Nontargeted Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Environmental Samples Related to Alpine Skiing Using Ion Mobility Filtering and High-Resolution Mass Spectrometry

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a group of commonly used compounds, known particularly for their hydrophobic, nonstick properties. Their unique chemistry has also led to their use in ski waxes. While competition rules and some regions have recently banned the use of fluorinated waxes, the persistence of PFAS means they could still be detected for years. Given the hazards and concern about PFAS contamination, this study investigated if PFAS could be detected at a ski area that supports a high-level race program, where these waxes would have been in use for many years. Samples were collected from a variety of locations within a ski area in New Hampshire, USA, to investigate the levels and trends of PFAS in this type of environment. While previous studies have focused on targeted analysis for known PFAS, this study utilized both targeted and nontargeted analysis with high-resolution mass spectrometry (HRMS) and ion mobility to look for new and unexpected PFAS. In the nontargeted analysis, detected peaks were first compared to an internal HRMS PFAS library for identification, and unknown peaks were selected for further scrutiny based on their detected drift time in the ion mobility dimension. An ion mobility filter was created to look for PFAS based on the unique trendlines of collisional cross section (CCS) vs m/z exhibited by halogenated molecules and applied to the list of detected peaks. Using this filter, a number of homologous series of PFAS were tentatively identified, in addition to those found with suspect screening. Two of the series included dioic perfluorinated acids and monohydrogen-substituted perfluoroalkyl carboxylic acids (H-PFCAs). While authentic standards were not available for many of the tentative identifications, two standards were purchased and compared with experimental data to confirm the proposed structures of shorter chain compounds in these series, thus increasing the evidence that identification of the homologous series in these cases was correct. This preliminary study, based on a limited number of water samples, indicated that PFAS contamination could be detected at the ski area. The inclusion of nontargeted analysis provided a more thorough understanding of the contamination’s extent by identifying new species that would be overlooked using targeted methodologies.