that analyses are sometimes performed according to ISO standards (for example ISO DIN21675, 2019 (Martin et al., 2019; Ruan et al., 2019).

The difference between EOF (determined by CIC) and targeted analysis gives an indication of the amount of undetected PFASs in human samples. Additional focus is also put on looking at enantiomer fractions using chiral chromatography or SFC to improve PFASs characterization (Wang et al., 2011; Zhao et al., 2019).

5. Cost considerations

This report shows that there is a large variety in analytical approaches to analyse PFASs in various matrices. Therefore, it is very difficult to set prices for a typical analysis. Below a number of parameters that have to be taken into account for price setting are reported.

• Matrix. A number of matrices like water, soil, dust have already prescribed methods. Other matrices like consumer products, biological material or other complex mixtures need a more tailored approach and require often a more elaborate sample preparation.
• Number of samples. Measurement of a higher number of samples will lower the price per sample due to more effective sample preparation as well as more effective instrument use.
• Technique used. For targeted and untargeted analysis chromatography coupled to mass spectrometry is most often used. Total fluorine values are mostly measured with ion chromatography. Prices depend on the technique used.
• Number of PFASs to detect. A number of methods have a definite list of PFASs which are detected. Additional compounds require additional calibrations, internal standards and instrument settings.
• Targeted and untargeted. Targeted methods are often fixed with known MRM transitions and automated data interpretation workflows. Untargeted analysis requires skilled scientists and the right data interpretation tools and experience.
• Post analysis. The obtained data can be used for advanced modelling or other data visualization approaches.

Therefore, exact prices cannot be provided at that stage. A rough estimation is 100 €/ sample for a standardized targeted LC-MS/MS analysis in a commercial lab (one single target substance). To cover more PFASs (about 30 ionic PFASs are commonly measured) higher prices are estimated depending on the matrix and clean-up (ca. 300 €/ water sample). These prices increase with increasing level of complexity. For more complex questions like untargeted screening, commercial labs are most often not sufficiently equipped and universities, research institutes or high-end commercial labs need to be approached. In such cases prices can increase significantly.

6. Conclusions

In the following, some general conclusions and recommendations for the analysis of PFASs are given.

• For some matrices there are well-established standards available (or standards that are used although not specifically designed for that matrix) that exclusively focus on a targeted sub-set of PFASs (mostly 10–30 individual PFASs). There are standards available for example by the International Organization for Standardization (ISO), by the US EPA, the European Committee for Standardization, or the German institute for Standardization (DIN).
• A large number of scientific publications is available covering method development and method improvement studies. Especially with the increasing awareness for PFASs in the recent years, the number of publications increased and is still increasing.
• The publications in the scientific literature spans from purely experimental topics to the use of standard methods for e.g. new matrices. It needs to be taken into account that some methods described are still in a stage that only very specialised laboratories can apply them, while others are validated and can be used in a common laboratory.     
• There are no standards available for total fluorine methods or the Total Organic Precursors assay (TOPA). Commercial laboratories, however, offer these measurements (often in combination with targeted approaches).
• US EPA is currently developing a standard operating procedure tool for determination of Total Organic Fluorine (TOF) in environmental samples. Additionally, the need for a standard procedure for TOPA measurements of PFAS precursors in environmental matrices is considered by EPA.^{[1]https://www.epa.gov/water-research/pfas-analytical-methods-development-and-sampling-research}
• In the EU, a first interlaboratory comparison of Extractable Organic Fluorine (EOF) and fluorine mass balance in sludge and water matrices demonstrated promising accuracy, robustness and reporting limits but poor extraction efficiency was observed for some targets (e.g. trifluoroacetic acid) (Kärrman et al., 2021).
• When results of targeted analysis are compared to measurements of total fluorine (TOF, EOF, AOF) or PFAS-precursor analysis (TOPA) it is evident that the targeted methods “miss the whole picture”, meaning that a lot of PFASa are overlooked.
• Often, individual PFASs contribute only to a small fraction of the total fluorine in a sample, and therefore guidance values that have been derived for single substances may be of limited value in assessment of exposure and risk.
• For the matrix “food contact materials” there is a limit value based on the total fluorine concentration: The Danish Food and Veterinary Administration suggested an indicator value of 10 μg/dm² Organic Fluorine (OF) for food packaging, where fluorine concentration in paper below this value can be assumed to not be treated with PFASs.
• For firefighting foams, an NGO (Clean Production Action) defines “PFAS-free” as zero intentionally added PFASs to the product and PFASs contamination (measured as TOF) in the product must be less than 0.0001 percent by weight of the product (1 ppm)^{[2]https://www.greenscreenchemicals.org/certified/fff-standard}.

