Synthesis of reference standards for emerging sulfonamide PFAS precursors suspected in aqueous film-forming foams via a benzyl intermediate

Abstract

Per- and polyfluoroalkyl substances (PFAS) have been widely studied due to their persistence in the environment and potential risks to wildlife and human health. The identification and analysis of these thousands of compounds in various environmental matrices is crucial for assessing their presence and evaluating potential risks. However, the growing list of suspected PFAS necessitates the synthesis of pure standards, for the development and validation of analytical methods. This study describes the synthesis of ten sulfonamide-based PFAS precursors suspected to be in the environment potentially because of the use of aqueous film forming foams (AFFFs). Starting materials, delivered as isomer mixtures were purified by recrystallization using a benzylamine intermediate as a protecting group. The targeted compounds were obtained by alkylation of this benzyl intermediate followed by a deprotection step using hydrogen and a palladium catalyst. This method was evaluated on different PFAS classes. The ten synthesized compounds, including N-dimethylamminopropyl perfluoroalkane sulfonamides (AmPr-FASA) and N-trimethylammoniopropyl perfluoroalkane sulfonamides (PFASAmS), N-sulfopropyl perfluorohexane sulfonamide (SPr-FHxSA), N-dimethylaminopropyl perfluorohexane sulfonamidopropylsulfate (AmPr-FHxSAPS), N-perfluorobutane sulfonamide (FBSA) and N-perfluorobutane sulfonamidoethanol (FBSE) were characterized by NMR and HRMS. These reference materials will be valuable for developing and validating analytical methods for emerging PFAS in environmental samples.