Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China), School of Chemistry & Chemical Engineering of Guangxi Normal University, Yucai Road 15, Guilin 541004, Guangxi, China.
J Chromatogr A. 2009 Dec 18;1216(51):8845-50. doi: 10.1016/j.chroma.2009.10.071. Epub 2009 Nov 1.
A silica-based monolithic stationary phase with mixed-mode of reversed phase (RP) and weak anion-exchange (WAX) for capillary electrochromatography (CEC) has been prepared. The mixed-mode monolithic silica column was prepared using the sol-gel technique and followed by a post-modification with hexadecyltrimethoxysilane (HDTMS) and aminopropyltrimethoxysilane (APTMS). The amino groups on the surface of the stationary phase were used to generate a substantial anodic EOF as well as to provide electrostatic interaction sites for charged compounds at low pH. A cathodic EOF was observed at pH above 7.3 due to the full ionization of residual silanol groups and the suppression in the ionization of amino groups. A variety of analytes were used to evaluate the electrochromatographic characterization and column performance. The monolithic stationary phase exhibited RP chromatographic behavior toward neutral solutes. The model anionic solutes were separated by the mixed-mode mechanism, which comprised RP interaction, WAX, and electrophoresis. Symmetrical peaks can be obtained for basic solutes because positively charged amino groups can effectively minimize the adsorption of positively charged analytes to the stationary phase.
一种基于硅胶的整体固定相，具有反相（RP）和弱阴离子交换（WAX）的混合模式，用于毛细管电色谱（CEC）。混合模式整体硅胶柱是通过溶胶-凝胶技术制备的，然后用十六烷基三甲氧基硅烷（HDTMS）和氨丙基三甲氧基硅烷（APTMS）进行后修饰。固定相表面的氨基基团用于产生大量的阳极电渗流，同时在低 pH 值下为带电化合物提供静电相互作用位点。在 pH 值高于 7.3 时观察到阴极电渗流，这是由于残余硅醇基团的完全电离以及氨基基团的电离抑制。使用各种分析物来评估电色谱特性和柱性能。整体固定相对中性溶质表现出反相色谱行为。模型阴离子溶质通过混合模式机制分离，该机制包括 RP 相互作用、WAX 和电泳。对于碱性溶质可以获得对称峰，因为带正电荷的氨基基团可以有效地最小化带正电荷的分析物对固定相的吸附。
