Sample injection in microchip‐based capillary zone electrophoresis (CZE) frequently rely on the use of electric fields which can introduce differences in the injected volume for the various analytes depending on their electrophoretic mobilities and molecular diffusivities. While such injection biases may be minimized by employing hydrodynamic flows during the injection process, this approach typically requires excellent dynamic control over the pressure gradients applied within a microfluidic network. The current article describes a microchip device that offers this needed control by generating pressure gradients on‐chip via electrokinetic means to minimize the dead volume in the system. In order to realize the desired pressure‐generation capability, an electric field was applied across two channel segments of different depths to produce a mismatch in the electroosmotic flow rate at their junction. The resulting pressure‐driven flow was then utilized to introduce sample zones into a CZE channel with minimal injection bias. The reported injection strategy allowed the introduction of narrow sample plugs with spatial standard deviations down to about 45 μm. This injection technique was later integrated to a capillary zone electrophoresis process for analyzing amino acid samples yielding separation resolutions of about 4–6 for the analyte peaks in a 3 cm long analysis channel.

中文翻译：

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使用芯片上产生的压力梯度减少样品注入偏差

基于微芯片的毛细管区带电泳 (CZE) 中的样品注入通常依赖于电场的使用，这可能会根据其电泳迁移率和分子扩散率对各种分析物引入不同的注入体积。虽然可以通过在注入过程中采用流体动力流来最小化这种注入偏差，但这种方法通常需要对施加在微流体网络内的压力梯度进行出色的动态控制。当前的文章描述了一种微芯片设备，该设备通过电动方式在芯片上产生压力梯度来提供所需的控制，以最大限度地减少系统中的死体积。为了实现所需的压力产生能力，在两个不同深度的通道段上施加电场，以在它们的连接处产生电渗流速不匹配。然后利用由此产生的压力驱动流将样品区引入 CZE 通道，并具有最小的注入偏差。报告的注射策略允许引入空间标准偏差低至约 45 μm 的窄样品塞。这种进样技术后来被集成到用于分析氨基酸样品的毛细管区带电泳过程中，在 3 cm 长的分析通道中，分析物峰的分离分辨率约为 4-6。报告的注射策略允许引入空间标准偏差低至约 45 μm 的窄样品塞。这种进样技术后来被集成到用于分析氨基酸样品的毛细管区带电泳过程中，在 3 cm 长的分析通道中，分析物峰的分离分辨率约为 4-6。报告的注射策略允许引入空间标准偏差低至约 45 μm 的窄样品塞。这种进样技术后来被集成到用于分析氨基酸样品的毛细管区带电泳过程中，在 3 cm 长的分析通道中，分析物峰的分离分辨率约为 4-6。