Gong Maojun, Wehmeyer Kenneth R, Limbach Patrick A, Heineman William R
Department of Chemistry, University of Cincinnati, PO Box 210172, Cincinnati, OH 45221-0172, USA.
J Chromatogr A. 2007 Oct 12;1167(2):217-24. doi: 10.1016/j.chroma.2007.08.042. Epub 2007 Aug 21.
Flow manipulation in sweeping microchip capillary electrophoresis (CE) is complicated by the free liquid communication between channels at the intersection, especially when the electroosmotic flows are mismatched in the main channel. Sweeping in traditional CE with cationic micelles is an effective way to concentrate anionic analytes. However, it is a challenge to transfer this method onto microchip CE because the dynamic coating process on capillary walls by cationic surfactants is interrupted when the sample solution free of surfactants is introduced into the microchip channels. This situation presents a difficulty in the sample loading, injection and dispensing processes. By adding surfactant at a concentration around the critical micelle concentration and by properly designing the voltage configuration, the flows in a microchip were effectively manipulated and this sweeping method was successfully moved to microchip CE using tetradecyltrimethylammonium bromide (TTAB). The sweeping effect of cationic surfactant in the sample solution was discussed theoretically and studied experimentally in traditional CE. The flows in a microchip were monitored with fluorescence imaging, and the injection and sweeping processes were studied by locating the detection point along the separation channel. A detection enhancement of up to 500-fold was achieved for 5-carboxyfluorescein.
在扫描微芯片毛细管电泳（CE）中，交叉处通道间的自由液体连通会使流动操控变得复杂，尤其是当主通道中的电渗流不匹配时。在传统CE中使用阳离子胶束进行扫描是浓缩阴离子分析物的有效方法。然而，将此方法转移到微芯片CE上具有挑战性，因为当不含表面活性剂的样品溶液引入微芯片通道时，阳离子表面活性剂在毛细管壁上的动态涂层过程会被中断。这种情况在样品加载、进样和分配过程中带来了困难。通过添加浓度接近临界胶束浓度的表面活性剂并合理设计电压配置，微芯片中的流动得到了有效操控，并且使用十四烷基三甲基溴化铵（TTAB）成功地将这种扫描方法转移到了微芯片CE上。理论上讨论了样品溶液中阳离子表面活性剂的扫描效果，并在传统CE中进行了实验研究。用荧光成像监测微芯片中的流动，并通过沿分离通道定位检测点来研究进样和扫描过程。对于5-羧基荧光素，检测增强倍数高达500倍。
