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Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (Anguilla rostrata): Recommendations for Methods Standardization
Citation:
Ruyle, B., H. Pickard, L. Schultes, F. Fredriksson, A. Heffernan, D. Knappe, H. Lord, P. Meng, Marc A. Mills, K. Ndungu, P. Roesch, J. Rundberget, Daniel R. Tettenhorst, J. Van Buren, C. Vogel, D. Westerman, L. Yeung, AND E. Sunderland. Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (Anguilla rostrata): Recommendations for Methods Standardization. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 57(48):20159-20168, (2023). https://doi.org/10.1021/acs.est.3c04560
Impact/Purpose:
A comparison of EOF measurements among seven labs indicates that a standardized method for sample extraction, instrumental analysis, and data processing is critically needed. Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis are currently unavailable including for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here we evaluate the reproducibility, precision, and accuracy of EOF based on an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film forming foam. Among all labs, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from at least one replicate extract for all labs fell within one standard deviation of the interlaboratory mean for groundwater and five of seven labs for eel. Recoveries of a PFAS spike mixture across all labs for EOF measurements in both groundwater and eel were similar to criteria (±30%) for standardized targeted PFAS methods. Instrument operational variation of the CIC such as replicate sample injections was the greatest source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend the analyst carefully considers and reports potentially confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds.
Description:
Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film-forming foam. Among all laboratories, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from all laboratories for at least one replicate extract fell within one standard deviation of the interlaboratory mean for groundwater and five out of seven laboratories for eel. PFAS spike mixture recoveries for EOF measurements in groundwater and eel were close to the criterion (±30%) for standardized targeted PFAS methods. Instrumental operation of the CIC such as replicate sample injections was a major source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend that analysts carefully consider confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds.
URLs/Downloads:
DOI: Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (Anguilla rostrata): Recommendations for Methods Standardization