Petruczynik Anna
Medical University of Lublin, Department of Inorganic Chemistry, Staszica 6, 20-081 Lublin, Poland.
J Chromatogr Sci. 2012 Apr;50(4):287-93. doi: 10.1093/chromsci/bms004. Epub 2012 Feb 23.
The silica-based stationary phases with favorable physical characteristics are the most popular in liquid chromatography. However, there are several problems with silica-based materials: severe peak tailing in the chromatography of basic compounds, non-reproducibility for the same chemistry columns, and limited pH stability. Ionic liquids (ILs) as mobile phase components can reduce peak tailing by masking residual free silanol groups. The chromatographic behavior of some alkaloids from different classes was studied on C18, phenyl, and pentafluorophenyl columns with different kinds and concentrations of ionic liquids as additives to aqueous mobile phases. Ionic liquids with different alkyl substituents on different cations or with different counterions as eluent additives were investigated. The addition of ionic liquids has great effects on the separation of alkaloids: decrease in band tailing, increase in system efficiency, and improved resolution. The retention, separation selectivity, and sequence of alkaloid elution were different when using eluents containing various ILs. The increase of IL concentration caused an increase in silanol blocking, thus conducted to decrease the interaction between alkaloid cations and free silanol groups, and caused a decrease of alkaloids retention, improvement of peak symmetry, and increase of theoretical plate number in most cases. The effect of ILs on stationary phases with different properties was also examined. The different properties of stationary phases resulted in differences in analyte retention, separation selectivity, peak shape, and system efficiency. The best shape of peaks and the highest theoretical plate number for most investigated alkaloids in mobile phases containing IL was obtained on pentafluorophenyl (PFP) phase.
具有良好物理特性的硅胶基固定相在液相色谱中最为常用。然而，硅胶基材料存在几个问题：碱性化合物色谱分析中严重的峰拖尾现象、相同化学组成的色谱柱重现性差以及pH稳定性有限。离子液体（ILs）作为流动相成分可以通过掩盖残留的游离硅醇基团来减少峰拖尾。在以不同种类和浓度的离子液体作为水相流动相添加剂的C18、苯基和五氟苯基色谱柱上，研究了不同类型生物碱的色谱行为。研究了不同阳离子上具有不同烷基取代基或具有不同抗衡离子的离子液体作为洗脱剂添加剂的情况。离子液体的添加对生物碱的分离有很大影响：峰拖尾减少、系统效率提高以及分离度改善。使用含有不同离子液体的洗脱剂时，生物碱的保留、分离选择性和洗脱顺序各不相同。离子液体浓度的增加导致硅醇封端增加，从而减少了生物碱阳离子与游离硅醇基团之间的相互作用，在大多数情况下导致生物碱保留减少、峰对称性改善以及理论塔板数增加。还研究了离子液体对不同性质固定相的影响。固定相的不同性质导致分析物保留、分离选择性、峰形和系统效率存在差异。在含离子液体的流动相中，对于大多数研究的生物碱，在五氟苯基（PFP）固定相上获得了最佳峰形和最高理论塔板数。
