Wätzig H, Lloyd D K
Department of Oncology, McGill University, Montreal, PQ, Canada.
Electrophoresis. 1995 Jan;16(1):57-63. doi: 10.1002/elps.1150160112.
Plasma samples can be analyzed with direct injection onto a capillary electrophoresis system if interactions between the plasma proteins and capillary walls are minimized. This can be achieved using micellar electrokinetic capillary chromatography with a surfactant such as sodium dodecyl sulfate. The surfactant complexes with the proteins, giving them a net negative charge, and thus causes them to be repelled from the negatively-charged fused-silica capillary walls. Migrating as anions, the complexed proteins appear late in the electropherogram. In such analyses, it is important to manipulate the mobility of the analyte(s) of interest such that they migrate in the useful analytical time window before the plasma proteins. In this article, a study of the effect of buffer pH and surfactant concentration on the width of the migration time window is reported. It is shown that at pH 6 the migration time window is wide, but reduced electroosmosis can result in inordinately long run times; pH 7 gives an acceptable analytical window with acceptable run times over a wide range of sodium dodecyl sulfate (SDS) concentrations; pH 8 and higher are most useful when higher concentrations of surfactant (> 50 mM SDS) are employed.
如果血浆蛋白与毛细管壁之间的相互作用降至最低，血浆样品可直接进样到毛细管电泳系统中进行分析。这可以通过使用含有表面活性剂（如十二烷基硫酸钠）的胶束电动毛细管色谱法来实现。表面活性剂与蛋白质形成复合物，赋予它们净负电荷，从而使它们被带负电荷的熔融石英毛细管壁排斥。作为阴离子迁移，复合蛋白质在电泳图中出现较晚。在这类分析中，重要的是控制目标分析物的迁移率，使其在血浆蛋白之前的有效分析时间窗口内迁移。本文报道了一项关于缓冲液pH值和表面活性剂浓度对迁移时间窗口宽度影响的研究。结果表明，在pH 6时迁移时间窗口较宽，但电渗降低会导致运行时间过长；在pH 7时，在较宽的十二烷基硫酸钠（SDS）浓度范围内，可得到可接受的分析窗口和运行时间；当使用较高浓度的表面活性剂（>50 mM SDS）时，pH 8及更高的pH值最为有用。
