Determination of total oxidizable precursors in foam surfactants and foam contaminated water based on UV-activated persulfate oxidation

In this study, ultraviolet (UV)-activated persulfate under alkaline condition was developed as an alternative Total Oxidizable Precursor (TOP) assay to convert per- and polyfluoroalkyl substances (PFASs) precursors into detectable peifluoroalkyl acids (PFAAs). The conventional heat-based TOP assay takes 6 h at 85 degrees C, which is time consuming and may lose the volatile PFASs. Shorter time treatment would be beneficial to promote the analysis efficiency of the samples. We here report the UV-based TOP method as faster replacement of conventional heat-based TOP assay. The 6:2 fluorotelomer sulfonate (FTS), 8:2 FTS, and perfluorooctanesulfonamide (FOSA) achieved nearly complete conversion (with the molar yield of PFAAs of 97.2%-109.9%) at 60 min. This new UV-based TOP assay was then applied to 23 industry samples, and the results are comparable with the heat based TOP assay. The perfluoroalkyl carboxylic acids (PECAs) concentrations of 23 samples before and after normal TOP assay were 0-4290 mg L-1 and 438-77,420 mg L-1, respectively. The PFCAs after 60 min UV-based TOP assay was 310-81,881 mg L-1. The Quotient(Mol) of 21 samples were 0.71-1.28, the Quotient(Mol) of other two samples were 1.45 and 1.68, this probably clue W the loss of volatile precursors during heat-based TOP assay. The UV-based TOP assay is an effluent, reliable and faster alternative to the conventional heat-based TOP assay. (C) 2020 Elsevier B.V. All tights reserved.

Automated summary

A new UV-activated persulfate method was developed as a faster alternative to the traditional heat-based TOP assay to convert PFASs precursors into detectable PFAAs. The UV-based TOP assay showed nearly complete conversion of FTS and FOSA within 60 minutes, with comparable results to the heat-based assay in industry samples. The UV-based TOP assay is efficient, reliable and faster than the conventional heat-based method.