Dielectric barrier discharge ionization procures characteristic adducts of polyfluoroalkyl substances (PFAS) amenable by gas chromatography-mass spectrometry

Abstract

Fluorotelomer alcohols (FTOHs) and acrylates (FTACs) have been reported as precursors of perfluoroalkyl acids and are known to contaminate biotic and abiotic compartments. Here, a detailed study was carried out for assessing the capability of dielectric barrier discharge ionization (DBDI) to be used as soft ionization technique, as alternative to the more energetic electron ionization (EI), for the quantitative determination of four FTOHs and two FTACs in environmental, biological or food samples by gas chromatography-mass spectrometry. While gas chromatography-EI-mass spectrometry (GC-EI-MS) shows significant fragmentation of the compounds, the ionization obtained by gas chromatography-DBDI-high resolution mass spectrometry (GC-DBDI-HRMS) affords dominant molecular adducts on the spectra. In the positive ion mode, the ion [M + H3O]+ and, of lower intensity, [M + H]+ are observed in the spectra of FTOHs, while the ion [M + H]+ is the most abundant in the spectra of FTACs and accompanied by a lower signal attributed to the ion [M + NO]+. In the negative ion mode, the FTOHs give rise to carbon dioxide and oxygen adducts observed with ions [M − H + CO2]- and [M + O2]-. Structure assignments were confirmed with stable isotope-labelled FTOH analogs and 13CO2. Gas chromatographic separation of the six compounds reveals room for development of methods applicable to soils, plants, water, food and biological materials.