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The evolution of PFAS analytical methods over the last decade

The evolution of PFAS analytical methods over the last decade

This summer, the EPA released Draft 1633 as an isotope dilution method for analyzing per- and polyfluoroalkyl substances (PFAS) in non-drinking water matrices. With this release, the use of modified drinking water methods (i.e., modified EPA 537) may be a thing of the past. However, at this time, different methods are still available and, depending on data quality objectives, regulatory agencies, clients, etc., the methods used for any project can vary—and all come with their own unique challenges.

A brief history of PFAS analytical methods

The first EPA method used to analyze PFAS was EPA 537 (2009), which was specific to drinking (potable) water. As drinking water was impacted by PFAS, investigations into non-drinking water matrices (groundwater, surface water, wastewater, sediment, soil, etc.) began, resulting in laboratories developing their own methods based on the EPA 537 method. Agencies, such as the Department of Defense (DoD), developed quality control guidance to evaluate these modified PFAS analysis methods for consistency. Non-potable water and solid matrices reference methods were released by the EPA and other organizations, such as the American Society for Testing and Materials (ASTM), starting in approximately 2014. Since then, the methods and PFAS parameters available for analysis have constantly evolved. The table below lists some of the most common methods and their associated matrix, calibration type, and number of targeted PFAS analytes.

* Quantitation by isotope dilution is an option in the method. If target analyte doesn’t have an exact isotope match, analytical report must indicate if correction was done or not.

Note: Laboratories may indicate “modified” when calibration type or # of PFAS is different than the reference method, unless the modification is allowed in the method.

Draft Method 1633

For non-potable water matrices, the fourth draft of Method 1633 is available as of July 2023 and has been finalized for the following aqueous matrices: wastewater, surface water, and groundwater. The EPA anticipates issuing a final version of Method 1633 that incorporates criteria for solid matrices (soil, biosolids, sediment, fish tissue) and landfill leachates by the end of 2023. While Draft Method 1633 will not be required nationally for Clean Water Act compliance monitoring until promulgated and published in 40 CFR Part 136.3, the EPA is recommending its use. Laboratories still use other PFAS-related analytical methods (i.e., EPA 537.1 modified) and/or laboratory-specific standard operating procedures (SOPs), most of which include the use of isotope dilution to quantify PFAS concentration.

For additional information, contact our team of PFAS experts or learn more about Barr's PFAS services.

About the authors

Terri Olson, senior data quality specialist, has nearly 40 years of experience working with analytical laboratory data. As a senior consultant, her responsibilities include periodic review and auditing of analytical facilities and their procedures; review of laboratory analytical data involving per- and polyfluoroalkyl substances (PFAS), volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), pesticides, general chemistry, and metals; and review of various agency methods and guidance documents. She has considerable experience with the wide variety of regulatory methods used for environmental analyses and has worked with many laboratories regarding various PFAS analyses (e.g., modified EPA 537 and Draft EPA 1633).

Samantha Schirmer, senior data quality specialist, has nearly 10 years of experience with data quality assurance and quality control (QA/QC), laboratory procedures, and the review of analytical data. She is skilled with the Food and Drug Administration’s Current Good Manufacturing Practices (CGMPs), ISO 17025 and ISO 9001, and the Drug Enforcement Agency’s controlled substance handling practices. Samantha has industrial laboratory experience as both an environmental organics laboratory manager and director of quality assurance/quality control. Samantha has performed review of laboratory data involving PFAS, VOCs, SVOCs, general chemistry, and metals analyses as a consultant.

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Terri Olson, Senior Data Quality Specialist
Terri Olson
Senior Data Quality Specialist


Samantha Schirmer, Senior Data Quality Specialist
Samantha Schirmer
Senior Data Quality Specialist
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