Per- and polyfluoroalkyl substances (PFAS) are difficult to analyze in environmental media due to a lack of analytical standards. The total oxidizable precursor (TOP) assay and suspect screening coupled with semiquantitative concentration estimates (SQ) are two approaches to assess total PFAS in environmental media, but studies are needed to optimize workstreams for total PFAS analysis. This study applied TOP assay and SQ analysis to 3 aqueous film-forming foams (AFFFs) and 3 AFFF-impacted soils. Suspect screening of post-TOP samples identified 9 classes of PFAS present after TOP. Oxidizable precursors are traditionally calculated as the increase in perfluoroalkyl carboxylates (PFCAs) following TOP. Suspect screening identified increases in concentrations of multiple, additional PFAS classes, suggesting there are additional TOP endpoints that should be included as part of total PFAS estimates. Suspect screening of post-TOP soil extracts also observed new TOP endpoints, confirming their relevance in site media. New TOP endpoints identified in this study are recalcitrant to harsh conditions and structurally similar to PFCAs and PFSAs, suggesting a similar degree of persistence and a need for routine monitoring in the environment. Study results suggest that combined TOP and SQ workstreams may yield the most representative assessment of total PFAS composition and concentration. When the optimized workstream was applied to a contemporary AFFF, the combined TOP and SQ workflow highlighted a large fraction of unidentified PFAS. This led to discovery of 9 new classes of PFAS that may serve as environmental markers of recent AFFF releases.

An integrated approach for determination of total per- and polyfluoroalkyl substances (PFAS)

ACS Spring 2022

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