Per- and polyfluoroalkyl substances (PFASs) are widely used anthropogenic chemicals. The unique properties of PFASs lead to a variety of applications including fluoropolymer production, civilian and military firefighting operations, stain repellents and food contact paper. Two long-chain PFASs, perfluorooctane sulfonate and perfluorooctanoic acid, were historically produced in large quantity, but a manufacturing shift towards short-chain PFASs and fluorinated replacements started in the early 2000s due to health implications. Many new PFASs are proprietary and include functional groups that can degrade to dead-end products such as perfluoroalkyl carboxylic and sulfonic acids (PFCAs and PFSAs). To determine concentrations of unidentified PFCA and PFSA precursors, the total oxidizable precursor (TOP) assay was developed. In the process, many precursor compounds are oxidized to PFCAs and PFSAs that can be readily quantified by existing analytical methods. To date, little information is available about the fate of a recently discovered perfluoroalkyl ether acids (PFEAs) in the TOP assay.  The aims of this research are to (1) determine the fate of eight perfluoroalkyl ether carboxylic acids (PFECAs), including GenX; four polyfluorinated ether acids (Nafion by-products 1 and 2, ADONA, NVHOS); and one chlorofluoroalkyl ether sulfonic acid (F-53B) in the TOP assay; and (2) determine the role of hydroxyl radicals and sulfate radicals in the TOP assay. The eight tested PFECAs and F-53B were stable in the TOP assay and thus represent new dead-end products that need to be added to the list of target analytes for the TOP assay. In contrast, the polyfluorinated ether acids were oxidized during the TOP assay. ADONA formed a 4-carbon PFECA as a new dead-end products, and we are in the process of identifying additional reaction products by high-resolution mass spectrometry. To assess whether sulfate radicals play an important role in the TOP assay, which is conducted under conditions that favor hydroxyl radical formation, we will compare TOP assay results (hydroxyl plus some sulfate radicals) to results obtained with UV/H2O2 oxidation (hydroxyl radicals only). The results of this study are expected to provide an enhanced TOP assay that will capture a larger fraction of oxidizable precursors that may be present in environmental samples.

Enhancing the total oxidizable precursor assay for environmental samples containing per- and polyfluoroalkyl ether acids

2019 Spring National Meeting

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