Gong Maojun, Wehmeyer Kenneth R, Stalcup Apryll M, Limbach Patrick A, Heineman William R
Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221-0172, USA.
Electrophoresis. 2007 May;28(10):1564-71. doi: 10.1002/elps.200600616.
The electrokinetically pinched method is the most commonly used mode for sample injection in microchip capillary electrophoresis (microCE) due to its simplicity and well-defined sample volume. However, the limited injection volume and the electrophoretic bias of the pinched injection may limit its universal usage to specific applications. Several hydrodynamic injection methods in microCE have been reported; however, almost all claimed that their methods are bias-free without considering the dispensing bias. To investigate the dispensing bias, a simple hydrodynamic injection was developed in single-T and double-T glass microchips. The sample flow was produced by hydrostatic pressure generated by the liquid level difference between the sample reservoir and the other reservoirs. The reproducibility of peak area and peak area ratio was improved to a significant extent using large-surface reservoirs for the buffer reservoir and the sample waste reservoir to reduce the Laplace pressure effect. Without a voltage applied on the sample solution, the voltage-related sample bias was eliminated. The dispensing bias was analyzed theoretically and studied experimentally. It was demonstrated that the dispensing bias existed and could be reduced significantly by appropriately setting up the voltage configuration and by controlling the appropriate liquid level difference.
由于电动夹断法简单且进样体积明确，它是微芯片毛细管电泳（microCE）中最常用的样品进样模式。然而，有限的进样体积以及夹断进样的电泳偏差可能会限制其在特定应用中的广泛使用。已有报道介绍了几种microCE中的流体动力学进样方法；然而，几乎所有方法都声称其方法无偏差，却未考虑分配偏差。为了研究分配偏差，在单T型和双T型玻璃微芯片中开发了一种简单的流体动力学进样方法。样品流由样品储液器与其他储液器之间的液位差产生的静水压力产生。使用大表面积的储液器作为缓冲储液器和样品废液储液器，以降低拉普拉斯压力效应，峰面积和峰面积比的重现性得到了显著提高。在样品溶液上不施加电压的情况下，消除了与电压相关的样品偏差。对分配偏差进行了理论分析和实验研究。结果表明，分配偏差是存在的，通过适当设置电压配置和控制适当的液位差，可以显著降低分配偏差。
