Department of Chemistry, University of North Carolina, Chapel Hill, NC, USA.
Electrophoresis. 2011 Nov;32(22):3180-7. doi: 10.1002/elps.201100234. Epub 2011 Oct 20.
Sample transport and electrokinetic injection bias are well characterized in capillary electrophoresis and simple microchips, but a thorough understanding of sample transport on devices combining electroosmosis, electrophoresis, and pressure-driven flow is lacking. In this work, we evaluate the effects of electric fields from 0 to 300 V/cm, electrophoretic mobilities from 10(-4) to 10(-6) cm(2)/Vs, and pressure-driven fluid velocities from 50 to 250 μm/s on sample injection in a microfluidic chemical cytometry device. By studying a continuous sample stream, we find that increasing electric field strength and electrophoretic mobility result in improved injection and that COMSOL simulations accurately predict sample transport. The effects of pressure-driven fluid velocity on injection are complex, and relative concentration values lie on a surface defined by pressure-driven flow rates. For high-mobility analytes, this surface is flat, and sample injection is robust despite fluctuations in flow rate. For lower mobility analytes, the surface becomes steeper, and injection depends strongly on pressure-driven flow. These results indicate generally that device design must account for analyte characteristics and specifically that this device is suited to high-mobility analytes. We demonstrate that for a suitable pair of peptides fluctuations in injection volume are correlated; electrokinetic injection bias is minimized; and electrophoretic separation is achieved.
在毛细管电泳和简单的微芯片中，样品传输和电动进样偏压得到了很好的描述，但对于结合电渗流、电泳和压力驱动流动的设备中样品传输的深入理解还很缺乏。在这项工作中，我们评估了电场强度从 0 到 300 V/cm、电泳迁移率从 10(-4) 到 10(-6) cm(2)/Vs 以及压力驱动流体速度从 50 到 250 μm/s 对微流控化学细胞仪设备中样品进样的影响。通过研究连续的样品流，我们发现增加电场强度和电泳迁移率会改善进样效果，并且 COMSOL 模拟能够准确预测样品传输。压力驱动流体速度对进样的影响很复杂，相对浓度值位于由压力驱动流速定义的表面上。对于高迁移率的分析物，该表面是平坦的，尽管流量波动，进样仍然很稳健。对于低迁移率的分析物，该表面变得更加陡峭，进样强烈依赖于压力驱动流动。这些结果表明，一般来说，设备设计必须考虑到分析物的特性，特别是该设备适用于高迁移率的分析物。我们证明，对于一对合适的肽，进样体积的波动是相关的；电动进样偏压最小化；并且实现了电泳分离。
