An Integrated Approach for Determination of Total Per- and Polyfluoroalkyl Substances (PFAS)

Per-
and polyfluoroalkyl substances (PFAS) are difficult to analyze
in environmental media due challenges such as extraction recovery
and lack of analytical standards. The total oxidizable precursor (TOP)
assay and suspect screening analysis coupled with semiquantitative
(SQ) concentration estimates are two approaches to assess total PFAS
in environmental media, but studies are needed to optimize workstreams
for total PFAS analysis. This study applied two soil extraction methods,
TOP assay, and SQ analysis to three aqueous film-forming foams (AFFFs)
and three AFFF-impacted soils. In soils, the total PFAS estimated
with results from an extraction method utilizing sequential acidic
and basic solvents led to a 35% increase in precursors during TOP
assay relative to results from a basic solvent only extraction in
one of three soils tested, but concentrations did not increase significantly
in remaining soils. Furthermore, sample-specific dilution schemes
were required to overcome matrix effects caused by the acidic extraction
step that influenced estimates of total PFAS by SQ analysis. The results
highlight that there is not an advantage to routine application of
an acid extraction step in PFAS-impacted soils. In three AFFFs, suspect
screening of post-TOP samples identified eight classes of PFAS present
after oxidation. Concentrations of three classes increased, suggesting
they are new TOP end points. Concentrations of the remaining five
classes either remained constant after TOP or exhibited slight decreases.
As a result, combined TOP and SQ workstreams may yield the most representative
assessment of total PFAS composition and concentration. The eight
classes of PFAS present after TOP did not degrade in harsh conditions.
Some are structurally similar to PFCAs and PFSAs and are known to
occur in the environment, suggesting a similar degree of persistence
and a need for more routine monitoring.