Environmental Standards, Inc.
Mr. Blye has more than 35 years of diversified experience in the field of environmental chemistry; his experience includes field data collection and environmental sampling and the planning, development, and execution of field sampling and analytical projects. He specializes in the interpretation of organic and inorganic analysis data and the development of field procedures for the collection of representative groundwater, surface water, soil, air, and multi-media samples. He has extensive experience in EPA organic and inorganic analytical methodology and analytical data validation. He has a strong environmental forensics background and specializes in the analytical chemistry of PFAS, PCBs and Dioxins/Furans.
Issues with the Quantitation and Identification of PFAS in Environmental Matrices
Analysis for per- and polyfluoroalkyl substances (PFAS) in environmental samples has become a critical issue over the last several years, particularly in the absence of US EPA-approved methods for matrices other than finished drinking water (US EPA Method 537). There are several published ASTM and ISO analytical methods for the determination of PFAS in samples, but none have gained widespread use by commercial laboratories in the United States. Commercial laboratories have modified the published methods to address more complex matrices, such as wastewater and soil/sediment samples, and typically refer to these methods as “Method 537 Modified.” However, these methods and modifications are highly variable in quantitation techniques and do not address interferences typically known for complex environmental samples. Because of these differences in analytical techniques, one of the significant issues facing the environmental community is the lack of data comparability. Several quantitation techniques, including external standard, internal standard, and isotope dilution are being utilized to determine PFAS concentrations. In addition, the internal standard and isotope dilution techniques have an added variable, that being which labeled compounds are being utilized for quantitation. Isotope dilution is not specifically identified in the analytical methods being modified; however, laboratories are selecting their own labeled compounds to be used. To make a complex situation even worse, some of the published methods indicate that branched and linear PFAS standards must be used to identify and quantitate PFAS. The inclusion of branched and linear compound standards and the lack of branched isomer resolution and separation criteria are particularly important factors affecting data consistency and comparability. Branched PFAS compound quantitation is often done in an “apples to oranges” manner by referencing the quantitation to a linear calibration standard. Chromatographic interferences from unknown PFAS or other organic contaminants are often present in sediment samples that further complicate data quality. Lastly, in June 2019 the US EPA issued draft Method 8327 for PFAS analysis of aqueous matrices other than drinking water. The method validation show significant issues in laboratories trying to implement a uniform method. This presentation will review and show several examples of issues with PFAS data and the variability in sample quantitation.