Analysis of zwitterionic, cationic, and anionic fluoroalkylated surfactants in sediments by liquid chromatography polarity-switching electrospray ionization coupled to Orbitrap mass spectrometry
Résumé
The environmental prevalence of poly- and perfluoroalkyl substances (PFASs) in aquatic environments has been well documented. To date, perfluoroalkyl acids (PFAAs) such as perfluoroalkyl carboxylates (PFCAs) and sulfonates (PFSAs) have garnered the most attention of PFAS monitoring surveys. However, recent reports indicate that a considerable portion of the total organic fluorine in environmental samples may be attributed to PFAA precursors and other unknown PFASs. Here, we describe a screening strategy for the identification and quantification of a wide range of PFASs in sediments. A total of 28 model PFAS analytes were selected for optimization and validation purposes, including 21 legacy PFASs and 7 novel cationic and zwitterionic PFASs. Instrumental analysis was conducted by ultra-high performance liquid chromatography coupled to a Q-Exactive Orbitrap through a polarity-switching ionization source, allowing simultaneous acquisition of negative and positive mode PFAS within a single run. The extraction/purification step was optimized to maintain a common preparation procedure for all PFASs at once, and adequate whole method recoveries were obtained (60–110 % for 28/28 model PFASs). Method validation included assessment of blank contamination, linearity, detection limits, matrix effects, recovery, accuracy and precision. The newly-developed method was subsequently applied to a selection of riverine or lacustrine sediment samples collected at large spatial scale in mainland France covering the six French Water Basins. In addition to the 28 model PFASs used for optimization and validation purposes, these samples were screened for more than 60 infrequently reported anionic, zwitterionic or cationic PFASs. Perfluorooctane sulfonate (PFOS) generally prevailed over other PFAAs (concentration range of PFOS: 0.084–23 ng g-1 dry weight). Fluorotelomer sulfonamide amines (FTAs) and fluorotelomer sulfonamide betaines (FTABs) were also particularly prevalent in these samples. Hot spots of zwitterionic/cationic PFAS (estimated ΣPFAS+ = 8.9–27 ng g-1 dry weight) were associated with low-flow watercourses in the close vicinity of airports, suggesting the existence of firefighting activities at these sites involving aqueous film forming foam (AFFF) formulations. In the long run, FTAs and FTABs could degrade to more environmentally persistent PFASs such as PFAAs.