Polyfluorinated Amides as a Historical PFCA Source by Electrochemical Fluorination of Alkyl Sulfonyl Fluorides

Abstract

Polyfluorinated amides (PFAMs) are a class of compounds produced as byproducts of polyfluorinated sulfonamide synthesis by electrochemical fluorination (ECF). We measured four PFAM derivatives of perfluorooctanoic acid (PFOA) in a wide range of compounds, experimental materials, and commercial products synthesized by ECF. Initial screening was performed using headspace solid phase microextraction gas chromatography mass spectrometry (SPME-GC-MS), and quantification using in-house synthesized standards was accomplished with GC-MS using positive chemical ionization. Two monosubstituted PFAMs, N-methylperfluorooctanamide (MeFOA) and N-ethylperfluorooctanamide (EtFOA), were detected in the majority of materials that were analyzed. Two disubstituted PFAMs, N-methyl-N-(2-hydroxyethyl)perfluorooctanamide (MeFOAE) and N-ethyl-N-(2-hydroxyethyl)perfluorooctanamide (EtFOAE), were not detected in any sample, likely because they were never synthesized. The concentrations of PFAMs in the sulfonamide compounds under study ranged from 12 to 6736 μg/g, suggesting their historical importance as PFCA precursors. In each case, branched isomers for PFAMs were detected, providing further support for their link to an ECF source. A hydrolysis study performed at pH 8.5 showed no degradation of EtFOA to PFOA after 8 days due to the stability of the amide bond. The environmental fate of PFAMs is suggested to be volatilization to the atmosphere followed by oxidation by hydroxyl radical with a predicted lifetime of 3-20 days. Subsequent PFAM exposure to biota will likely lead to enzymatic hydrolysis of the amide linkage to give a PFCA. Human exposure to PFAMs may have contributed to the presence of branched PFOA isomers in blood by serving as an indirect source. The decline in PFOA concentrations in human blood is consistent with a significant drop in PFAM production concurrent with the POSF phase-out in 2000-2001.

Identification of Novel Fluorinated Surfactants in Aqueous Film Forming Foams and Commercial Surfactant Concentrates

“…Recently, polyfluorinated amides have been reported to occur in perfluoroalkane sulfonamido substances as byproducts of ECF synthesis . In the FTICR-MS spectrum of Foam 12, a series of ions was observed corresponding to A , which is an amide version of T , with n = 4, 5, 6, and 7.…”

“…In ESI+, loss of ethene follows loss of the amine oxide, which is analogous to losses of Recently, polyfluorinated amides have been reported to occur in perfluoroalkane sulfonamido substances as byproducts of ECF synthesis. 50 In the FTICR-MS spectrum of Foam 12, a series of ions was observed corresponding to A, which is an amide version of T, with n = 4, 5, 6, and 7. An ion corresponding to C7 A was observed in the base fraction and the FTICR-MS spectrum of Foam 2.…”

Repeated measurements of per- and polyfluoroalkyl substances (PFASs) from 1979 to 2007 in males from Northern Norway: Assessing time trends, compound correlations and relations to age/birth cohort

“…Further, the stable ratio and correlation between PFOS and PFOA during 1979-2007 suggest that their exposure pathways have changed little or done so concomitantly during this period. One hypothesis, which has been proposed to explain the concurrent decrease in serum concentrations of PFOA and PFOS in cross-sectional studies in other countries, states that consumer products made a significant contribution to the total exposure (direct or through degradation of precursors) to these compounds prior to year 2000 (D'eon and Mabury, 2011; Jackson and Mabury, 2012;Olsen et al, 2008;Vestergren and Cousins, 2009). As their production ceased during 2000-2002 human serum concentrations of PFOA and PFOS might be expected to converge as diet-linked environmental pathways would become increasingly important in a post ban situation (Vestergren and Cousins, 2009).…”

Fluorinated Precursor Compounds in Sediments as a Source of Perfluorinated Alkyl Acids (PFAA) to Biota

“…Long chained PFAA (number of carbon atoms [C] ≥ eight for PFCA, and C ≥ six for PFSA) have higher potentials for bioaccumulation than shorter homologues and have been globally detected in organisms. , In addition, uptake and metabolization of precursor compounds has been suggested to be a source of PFAA to organisms. , Historically, large amounts of perfluorooctane sulfonyl fluoride (POSF) has been used as the starting material for the production of the eight-carbon PFSA, perfluorooctanesulfonic acid (PFOS; ) and PFOS precursor compounds including N -alkyl substituted perfluorooctane sulphonamides with eight perfluorinated C (, for simplicity termed preFOS throughout this work), and potential parent compounds: mono-, di-, and trisubstituted phosphate esters of N -ethyl perfluorooctane sulfonamido ethanol (SAmPAPs). − PreFOS and SAmPAPs were used in food contact paper and packaging from the 1970s. , Commercial SAmPAP formulations were dominated by the disubstituted SAmPAP (SAmPAP diester; ), and the presence of this compound has been investigated in a few previous studies. ,, PreFOS have a sulfonyl group, the same perfluorinated moiety as PFOS, and have the potential to be degraded to PFOS if the amine group is replaced with a hydroxy group. PFOS was reported to have higher trophic magnification factors (TMF) compared to other long chained PFAA in several studies, − and transformation of the large amount of preFOS to PFOS has been suggested to be the main mechanism behind this . Some preFOS are neutral at environmentally relevant pH, which combined with their larger size, makes them less water-soluble compared to the anionic PFOS, , and thus more prone to reside in environmental compartments other than water.…”

“…29,31,32 PreFOS have a sulfonyl group, the same perfluorinated moiety as PFOS, and have the potential to be degraded to PFOS if the amine group is replaced with a hydroxy group. PFOS was reported to have higher trophic magnification factors (TMF) compared to other long chained PFAA in several studies, 33−35 and transformation of the large amount of preFOS 36 to PFOS has been suggested to be the main mechanism behind this. 33 Some preFOS are neutral at environmentally relevant pH, which combined with their larger size, makes them less water-soluble compared to the anionic PFOS, 37,38 and thus more prone to reside in environmental compartments other than water.…”