Department of Chemistry and Center for Nanotechnology, CYCU (Chung Yuan Christian University), 200 Chung Pei Road, Chung-Li 320, Taiwan.
Anal Chim Acta. 2012 Oct 9;746:123-33. doi: 10.1016/j.aca.2012.08.034. Epub 2012 Aug 28.
Several imidazolium-based ionic liquids (ILs) with varying cation alkyl chain length (C(4)-C(10)) and anion type (tetrafluoroborate (BF(4)), hexafluorophosphate (PF(6)) and bis(trifluoromethylsulfonyl)imide (Tf(2)N)) were used as reaction media in the microwave polymerization of methacrylate-based stationary phases. Scanning electron micrographs and backpressures of poly(butyl methacrylate-ethylene dimethacrylate) (poly(BMA-EDMA)) monoliths synthesized in the presence of these ionic liquids demonstrated that porosity and permeability decreased when cation alkyl chain length and anion hydrophobicity were increased. Performance of these monoliths was assessed for their ability to separate parabens by capillary electrochromatography (CEC). Intra-batch precision (n=3 columns) for retention time and peak area ranged was 0.80-1.13% and 3.71-4.58%, respectively. In addition, a good repeatability of RSD(Retention time)=<0.30% and 1.0%, RSD(Peak area)=<1.30% and <4.3%, and RSD(Efficiency)=<0.6% and <11.5% for intra-day and inter-day, respectively exemplify monolith performance reliability for poly(BMA-EDMA) fabricated using 1-hexyl-3-methylimidazolium tetrafluoroborate ([C(6)mim][BF(4)]) porogen. This monolith was also tested for its potential in nanoLC to separate protein digests in gradient mode. ILs as porogens also fabricated different alkyl methacrylate (AMA) (C4-C18) monoliths. Furthermore, employing binary IL porogen mixture such as 1-butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF(4)]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(4)mim][Tf(2)N]) successfully decreased the denseness of the monolith, than when using [C(4)mim][Tf(2)N] IL alone, enabling a chromatographic run to be performed with 1:1 ratio produced baseline separation for the analytes. The combination of ILs and microwave irradiation made polymer synthesis very fast (10min), entirely green (organic solvent-free) and energy saving process.
几种不同阳离子烷基链长度（C(4)-C(10)）和阴离子类型（四氟硼酸盐(BF(4)）、六氟磷酸盐(PF(6)）和双(三氟甲烷磺酰基)亚胺(Tf(2)N）的基于咪唑啉的离子液体（ILs）被用作在微波聚合甲基丙烯酸酯基固定相时的反应介质。在这些离子液体存在下合成的聚（甲基丙烯酸丁酯-乙二甲基丙烯酸酯）（poly(BMA-EDMA)）整体柱的扫描电子显微镜照片和背压表明，当阳离子烷基链长度和阴离子疏水性增加时，多孔性和渗透性降低。通过毛细管电色谱法（CEC）评估这些整体柱分离对羟基苯甲酸酯的性能。保留时间和峰面积的批内精度（n=3 根柱）范围分别为 0.80-1.13%和 3.71-4.58%。此外，日内和日间 RSD(Retention time)（保留时间）<0.30%和1.0%，RSD(Peak area)（峰面积）<1.30%和<4.3%，RSD(Efficiency)（效率）<0.6%和<11.5%的良好重复性说明了使用 1-己基-3-甲基咪唑四氟硼酸盐([C(6)mim][BF(4)])引发剂制备的 poly(BMA-EDMA)整体柱的可靠性。该整体柱还在梯度模式下用于纳米 LC 分离蛋白质消化物的潜力进行了测试。离子液体作为致孔剂还制备了不同的烷基甲基丙烯酸酯（AMA）（C4-C18）整体柱。此外，采用二元 IL 致孔剂混合物，如 1-丁基-3-甲基咪唑四氟硼酸盐([C(4)mim][BF(4)])和 1-丁基-3-甲基咪唑双（三氟甲烷磺酰基）亚胺([C(4)mim][Tf(2)N])，成功降低了整体柱的密度，比单独使用 [C(4)mim][Tf(2)N]IL 时更低，使得在 1:1 比例下进行色谱运行能够产生基线分离的分析物。离子液体和微波辐射的结合使聚合反应非常快速（10min），完全绿色（无有机溶剂）和节能过程。