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Appendix

A. Search strategy for PFASs analysis in various matrices

The strategy for the comprehensive literature search on PFASs analysis methods in various matrices is explained in detail in the following.

a. Information sources

The following information sources have been included in the search for analytical measurements of PFAS.

• Screening of available information within the group and known review articles like Glüge et al.
• Scientific peer-reviewed literature (Pubmed, EuroPMC)
• Standardization bodies (incl. Draft standard methods if available)
• Application notes from laboratories and suppliers of analytical equipment
• Eco-labels and respective required analytical methods (Grüner Knopf, Blue Angel, Nordic Swan)
• Agencies (incl. work by ECHA (C9-C14, PFHxA, ADONA …) and Stockholm Convention)
• Projects (HBM4EU, NORMAN…)

b. In/exclusion criteria of the literature search

In Table 3 the in- and exclusion criteria for the search are shown. In addition to the shown criteria, Ramboll has reduced the search to the title and abstracts in the case that too many hits have been found (>500-1000).

Table 3 In/Exclusion criteria

As observable from the table, review articles are excluded from the literature research, and instead the primary publication will be considered.

c. Search string

The search strings are divided into three parts, that will be connected logically:

1. Synonyms covering PFASs
2. Synonyms covering analytical measurement
3. Synonyms terms covering the matrix

Please see here an example:

PFAS* OR PFCs OR PFAA* OR PFOS OR PFOA OR perfluor* OR polyfluor*

AND

Analy* OR test* OR standard* OR method* OR determin* OR investi*

AND

Textil* OR leather OR apparel OR upholstery OR garment OR fabric OR clothing OR “outdoor” OR “impregnation”

In the following, the three-parts of the search string will be highlighted in more detail.

Table 4 shows the synonyms covering PFASs (and any substances falling under the current restriction proposal). To make sure, that also CF2/CF3 substances were covered, the search term “fluorin*” was included to capture also these substance identities.

Table 4: Synonyms covering PFASs

Note: ^{[1]The following terms were not found in PubMed: PFHPDA, PFNDA, PFUnDS, PFUnS, PFDODS, PFTRDS, PFTeDS, PFHXDS} 

Table 5 shows the synonyms covering the analytical measurement.

Table 5: Synonyms covering the analytical measurement

Table 6 shows the synonym terms covering the individual matrices. With the aim to find relevant search terms, the project team consulted Glüge et al., 2020 for relevant usages and/or functions within the PFAS applications (mainly the electronic supplemental data, see here).

Table 6: Synonym terms covering the matrix

d. Documentation Sheet

The information sheet is built in Excel and contained information on the relevant pub|lications identified by literature search is easily accessible by for example sorting via text search. Additional, information on standard methods is added. Every matrix discussed in the report has a separate sub-sheet. Publications or standards which could be assigned to more than one category are available in each respective sub-sheet.

The documentation sheet contains: 

• Bibliographic information on the reference (author, title, journal, year, DOI)
• Substances addressed (if available with CAS)
• Sample amount used
• Pre-treatment of sample
• Extraction method
• Brief generic method classification
• Clean-up method
• Quantification method
• Working range of the method
• Possible matrices
• Reported levels – in the case indicated 
• Information on validation of the method 
• Limitations (e.g. reported matrix effects)
• LOD and LOQ
• Further comments on the matrix

Download information sheet here. 

About this publication

Analytical Methods for PFAS in Products and the Environment

This publication has been prepared by Miriam Schöpel, Griet Jacobs, Jan Jordens, Guido van Ermen, Stefan Voorspoels, Maren Krause and approved by Alexandra Polcher on behalf of the Norwegian Environment Agency.

ISBN 978-92-893-7261-9 (PDF)
ISBN 978-92-893-7262-6 (ONLINE)
http://dx.doi.org/10.6027/temanord2022-510

TemaNord 2022:510
ISSN 0908-6692

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Published: 8/3/2022
Updated 1/4/2022

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