Martin, D., G. Munoz, S. Mejia-Avendano, S.V. Duy, Y. Yao, K. Volchek, C.E. Brown, J. Liu, and S. Sauve. Talanta 195:533-542(2019)

The total oxidizable precursor (TOP) assay has potential utility for integrating precursors to perfluoroalkyl acids (pre-PFAAs) into the assessment of sites contaminated by per- and polyfluoroalkyl substances (PFASs). Current research gaps include risks of instrumental matrix effects due to the complexity of post-oxidation extracts, potential reproducibility issues during TOP itself, and limited information for zwitterionic and cationic pre-PFAAs. Investigation of a suitable method for the analysis of groundwater samples using liquid chromatography high-resolution mass spectrometry revealed that initial sample pretreatment through filtration could affect the dissolved PFAS concentrations. Amending the post-oxidation samples with methanol allowed for improved precision and low instrumental matrix effects. Documentation of the oxidation yields of 23 anionic, neutral, zwitterionic, and cationic precursor compounds of PFAAs indicated that these precursor compounds were amenable to TOP conversion. In application, summed PFAS concentrations as high as 5 mg/L were reported before oxidation, and post-oxidation increases of PFCAs up to +2300% were observed.