Elucidating Unknown Organofluorine in Municipal Wastewater: A Mass Balance Approach including Fluorinated Pharmaceuticals

Previous studies on per- and polyfluoroalkyl substances (PFAS) have indicated large amounts of unidentified organofluorine in municipal wastewater, raising concerns about their environmental impact. Here, a novel multisorbent solid phase extraction method was applied to municipal wastewater samples, followed by liquid chromatography-high-resolution mass spectrometry-based screening and a quantification workflow combining targeted analysis and combustion ion chromatography for fluorine mass balance analysis. Twenty-three highly fluorinated compounds (i.e., perfluoroalkyl acids and precursors) were identified and, apart from trifluoroacetic acid, quantified in the low- to sub-ppt range. In contrast, 30 low-fluorinated substances (i.e., active pharmaceutical ingredients, pesticides, and transformation products, including some previously unreported metabolites) were identified and quantified at concentrations up to 3 orders of magnitude higher. Despite their lower fluorine content (<30% by mass), these pharmaceuticals accounted for 28-42% of the extractable (organo)fluorine (EOF), with sitagliptin, bicalutamide, and celecoxib carboxylic acid being important drivers of the EOF. The inorganic fluoroanions hexafluorophosphate and tetrafluoroborate were coextracted and contributed 7-19% of the EOF. The multisorbent approach also captured polar cationic pharmaceuticals, substantially influencing the EOF composition. These findings highlight the complexity of fluorine mass balance in municipal wastewater and the need for advanced methods to uncover unidentified organofluorine.