Determination of total reducible organofluorine in PFAS-impacted aqueous samples based on hydrated electron defluorination

Per-and polyfluoroalkyl substances (PFASs) is a large group of thousands of anthropogenic chemicals. Recently, measurement of total organic fluorine (TOF) to reflect the total PFASs has been recommended in limits and advisories. In this study, a total reducible organofluorine (TROF) assay is developed based on hydrated electron (e(aq)(-)) conversion of PFASs into inorganic fluorine combined with ion chromatograph, which is a common and widespread instrument. The e(aq)(-) is generated in UV/sulfite system with alkaline condition, and the concentration of TROF (C-F_TROF) is the difference of fluoride concentration before and after assay. Method validation uses perfluorooctanesulfonic acid, perfluorooctanoic acid and their main alternatives, and F- recoveries are 76.6%-101%, except for perfluorobutanesulfonic acid (48.5%). Method application of TROF assay uses industrial surfactant products and fluorochemical industry-contaminated water, meanwhile, target PFAS analysis and total oxidizable precursors (TOP) assay are concurrently conducted. Concentrations of PFASs detected in target analysis and TOP assay were converted to fluorine equivalents concentrations (C-F_Target and C-F_TOP). sigma C-F_Target and sigma C-F_TOP account for 0.80%-36% of C-F_TROF in industrial samples, 0.12%-54% in environmental water and 9.7%-14% in wastewater. The TROF assay can be used to initially judge whether PFASs contamination occurred near a hotspot with known sources. The C-F_TROF could infer the extent of PFAS contamination in PFAS-impacted samples and estimate the fraction of uncharacterized PFAS.

Automated summary

In this study, a total reducible organofluorine (TROF) assay based on hydrated electron conversion of PFASs into inorganic fluorine was developed using ion chromatograph. The method can be used to initially judge PFASs contamination and estimate the extent of contamination and the fraction of uncharacterized PFASs.