Mémoire, Partim B : Method development for the analysis of halogenated volatile and semi-volatile persistent organic pollutants (chlorinated, brominated, and fluorinated) using GC-APCI-TIMS-TOFMS

Abstract

Volatile and semi-volatile halogenated persistent organic pollutants (POPs) are routinely monitored by gas chromatography coupled to mass spectrometry (GC-MS). However, the reliable identification and quantification of trace-level compounds can remain challenging, notably due to coeluting isomers and isobars. Adding an extra separation dimension by ion mobility spectrometry can improve overall separation performance and provide complementary identification information through collision cross section (CCS) values. The aim of this Master’s thesis was to develop and evaluate a gas chromatography–atmospheric pressure chemical ionization–trapped ion mobility spectrometry-time-of-flight mass spectrometry (GC-APCI-TIMS-TOFMS) workflow for the analysis of halogenated compounds relevant to POP monitoring. In Chapter 1, a targeted GC-APCI-TIMS-TOFMS method was developed for three volatiles per- and polyfluoroalkyl substances (PFAS): perfluorooctyl ethanol, N-methylperfluoro-1-octanesulfonamide, and 2-(N-methylperfluoro-1-octanesulfonamido) ethanol. Instrumental parameters were optimized using a combination of one-factor-at-a-time testing and design of experiments, and fragmentation behavior was investigated under TIMS-off and TIMS-on conditions. A specific analytical issue, namely the broad ion mobility peak observed for N-methylperfluoro-1-octanesulfonamide, was explored and discussed. In Chapter 2, food matrices prepared within the TEQfood project were analysed. Quantification results for emerging brominated and mixed halogenated POPs obtained using GC-APCI-TIMS-TOFMS were compared with those obtained using the reference GC-EI-sector high-resolution mass spectrometry (HRMS) method. While GC-APCI-TIMS-TOFMS enabled congener determination, it showed lower sensitivity for some ultra-trace congeners and tended to overestimate concentrations relative to GC-EI-sector HRMS for a subset of analytes. Finally, Chapter 3 investigated pollutants sorbed on microplastics and macroplastics collected from rivers in Madagascar and from the Sambre River (Belgium), using targeted analysis with chlorinated biphenyl and polybrominated diphenyl ether standards combined with suspect screening to broaden chemical characterization. Overall, this work highlights both the potential and current limitations of GC-APCI-TIMS-TOFMS for halogenated POP analysis and identifies methodological improvements required to extend the approach towards broader PFAS coverage and robust screening workflows.