Ionic liquid coating for stir bar sorptive extraction and its application for extraction and nontargeted screening analysis via TD-GC–Orbitrap-HRMS of pollutants in river water

In this study, a novel imidazolium-based ionic liquid (IL) coating was developed for stir bar sorptive extraction (SBSE) using a sol-gel method. The effects of different counterions, conditioning temperatures and polymer compositions were investigated. The stir bar with bis((trifluoromethyl)sulfonyl) amide 1-butyl-3-(3-(triethoxysilyl)propyl)-1H-imidazol-3-ium showed good mechanical and thermal stability with high resistance to water solubilization. The extraction efficiency of the IL-coated stir bar was evaluated on a mixture of 11 compounds presenting a wide range of polarities (log K_o/w values between 0.65 and 7.21) using thermodesorption gas chromatography coupled with Orbitrap high-resolution mass spectrometry (TD-GC-Orbitrap-HRMS). The results showed that extraction yields were increased for the IL-stir bar. In contrast, the commercial polydimethylsiloxane (PDMS) stir bar resulted in decreased yields with salt addition, particularly for compounds with log K_o/w > 4. SBSE of contaminants was performed on natural waters collected from France, followed by nontargeted analysis using TD-GC-Orbitrap-HRMS. The results revealed the detection of over 1,000 compounds, with 334 compounds annotated after deconvolution. The IL-stir bar with the addition of NaCl specifically extracted five times more compounds (167 compounds) than did the commercial PDMS stir bar (29 compounds) and more than 10 times more with the addition of NaCl with the PDMS stir bar (15 compounds). Various pollutants, including pesticides, personal care products, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), were identified. The annotations of the identified compounds were classified according to a level of confidence based on comparisons of retention indices, match library spectra and high-resolution mass filters.