The study of organofluorine analysis applied to totaloxidizable precursor (TOP) assay to understand perandpolyfluoroalkyl substances (PFASs)

Abstract: Per- and polyfluoroalkyl substances (PFASs) are synthetic chemicals which are used in a wide range of applications such as aqueous film forming foam (AFFF) for firefighting, paint, coating and cosmetics. For almost a decade, PFASs have received worldwide attention because of the ubiquitous detection of PFAS in the environment and their bioaccumulative, persistent and give toxic effects on animals and humans. A number of study have shown many unknown organofluorine present in environmental samples. The total oxidizable precursor (TOP) method is an oxidation method to convert any precursor compounds of PFASs into measurable perfluorinated carboxylic acids (PFCAs) or sulfonic acids (PFSAs). The aims of this project are to evaluate if the use of total oxidizable precursor (TOP) assay may help improve the mass balance analysis between the quantifiable PFASs and extractable organofluorine in samples. In this study, three water samples: landfill leachate water, contaminated groundwater and adiluted Sthamex AFFF with tap water were undergone TOP assay to reveal the present of any unidentified precursor compounds. To obtain the extractable organofluorine and quantifiable PFAS levels in the samples, combustion ion chromatography (CIC) and liquid chromatography – tandem mass spectrometry (LC-MS/MS) were used, respectively. Results suggested the presence of unidentified precursor compounds in the samples with the aid of TOP assay reaction. Although after the oxidative conversion, a large portion of unidentified PFASs compounds were still present in the samples. The quantifiable PFASs in the samples were up to 7 % of the EOF; in other word, there were still around 93 % of unidentified compounds present in the samples. Further development of analytical method for characterization or identification of these unknown PFAS compounds is needed.