Stability of Per- and Polyfluoroalkyl Substances in Solvents Relevant to Environmental and Toxicological Analysis

Abstract

Per- and polyfluoroalkyl substances (PFASs) are widely used anthropogenic chemicals. For environmental and toxicological analysis, it is important to understand the stability of PFASs, including novel per- and polyfluoroalkyl ether acids (PFEAs), in commonly used solvents. In this study, we investigated the effects of PFAS characteristics, solvent type, water-to-organic solvent ratio, and temperature on the stability of 21 PFASs including 18 PFEAs. None of the studied PFASs showed measurable degradation in deionized water, methanol, or isopropyl alcohol over 30 days; however, nine PFEAs degraded in the polar aprotic solvents acetonitrile, acetone, and dimethyl sulfoxide (DMSO). PFEA degradation followed first-order kinetics, and first-order rate constants increased with increasing temperature and with decreasing water-to-organic solvent ratio. Monoethers with a carboxylic acid functional group adjacent to a tertiary carbon (>CF-COOH) degraded more rapidly than multiethers in which the carboxylic acid moiety was adjacent to repeating −CF2O– groups. In contrast, monoethers with a carboxylic acid moiety adjacent to a secondary carbon (−CF2-COOH) were stable in all tested solvents. Using high-resolution mass spectrometry, we determined that PFEAs with a >CF-COOH group were stoichiometrically decarboxylated in aprotic solvents and formed products with a >CFH group; e.g., hexafluoropropylene oxide-dimer acid (HFPO–DA or GenX), HFPO-trimer acid, and HFPO-tetramer acid were stoichiometrically converted to Fluoroethers E-1, E-2, and E-3, respectively. PFEA degradation results highlight the importance of solvent choice when preparing dosing solutions and performing extractions for environmental and toxicological assessments of PFEAs.

Low-temperature mineralization of perfluorocarboxylic acids

“…S45 and S58). Such reactivity has also been observed as a complication for analytical standards ( 26 , 27 ). We found that when the same PFOA solution in DMSO/H 2 O was subjected to the decarboxylation conditions but in the presence of NaOH (30 equiv), PFOA instead degraded to a mixture of fluoride, trifluoroacetate ions, and carbon-containing by-products (Fig.…”

Extraction and Matrix Cleanup Method for Analyzing Novel Per- and Polyfluoroalkyl Ether Acids and Other Per- and Polyfluoroalkyl Substances in Fruits and Vegetables

“…After spiked standards were allowed to equilibrate with individual food matrices for 12 h, 4 mL of basic methanol was added for extraction, followed by vortexing for 30 s, sonicating for 30 min, and centrifuging at 4000 rpm for 10 min. The 12 h equilibrium time was selected on the basis of previous studies that used overnight or 12 h equilibration times. ,,, No degradation or transformation of the targeted PFAS was expected on the basis of results of a recent study that found no measurable degradation of 21 PFASs in deionized water, methanol, or isopropanol over 30 days . The supernatant was decanted into clean 15 mL polypropylene tubes.…”

“…For example, Liberatore et al found GenX degraded in acetonitrile, acetone, and dimethyl sulfoxide (DMSO) with half-lives between 1 and 5.2 h . A follow-up study found that 9 PFEAs containing either >CF–COOH or repeating −CF 2 O– groups were unstable in polar, aprotic solvents, highlighting the importance of solvent choice for PFEA extractions. The lack of isotopically labeled standards (IS) presents another obstacle in PFEA analysis. , To date, the only isotopically labeled PFEA that is commercially available is 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)- 13 C 3 -propanoic acid (M3HFPO-DA, the isotopically labeled parent acid of GenX).…”

Total Oxidizable Precursors Assay for Pfas in Human Serum

“…Proteins are removed by denaturation during the methanol extraction, while the methanol is removed prior to the TOP assay by evaporation. Methanol was chosen as extraction solvent instead of acetonitrile both to make this evaporation step faster and to be able to measure GenX, that is not stable in acetonitrile (Liberatore et al, 2020;Zhang et al, 2022). Any residual serum related compounds able to scavenge the persulfate have to be oxidized by the use of excess amounts of a suitable oxidant and harsh conditions.…”