PFAS Non-Target Screening
Per- and polyfluorinated alkyl substances (PFASs) are man-made high-performance chemicals comprising thousands of different substances. They have been used or are still used in a multitude of industrial and consumer product applications. Some PFASs such as e.g. perfluorooctane sulfonic acid (PFOS) are regulated today in many countries due to their extreme environmental persistence, bioaccumulation potential and toxicity. However, many of the PFASs produced and used are potential environmental precursors of the highly persistent and problematic substances. The production volumes and use patterns of these potential precursors are usually not known and thus estimates for emission volumes and pathways are lacking or highly uncertain. It is therefore of utmost importance to develop non-target screening techniques to detect and identify PFASs in the environment. In the current project we explore the possibility of using ultra-high resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) to detect highly fluorinated substances in particulate environmental samples. The samples are extracted with methanol and the raw extract is filtered and subsequently measured with direct-infusion FT-ICR-MS, leading to tens of thousands of signals in negative electrospray MS. Based on a PFAS database a set of heuristic rules was developed to assign signals (m/z values) from the full scan ultra-high resolution mass spectra that are likely to belong to highly fluorinated substances. Isotope patterns and fragmentation experiments are finally used to verify molecular formula and to yield further structural information. This is a novel and complementary analytical approach in non-target analysis of highly fluorinated substances.