Preparation of Novel Ionic Liquids-Based Sol-Gel Coatings for Solid-Phase Microextraction

Two hydroxylethyl-functionalized ionic liquids (ILs), 1-(2'-hydroxylethyl)-3-methylimidazolium tetrafluoroborate (HEMIM[BF4]) and 1-(2'-hydroxylethyl)-3-methylimidazolium bis-(trifluoromethanesulfonyl)imide (HEMIM[N(SO2CF3)(2)]) were first used as selective stationary phase to prepare ILs-hydroxyl-terminated silicone oil (OH-TSO) hybrid organic-inorganic coatings for solid-phase microextraction (SPME) by sol-gel technology. The underlying mechanism of the sol-gel reactin was proposed and the successful binding of ILs to the sol-gel substrate was confirmed by FT-IR spectra. The performance of these two ILs-based coatings was somewhat different, depending on the type of anions in ILs structure. Firstly, in contrast to HEMIM[N(SO2CF3)(2)]-OH-TSO coating, the pores on the surface of HEMIM[BF4]-OH-TSO coating are arranged more orderly and uniformly with a smaller size. Secondly, the HEMIM[N(SO2CF3)(2)]-based fibers had much higher thermal stability compared with the HEMIM[BF4]-based fibers. Thirdly, the extraction efficiency of HEMIM[BF4]-OH-TSO fiber towards phenolic environmental estrogens and aromatic amines was superior to that of HEMIM[N(SO2CP3)(2)]-OH-TSO fiber, and OH-TSO fiber without ILs. Moreover, these ILs-based SPME fibers had wonderful solvent resistance, wide useable pH range and good coating preparation reproducibility. Efficient analysis of aromatic amines with headspace SPME-GC was achieved using sol-gel-derived HEMIM[N(SO2CF3)(2)]-OH-TSO fiber. The method showed linear response over three to four orders of magnitude. The limits of detection were very low, ranged between 6.3 and 201.3 ng/L. The relative standard deviation values were below 7% and the recovery varied from 87.4% to 111.5%.