Glossary

Reference Standard (material): In this report reference standard refers to the chemical substance or material that is needed for calibrating the corresponding instrument. Reference standards can come in various forms, including pure substances, standard solutions of known concentration, and certified reference materials. The choice depends on the analytical method and the nature of the samples being analysed. Reference standards are used for various purposes in analytical chemistry, primarily for calibration, quality control, and validation of analytical methods. These standards serve as a basis for comparing and quantifying the concentration or properties of analytes in unknown samples. Key aspects of reference standards in chemical analysis are:

Calibration & Quantification:
Reference standards are used to calibrate analytical instruments. By analysing a series of standard solutions with known concentrations, a calibration curve or equation is established. This calibration curve can then be used to relate the instrument response to the concentration of the analyte in unknown samples. The response of the instrument to the unknown sample is compared to the calibration curve to determine the concentration or amount of the analyte present.
Quality Control:
Reference standards are crucial for quality control purposes. Analysts use them to ensure the accuracy and precision of their measurements. Regular analysis of reference standards allows for monitoring the performance of the analytical method and detecting any instrumental drift or degradation.
Method Validation:
When developing or validating a new analytical method, reference standards are often used to assess the method's accuracy, precision, linearity, and other performance characteristics. This helps ensure that the method is suitable for its intended purpose.
Certified Reference Materials (CRMs):
Some reference standards, known as certified reference materials (CRMs), are characterized by a certifying body to provide a reliable reference value for a particular property or analyte. CRMs are especially useful for inter-laboratory comparisons and ensuring traceability of measurements.
Internal Standards:
In addition to external reference standards, internal standards are sometimes used within a sample. An internal standard is a substance added in a known amount to all samples and standards before analysis. It helps correct for variations in sample preparation, instrument response, and other factors.

Matrix effect: The term "matrix effect" in chemical analysis refers to the impact of the sample matrix on the accuracy and precision of analytical measurements. In analytical chemistry, samples are often complex mixtures containing various components, and the matrix is the combination of all these components other than the analyte of interest. The matrix can affect the performance of analytical instruments and methods in several ways, leading to challenges in obtaining reliable and accurate results. Some key aspects of matrix effects in chemical analysis are:

Interference with Analyte Detection:
The presence of matrix components can interfere with the detection of the analyte. For example, in spectroscopic techniques like mass spectrometry or atomic absorption spectroscopy, matrix elements may absorb or scatter the analytical signal, making it difficult to distinguish the analyte signal from background noise.
Ionization Suppression or Enhancement:
In techniques like liquid chromatography-mass spectrometry (LC-MS), the matrix can influence the ionization efficiency of the analyte. This can result in either suppression or enhancement of the analyte signal, leading to inaccurate quantification.
Matrix-Induced Calibration Errors:
Calibration curves established using standard solutions may not accurately represent the response of the instrument in the presence of a complex matrix. This can lead to calibration errors and affect the accuracy of concentration measurements.
Matrix Effects in Sample Preparation:
The choice of sample preparation method can also be influenced by the sample matrix. For example, certain matrix components may require additional sample clean-up steps to reduce interference.
Matrix-Matched Standards:
To mitigate matrix effects, analysts often prepare matrix-matched standards. These standards are prepared in a similar matrix as the sample to account for the effects of the matrix on the analytical signal.
Matrix Effects in Elemental Analysis:
In techniques such as inductively coupled plasma mass spectrometry (ICP-MS), the matrix can affect the ionization efficiency of different elements, leading to matrix-dependent responses.
Matrix-Induced Drift and Baseline Changes:
Some analytical instruments may experience baseline drift or changes in sensitivity due to the continuous introduction of different matrix components, particularly in continuous flow systems.

To address matrix effects, researchers employ various strategies, including method development and optimization, use of internal standards, matrix-matched calibration standards, and sample preparation techniques that minimize interference. Understanding and managing matrix effects are crucial for obtaining accurate and reliable analytical results in complex sample matrices.

Targeted, non-targeted or suspect screening analysis are three approaches used in chemical analysis, each with a distinct focus and purpose:

Targeted Analysis:

Focus: Specific identification and quantification of a predefined set of known analytes.

Purpose: Used when the identity and concentration of specific compounds are already known or suspected.

Applications: Common in quality control, routine testing, and regulatory compliance where emphasis is on specific substances.

Non-Targeted Analysis:

Focus: Comprehensive characterization of compounds in a sample without predefined targets.

Purpose: Exploratory approach to discover and identify a broad range of compounds.

Applications: Employed e.g., in environmental monitoring and forensic analysis to uncover the full chemical profile of a sample.

Suspect Screening Analysis:

Focus: Systematic identification and prioritization of potential compounds based on prior knowledge or suspicion.

Purpose: Combines elements of targeted and non-targeted approaches, allowing for more efficient identification of specific compounds of interest.

Applications: Commonly used in environmental monitoring, food safety analysis, and forensics, where specific contaminants or compounds associated with particular activities are targeted.