Combustion Ionic Chromatography for the analyse of PFAS content: Method development for the new equipment in MOCA analytical platform
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- Per- and polyfluoroalkyl substances (PFAS) represent a vast family of thousands of persistent anthropogenic contaminants with a carbon-fluorine (–CF2– or –CF3) bond conferring an exceptional thermal and chemical stability. Faced with the strict regulatory thresholds imposed by the European Directive (EU) 2020/2184 (0.5 μg/L for total PFAS) and the limitations of targeted LC-MS/MS and other analytical methods, developing global screening workflows is crucial. This thesis investigates the potential of Combustion Ion Chromatography (CIC) to quantify Adsorbable Organic Fluorine (AOF) following a preconcentration step on granulated activated carbon (GAC) and direct liquid sample injection to quantify total fluorine (TF) in aqueous sample. Initially, the Ion Chromatography (IC) detection module was optimized to control background signal and eliminate systemic contamination sources (ultra-pure water quality, technical solutions, and needle-washing protocols). These hardware optimizations yielded excellent detection and quantification limits for fluorides solutions of NaF, giving a LOD = 0.108 ppb and a LOQ = 0.278ppb. Subsequently, the two configurations of the CIC module were evaluated. On one hand, the direct liquid injection CIC method encountered a significant technological limitation: a systematic dilution factor of 58 (100 μL sample recovered in 5.8mL of absorption solution), which reduce the analyte signal intensity. On the other hand, the coupled CIC-AOF method proved to be highly efficient (when using lab produced fluorobenzoic acid solution). By concentration of the initial volume via retention on GAC. It overcomes the dilution barrier, demonstrating a great linearity (R² = 0.999) and very low global performance limits (LOD = 0.197ppb and LOQ = 0.498ppb in fluoride). The method provides enough analytical performance for regulatory monitoring below the 0.5 ppb threshold. In conclusion, this thesis shows that, even after monitoring the new device, the direct liquid injection CIC technique remains limited by the dilution. But regarding the CIC-AOF coupling, it stands out as a highly performing technology, capable of establishing the determination of fluoride (and thereby PFAS) content in water sample in the context of future analyses.