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.