A new multi-residue method for PFAS analysis in wastewater for environmental and public health risk assessment

This work focuses on the detection and quantification of per-/polyfluorinated alkyl substances (PFAS) in influent wastewater, using wastewater-based epidemiology via a new multi-residue ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. This covers a range of PFAS classes including perfluoroalkyl carboxylic acids (e.g. PFHxA), perfluoroalkyl sulfonic acids (e.g. PFBS), precursors (e.g. EtFOSAA), perfluoroalkyl phosphonic (e.g. PFOPA) and phosphinic acids (e.g. PFPiA), and novel PFAS (e.g. Gen X). Weak-anion exchange (WAX) cartridges and hydrophilic-lipophilic balance (HLB) solid-phase extraction cartridges for sample preparation were compared, with higher intensities and recoveries seen for different compounds for both cartridges. Method detection limits ranged from 0.03 (PFBS) to 756.9 ng L⁻¹ (MeFOSA). Average method accuracy was 95% with a precision of 17.9%. Elution solvents on HLB cartridges were tested (MeOH, ACN, and IPA), with MeOH found to work sufficiently for the analytes in this method. Some PFAS were found to adsorb to silanised glassware and HDPE material during sample preparation. The method was applied to influent wastewater samples from the South-West of England across three days to assess daily load and potential population exposure. Daily loads ranged from 1935.4 ± 146.9 (PFNA) to 45,368.9 ± 24,983.6 mg day⁻¹ (8:2 diPAP), and population-normalised daily load ranged from 2.5 ± 0.2 to 55.2 ± 30.4 µg day⁻¹ 1000 inh⁻¹ for those same compounds. Risk from human exposure and acute risk to the environment were assessed and deemed to be low; however, risk can be difficult to assess due to more factors needing to be considered.