Detection of Perfluoroalkyl Substances in different matrices by Target and Untarget Mass spectrometry techniques

Perfluoroalkyl substances (PFAS) are a large group of synthetic chemicals composed of a chain of linked carbon and fluorine atoms. Because the carbon-fluorine bond is one of the strongest, these substances do not easily degrade in the environment and are therefore known as "forever chemicals”. PFAS are compounds capable of bioaccumulating even at ultra-trace levels. Currently, over 4,700 PFAS compounds have been identified, but most studies have focused on only a small portion of these molecules. Consequently, their health effects are still unknown and the development of targeted and untargeted analytical approaches for new and precise PFAS detection methods is largely required. In this master's thesis, we analyzed different sample extracts using liquid chromatography coupled with QTOF-MS/MS. By employing Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH-MS®) a full-scan acquisition was obtained to perform qualitative and quantitative analysis of 193 PFAS, using 23 mass-labeled internal standards, thus developing a new analytical method for PFAS target screening. The SWATH approach also allows for untargeted screening through the high-resolution Software Molecule Profiler®, which can suggest the most suitable formulas and likely structures from molecular precursors and fragment data. Due to the EU's established regulations that restrict some types of long-chain PFAS and related compounds, new molecules have been synthesized as alternatives, including chloroperfluoropolyether carboxylates (ClPFPECAs), which are associated with numerous health endpoints. This class of new analytes has been included in our screening and has been detected in various plant and animal matrices, together with other congeners whose structure is currently not fully discovered. The developed methods can identify and quantify PFAS of interest with high confidence levels even in samples at concentrations down to 100 ppt , thanks to the sensitivity, selectivity, and specificity of the ZENO-TOF instrument.