Characterization of Nine Isomers in Commercial Samples of Perfluoroethylcyclohexanesulfonate and of Some Minor Components Including PFOS Isomers

Abstract

Electrochemical fluorination of 4-ethylbenzenesulfonyl halides produces a mixture of compounds that has found extensive use as an erosion inhibitor in aircraft hydraulic fluids. This paper reports a study of the composition of commercial samples of this material from two industrial scale manufacturers in terms of the structures and relative concentrations of their components, the major of which is perfluoroethylcyclohexanesulfonate (PFECHS). Fractionation of one of these mixtures by column chromatography produced fractions in which all significant components were of sufficient purity to allow assignment of their structures by F NMR spectroscopy. Assessment of the relevant signals in theF NMR spectra of the commercial mixtures by integration revealed the presence of 14 constituents at levels ≥0.5% in terms of molar contributions. Ten of these involve five pairs of geometric isomers, including cis- and trans-PFECHS which accounted for between 55% and 60% of the components present. Three constituents were determined to be isomers of perfluorooctanesulfonate (PFOS), two branched and the other linear PFOS itself. The availability of samples of the various components also allowed us to identify the compounds responsible for the peaks observed when the commercial samples were analyzed by LC/MS using either C or perfluorophenyl stationary phases.

Target and nontarget screening of PFAS in drinking water for a large-scale survey of urban and rural communities in Québec, Canada

“…Perfluoroethyl cyclohexane sulfonate (PFECHS), a cyclic PFAS found to bioaccumulate in aquatic ecosystems (Wang et al 2016), was detected in 32% of tap water samples from the present survey with a maximum of 7.1 ng/L. Chromatographic peak shapes and MS/MS evidence (Figures S1-S2) suggest that closely eluting PFECHS isomers were also present (Stefanac et al 2018). Two additional cyclic PFAS, perfluoromethyl cyclohexane sulfonate (PFMeCHS) and perfluoromethyl cyclopentane sulfonate (PFMeCPeS), were detected in about 12-14% of tap water samples at sub ng/L levels.…”

Nontargeted Discovery of Novel Contaminants in the Great Lakes Region: A Comparison of Fish Fillets and Fish Consumers

“…PFECHS isomers may be branched isomers present in PFECHS commercial blends that accumulated in human body from other sources. For example, Stefanac et al 35 has characterized nine commercial isomers of PFECHS. The presence of the linear FOSA (CAS No.…”

Per- and polyfluoroalkyl substances in water and wastewater: A critical review of their global occurrence and distribution

“…The US Air Force has identified approximately 200 installations in the USA where PFAS-containing AFFFs have been used. Furthermore, a cyclic perfluorinated acid (PFA) such as perfluoroethylcyclohexanesulfonate (PFECHS), was used as an erosion inhibitor in aircraft hydraulic fluids, which is as recalcitrant to environmental degradation as aliphatic PFAS ( Stefanac et al, 2018 ). In 2011, PFECHS was reported for the first time in predatory fish (<Method Detection Limit (MDL) to 3.7 ng g −1 wet weight in whole-body homogenate) in the Great Lakes, and surface waters of the lake (0.16–5.7 ng L −1 ) ( Silva et al, 2011 ).…”