Comprehensive per-and polyfluoroalkyl substances (PFAS) screening in Dutch surface waters using target, suspect, and non-targeted approaches

Per- and polyfluoroalkyl substances (PFAS) form a large chemical group, but routine monitoring targets only a few well-known compounds such as perfluorooctane sulfonic acid (PFOS). To better understand the widespread occurrence of PFAS in Dutch surface waters, we performed target analysis using an expanded list of compounds, combined with extensive suspect and de novo non-target screening (SNTS) to explore unreported PFAS beyond the scope of conventional monitoring. Analyses were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-trapped ion-mobility time-of-flight mass spectrometry (LC-timsTOF-MS). Target analysis focused on 24 previously underreported sulfonamide-based PFASs, enabled by newly available analytical standards and 34 common PFASs, representing 58 compounds. Several N-alkyl perfluoroalkane sulfonamidoacetic acids, including MeFBSAA (up to 50 ng/L), were found. SPr-FHxSA (N-sulfo propyl perfluorohexane sulfonamide), associated with aqueous film-forming foams (AFFFs), was detected in five samples (0.14-1.99 ng/L). In total, 38 PFAS were identified by target analysis. Collision cross-section (CCS) values of analytical standards were measured prior to SNTS. In SNTS, nineteen compounds, mainly fluorinated pharmaceuticals and pesticides, were identified at confidence level 2a using the MassBank library. Another 22 candidates were tentatively classified at levels 2b or 3, including an unsaturated PFOS analogue and a fluazinam transformation product, highlighting the ability of de novo SNTS to uncover unexpected PFAS. Finally, 6:2 fluorotelomer sulfonyl propanoamido-dimethylethyl sulfonate (6:2 FtSO₂AoS) was confirmed at level 1a. Overall, integrating new PFAS standards with SNTS provided a far more complete view of PFAS presence in Dutch waters than target monitoring.