Identifying Unknown Fluorine-Containing Compounds in Environmental Samples Using ¹⁹F NMR and Spectral Database...

The ubiquity of per- and polyfluorinated alkyl substances (PFAS) in the environment is a continuing concern. While typical analytical methods for the analysis of PFAS include both targeted and non-targeted mass spectrometry, there remains a significant portion of fluorinated compounds that are not accounted for by these routine methods. It has been previously demonstrated that ¹⁹F NMR can be used to identify these compounds, helping to close the mass balance on total fluorine in the environment. ¹⁹F NMR offers an unbiased method of analysis that requires no anticipation of fluorine-carbon bonds or functional groups. However, there is resistance to further uptake of NMR spectroscopy as an analytical tool, owing to perceived difficulties in sensitivity and spectral overlap. In this study, we measure the ¹⁹F NMR spectrum of hundreds of fluorinated compounds and use this constructed database to determine the concentration of PFAS in an extracted sample of a known aqueous firefighting foam-contaminated site. The ¹⁹F NMR database has been included for use by other researchers, and we discuss the intricacies of ¹⁹F NMR as applied to environmental samples.