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Understanding analytical interferences in targeted PFAS methods: A case study in shellfish
Citation:
Bangma, J., J. McCord, J. Petali, K. Buckman, C. Chen, N. Giffard, AND M. Strynar. Understanding analytical interferences in targeted PFAS methods: A case study in shellfish. North America SETAC, Pittsburg, PA, November 13 - 17, 2022.
Impact/Purpose:
The long term implications of this work is that PFPeA maybe over reported in the literature in biological samples. In short, if studies reporting detected PFBPeA in biological matrices used low-resolution mass spectrometry techniques, an interfering compound may be falsely identified and reported as PFPeA. This knowledge can help future PFAS researchers identify the difference between PFPeA and the interfering compound prior to publishing PFPeA bio-monitoring results.
Description:
The investigation of per- and polyfluorinated alkyl substances (PFAS) in environmental and biological samples relies on both high- and low-resolution mass spectrometry (MS) techniques. While high-resolution MS (HRMS) can be used for identification of novel compounds, low-resolution MS/MS is the more commonly-used and affordable approach for studies examining previously identified PFAS through targeted PFAS analytical methods. To date, targeted studies of PFAS in biological matrices (e.g. blood, serum, egg yolk, placenta, chocolate, etc.) have identified instances where matrix-derived interfering compounds are capable of impacting PFOS, PFHxS, PFPeA, and PFBA quantitation on low-resolution instrumentation. These interfering compounds match the monitored fragmentation patterns of the PFAS under question and can lead to overreporting of PFAS in the literature. Of note, PFPeA and PFBA are two of the smaller PFAS observed in biological and environmental samples, and both have only one major transition for MS/MS monitoring, preventing the use of ion ratios of additional transitions for verification. Therefore, when our lab observed up to 80 ng/g wet weight of PFPeA (263→219 Da) in numerous shellfish samples, we investigated further using HRMS and identified a PFPeA interfering compound at 263.1288 Da and putatively assigned the compound as an unsaturated dicarboxylic acid with a level 3 confidence on the Schymanski scale. With further method development, we were able to establish an additional MS/MS transition for the PFPeA interferent in shellfish samples as well as establish improved chromatographic separation. Therefore, in support of PFAS analysis on low-resolution instrumentation, the authors would recommend additional methods to confirm possible PFAS analytical interferences in biological and environmental samples.
