Automated direct-immersion solid-phase microextraction using crosslinked polymeric ionic liquid sorbent coatings for the determination of water pollutants by gas chromatography
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Four different crosslinked polymeric ionic liquid (PIL)-based sorbent coatings were evaluated in an automated direct-immersion solid-phase microextraction method (automated DI-SPME) in combination with gas chromatography (GC). The crosslinked PIL coatings were based on vinyl-alkylimidazolium- (ViCnIm-) or vinylbenzyl-alkylimidazolium- (ViBzCnIm-) IL monomers, and di-(vinylimidazolium)dodecane ((ViIm)2C12-) or di-(vinylbenzylimidazolium)dodecane ((ViBzIm)2C12-) dicationic IL crosslinkers. In addition, a PIL-based hybrid coating containing multi-walled carbon nanotubes (MWCNTs) was also studied. The studied PIL coatings were covalently attached to derivatized nitinol wires and mounted onto the Supelco assembly to ensure automation when acting as SPME coatings. Their behavior was evaluated in the determination of a group of water pollutants, after proper optimization. A comparison was carried out with three common commercial SPME fibers. It was observed that those PILs containing a benzyl group in their structures, either in the IL monomer and crosslinker (PIL–1–1) or only in the crosslinker (PIL–0–1), were the most efficient sorbents for the selected analytes. The validation of the overall automated DI-SPME-GC-flame ionization detector (FID) method gave limits of detection down to 135 μg · L−1 for p-cresol when using the PIL–1–1 and down to 270 μg · L−1 when using the PIL–0–1; despite their coating thickness: ~2 and ~5 μm, respectively. Average relative recoveries with waters were of 85 ± 14 % and 87 ± 15 % for PIL–1–1 and PIL–0–1, respectively. Precision values as relative standard deviation were always lower than 4.9 and 7.6 % (spiked level between 10 and 750 μg · L−1, as intra-day precision).
KeywordsIonic liquids Polymeric ionic liquids Multi-walled carbon nanotubes Solid-phase microextraction Coatings Gas chromatography
V.P. thanks the Spanish Ministry of Economy and Competitiveness (MINECO) for the Ramón y Cajal contract with the University of La Laguna (ULL). V.P. also acknowledges MINECO for the Project Ref. MAT2013-43101-R and funding from Fundación CajaCanarias project ref. SPDs-AGUA05. M.J.T.-R. thanks Fundación CajaCanarias for her PhD research fellowship with ULL. J.L.A. acknowledges funding from the Chemical Measurement and Imaging Program at the National Science Foundation (Grant number CHE-1413199). Authors declare no conflict of interest.
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