Nontarget and Suspect Screening of Fluorinated Ionic Liquids and PFAS in European Wastewaters Using Supercritical Fluid Chromatography

Per- and polyfluoroalkyl
substances (PFAS) and fluorinated
ionic
liquids were investigated in municipal effluents from 30 wastewater
treatment plants (WWTPs) across 15 European countries using supercritical
fluid chromatography–high-resolution mass spectrometry (SFC-HRMS)
for nontarget screening. Bis-perfluoroalkyl sulfonimide (bis-FASI)
ionic liquids were detected as bis(trifluoromethanesulfonyl)imide
(NTf2–), two rarely reported homologues
(±2 CF2, namely FSI– and BETI–), and two previously unreported homologues (±1
CF2, namely FTFSI– and FTNTf2–). Bis-FASIs were present in 85% of samples and
were more abundant in effluents from larger WWTPs. The fluorinated
anion PF6–, commonly used in ionic liquids,
was found in all samples (≤3 μg/L). Hexafluoroarsenate
(AsF6–), reported here for the first
time in municipal wastewater, was detected in 32% of samples in eight
countries. PF6– and AsF6– concentrations exceeded those of traditional PFSAs
and PFCAs in 97% of the samples. No removal was detected for perfluorinated
compounds, inorganic anions, and low-fluorinated pharmaceuticals and
pesticides. Low-fluorinated substances were detected in 90% of samples
(>100 ng/L), yet PF6– alone surpassed
the combined concentration of all low-fluorinated substances in 27
out of 30 samples. These results reveal the significance of unconventional
fluorinated substances for the overall fluorine load in wastewater,
highlighting the need to extend monitoring strategies beyond legacy
PFAS.