Innovative LC-MS Approaches for PFAS Detection and Quantification.

Per- and polyfluoroalkyl substances (PFAS) comprise a large group of synthetics perfluorinated aliphatic compounds, with over 3,000 known variations. Often referred to as "forever chemicals," these substances are recognized for their exceptional persistence in the environment. They are categorized as contaminants of concern (CECs) and are frequently produced as byproducts in various industrial processes, raising potential environmental and health concerns. Traditional analytical methods often fall short in addressing the unique challenges posed by PFAS due to their complex chemistry, wide variety, and low concentrations typically encountered in environmental samples. Moreover, the growing regulatory scrutiny surrounding PFAS compounds highlights the urgency for advanced detection methodologies. Regulatory agencies and environmental organizations are increasingly setting stringent limits on PFAS levels, necessitating analytical approaches that can reliably detect low concentrations, often in parts per trillion (ppt). The first part of the dissertation presents the optimization of an advanced method utilizing UHPLC coupled with LEI-NCI-MS for the analysis of PFAS. The adaptability of the LEI interface is highlighted, effectively facilitating the NCI process of the target compounds after chromatographic separation. The investigation examines NCI fragmentations and proposes a series of fragmentation pathways that clarify the mechanisms governing the NCI ionization of PFAS, as well as the processes occurring during ionization. The use of ACN as the sole reagent gas enhances these findings. Through the optimization of the UHPLC-LEI-NCI-MS approach, this research contributes to the understanding of PFAS analysis, focusing on the interactions that occur during NCI ionization. For all samples analyzed, corresponding methyl esters were formed, which can be considered specific ions for PFAS detection and identification. In the second part, preliminary studies investigate the adsorption and desorption mechanisms associated with ion-exchange extraction phases for 18 per- and polyfluoroalkyl substances (PFAS). The solid-phase microextraction (SPME) device equipped with blade geometry coated in HLB-WAX/PAN exhibited superior extraction efficiency for most of the analyzed compounds. However, non-polar PFAS demonstrated reduced extraction rates, attributed to their hydrophobic properties leading to significant adsorption onto sample container surfaces, which interferes with extraction efficiency. Various desorption parameters were optimized to enhance analysis effectiveness. The determination of the extraction time profile indicated that 30 minutes is optimal for effective PFAS extraction, ensuring adequate quantity extraction and improving throughput for environmental analytical applications. The pre-experiment calibration curve achieved a detection limit of 1 ppt for MOI-MS.