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Laboratory development and validation of vapor phase PFAS methods for soil gas, sewer gas, and indoor air
Citation:
Hayes, H., C. Lutes, N. Watson, D. Benton, D. Hanigan, S. McCoy, C. Holton, K. Bronstein, B. Schumacher, J. Zimmerman, AND A. Williams. Laboratory development and validation of vapor phase PFAS methods for soil gas, sewer gas, and indoor air. Environmental Science: Atmospheres. Royal Society of Chemistry, Cambridge, Uk, 5:94-109, (2025). https://doi.org/10.1039/D4EA00084F
Impact/Purpose:
There is currently no standard sampling and analysis method for vapor phase per- and polyfluoroalkyl substances (PFAS) in soil gas, sewer gas, and indoor air. Vapor intrusion (VI) to occupied buildings occurs due to pressure differentials between indoor air and contaminated soil gas. Such a method is critically needed given the prevalence of PFAS as subsurface contaminants (e.g., manufacturing facilities and fire-fighting training locations). A substantial number of PFAS are expected to be sufficiently volatile and sufficiently toxic via inhalation to require VI consideration. We have validated a thermal desorption GC/MS/MS method for measurement of fluorotelomer alcohols and perfluorooctanesulfonamides collected on multi-bed sorbent tubes. We identified critical weaknesses when the method is applied to perfluoroalkyl carboxylic acids.
Description:
There is no standard sampling and analysis method for vapor phase per- and polyfluoroalkyl substances (PFAS) that can be routinely applied to soil gas, sewer/conduit gas, and indoor air samples. We have validated a thermal desorption GC/MS/MS method for the measurement of a set of fluorotelomer alcohols and perfluorooctanesulfonamides collected on multi-bed sorbent tubes. Applications to perfluorocarboxylic acids were also evaluated since there is debate regarding under what circumstances these compounds could be observed moving into gas phase. Perfluorooctanoic acid (PFOA) met Method TO-17 calibration requirements when calibrated using National Institute of Standards and Technology (NIST) traceable standard solutions introduced through the thermal desorption system and using multiple reaction monitoring (MRM) transitions based on precursor mass ions identified in the PFOA spectra. However, subsequent detailed studies suggested that PFOA was decomposing during the thermal desorption sample introduction step when comparing two alternative GC/MS sample introduction techniques. The primary peak resulting from the thermal desorption of PFOA standard had spectra consistent with perfluoro-1-heptene (PFHp-1), suggesting that a degradation reaction was occurring. Therefore, the identification of the PFCA compounds in this method is currently subject to a potential positive interference from the corresponding perfluoroalkene and other thermally labile PFAS. Thus, it may be beneficial to limit the application of the thermal desorption GC/MS/MS method to the fluorotelomer alcohols and perfluorooctanesulfonamides and use a parallel solvent extraction approach to quantify the PFCA-related compounds. Method validation including desorption efficiency, second source verification, storage stability and method detection limit tests were successfully completed for the fluorotelomer alcohols and perfluorooctanesulfonamides target analytes.
URLs/Downloads:
DOI: Laboratory development and validation of vapor phase PFAS methods for soil gas, sewer gas, and indoor air