Improved Total Oxidizable Precursor Assay for Quantifying Polyfluorinated Compounds Amenable to Oxidative Conversion to Perfluoroalkyl Carboxylic Acids

Abstract

Despite the fact that thousands of perfluoroalkyl and polyfluoroalkyl substances (PFASs) are in widespread commercial use, analytical methods capable of quantifying them in environmental samples are available for less than 100 compounds. The total oxidizable precursor (TOP) assay provides a means of quantifying unknown PFASs by oxidizing PFASs into perfluoroalkyl carboxylates (PFCAs), which are readily measured by liquid chromatography−tandem mass spectrometry. To improve the reproducibility of the TOP assay, [ 13 C 8 ] perfluorooctane sulfonamide was added to samples prior to oxidation as an efficiency indicator and its conversion to [ 13 C 8 ] perfluorooctanoic acid was quantified. The recovery of precursors was also improved by including the analysis of ultrashort PFCAs, namely trifluoroacetic acid and perfluoropropyl carboxylic acid, which revealed the presence of ultrashort precursors. A method for distinguishing between branched and linear PFCAs was also integrated into the assay to enhance its ability to differentiate between PFASs produced by electrochemical fluorination and those produced by fluorotelomerization. In addition to its potential application in forensic studies, the improved TOP assay reduces uncertainties associated with incomplete oxidation of precursors or formation of ultrashort PFCAs that are not detected by standard analysis methods.

New PFASs Identified in AFFF Impacted Groundwater by Passive Sampling and Nontarget Analysis

“…A study on 13 AFFF formulations showed that ultrashort- and short-chain precursors were produced as early as the 1970s . Due to their high mobility and polarity, the ultrashort-chain PFASs are expected to migrate down gradient of source areas more rapidly than their longer-chained counterparts, leading to potential accumulation in water bodies, and consequently, these compounds may be observed in drinking water. − ,, Although some efforts have been made to investigate the removal of ultrashort-chain PFASs, the focus has mainly been on longer-chain PFCAs and PFSAs with guideline advisory or regulatory levels.…”

Sulfonamide Per- and Polyfluoroalkyl Substances Can Impact Microorganisms Used in Aromatic Hydrocarbon and Trichloroethene Bioremediation

“…Besides the identified PFASs in the AFFF, there are other AFFF components that could have contributed to inhibition but were not evaluated in this study. For example, Tsou et al detected untargeted short and ultrashort (less than four perfluorinated carbons) precursors based on an improved total oxidizable precursor (TOP) assay on the AFFF used in this study, 23 the potential toxicity of which is not understood.…”

“…Further, the mechanisms driving inhibition are still unclear, particularly under different redox conditions. We sought to evaluate the potential toxicity of hexafluoroalkyl ECF-based PFASs, which are the most abundant precursors in ECF-based AFFF. , We focused specifically on zwitterionic AmPr-FHxSA and its biotransformation products FHxSA and PFHxS, as well as a 3M AFFF containing high concentrations of AmPr-FHxSA and PFHxS. In particular, we wanted to determine if hexafluoroalkyl PFASs negatively impact microorganisms capable of degrading common PFAS source zone co-contaminants such as benzene, toluene, ethylbenzene, and xylene (BTEX) and TCE.…”

Water Analysis: Emerging Contaminants and Current Issues

“…Source apportionment was the subject of another study by Antell et al, who used the TOP assay to identify PFAS sources, including AFFFs, impacted sites, municipal WWTPs, and municipal solid waste landfills from 46 locations in 3 countries . Including the TOP assay data in principal component analysis (PCA) showed improved separation among sources.…”