ZeroPM removal workshop: Passive sampling for PFAS: Status and applications

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036756. One fits all? – A TOP assay fitness-check for comprehensive PFAS determination Frank Thomas Lange, Karsten Nödler ZeroPM Removal Workshop, Lesvos, Greece October 7, 2025 What is the TOP assay? Total Oxidizable Precursor assay, Proxy for PFAS Total Houtz & Sedlak, 2012 ES&T 46, 9342-9349 .OH radical mediated oxidative digestion S2O8 2- → 2 SO4 -. SO4 -.+ OH-→ SO4 2- + .OH CnF2n+1 S O O NR1 R2 CnF2n+1 R F3CO (CF2)3O CHF CF2C O OCn-1F2n-1 C O OOH . OH . OH . Cn-1F2n-1 C O O-Cn-2F2n-3 C O OCnF2n+1 C O O- +++ ? F3CO (CF2)2C O O- + ... Perfluoroalkyl sulfonamide-based precursors Fluorotelomer-based precursors Polyfluoroalkyl ether-based precursors PFMOPrADONA Δ One comprehensive TOP assay protocol fits all? Comprise all environmental matrices of interest •Drinking water, groundwater, surface water, wastewater •Soil leachates, soil extracts •Soils, sediments, biosolids •(Consumer) products (AFFFs, repellents, textiles, food contact materials, …) •Biota, blood For a complete mass balance, comprise all precursors and products •Non-extractable PFAS residues (precursors) •Volatile PFAS (precursors) •Ultrashort-chain PFAS (products) Review on persulfate-based TOP assay protocols Conversion yields of fluorotelomer precursors 0 20 40 60 80 100 120 140 4:2 FTSA (b) 4:2 FTSA (c) 4:2 FTSA (d) 4:2 FTSA (m) 6:2 FTSA (a) 6:2 FTSA (b) 6:2 FTSA (f) 6:2 FTSA (c) 6:2 FTSA (d) 6:2 FTSA (m) 6:2 FTSA (o) 8:2 FTSA (a) 8:2 FTSA (b) 8:2 FTSA (c) 8:2 FTSA (g) 8:2 FTSA (h) 8:2 FTSA (j) 8:2 FTSA (j) 8:2 FTSA (k) 10:2 FTSA (c) 10:2 FTSA (j) 5:3 acid (c) 7:3 acid (c) 7:3 acid (l) 6:2 FTUCA (c) 6:2 FTUCA (l) 8:2 FTUCA (b) 8:2 FTUCA (c) 10:2 FTUCA (b) 10:2 FTUCA (c) M4* (b) 6:2 FTCA (b) 10:2 FTCA (b) 6:2 FTI (b) 6:2 FTOH (b) 8:2 FTOH (b) 8:2 FTOH (n) 10:2 FTOH (b) 10:2 FTOH (n) 8:2 FTAC (b) 6:2 FTMAC (b) 8:2 FTMAC (b) 10:2 monoPAP (d) 10:2 monoPAP (e) 6:2 diPAP (a) 6:2 diPAP (h) 6:2 diPAP (i) 6:2/8:2 diPAP (d) 6:2/8:2 diPAP (e) 8:2 diPAP (a) 8:2 diPAP (d) 8:2 diPAP (e) 8:2 diPAP (i) 6:2 FTAB (b) 6:2 FTAB (c) molar conversion yields in % TFAA PFPrA PFBA PFPeA PFHxA PFHpA PFOA PFNA PFDA PFUnDA B) 0 Not analysed ultrashortchain PFCAs Loss of volatile PFASs ∑Δ PFCAs (unknown precursors) = ∑ΔPFCAs (measured) – ∑ΔPFCAs (known precursors, calculated) Lange et al., 2024 TrEAC 44, e00242 eTOP vs dTOP protocols, e. g. for soil Lange et al., 2024 TrEAC 44, e00242 Discrimination of •non-oxidizable PFAS •non-extractable PFAS •volatiles •ultrashort-chain PFAAs (TFA, PFPrA) dTOP vs eTOP of a soil sample reveals non-extractable residues (NER) dTOP eTOP Urgent need for standardization! Göckener et al. 2022 Environ. Sci. Eur. 34, 2345 PFOS formation via dTOP assay Perfluoroalkyl sulfonamide-based precursor hydrolysis/oxidation ? (dTOP) aerobic microbial degradation PFOA PFOS Lange 2022, LUBW report “Studie zur Aussagekraft des Total Oxidizable Precursor-Assays (TOP-Assay) … “ Lange et al. 2022, Mitt. Umweltchem. Ökotox. 28. (4) 134–137 NR1 R2 TOP assay of a technical product Liquid product with a side-chain fluorinated acrylate-based polymer for textile coating Analysis of native sample accounts for only 0.02 % of the TOP assay result. eTOP assay analysis of the dried product accounts for only 1.44 % of dTOP assay result. dTOP is needed for polymer digestion! ΣF(PFAS) = 1.18 % Supplier information: 1.2 % 0 10 20 30 Native TOP dTOP µmol/kg TFA PFPrA PFBA PFPeA PFHxA PFHpA Data from Lange et al. 2025, Mitt. Umweltchem. Ökotox. 31/2, 33-37 F F F F F F F F F F F F F Crosslinker to textile Nonfluorinated side chain Polyfluorinated side chain Polyacrylate chain O OO OO OO O F F F F F F F F F F F F F eTOP dTOPNative Experimental setup: irradiation chamber at UVA (365 nm) PFCA yields during PhotoTOP of 6:2 FTSA (10 µg/L) at UVA (365 nm) 0 2 4 6 8 10 12 14 16 18 20 22 5 min 30 min 5 min 30 min concentration in nmol/L TFA PFPrA PFBA PFPeA PFHxA PFHpA 6:2 FTSA unknown/loss 99.6% 94.6% 87.3% 12.9% ultrapure water River Rhine water 5 min: ca. 88 J/m2 30 min: ca. 545 J/m2 Conclusions and perspectives •A perfect generic TOP assay protocol for all matrices and including ultrashort-chain, polymeric, and volatile PFASs does not yet exist. •PhotoTOP as a chemical-free alternative is a very promising technique and should be optimized for routine application. •After optimization standardization of the PhotoTOP assay would help to adopt this approach for legislation. Acknowledgements BWPLUS project FluorTECH, BWPFC19007 (2018-2022) LUBW: TOP assay study (2021-2022) BMBF project PFClean (2023-2026) EU project ZeroPM (2021-2026) and … to all former and present involved colleagues at TZW This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036756.