Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Canada.
Anal Chem. 2012 Mar 20;84(6):2968-73. doi: 10.1021/ac300188s. Epub 2012 Mar 9.
Temperature gradient focusing (TGF) is a counterflow gradient focusing technique, which utilizes a temperature gradient across a microchannel or capillary to separate analytes. With an appropriate buffer, the temperature gradient creates a gradient in both the electric field and electrophoretic velocity. Combined with a bulk counter flow, ionic species concentrate at a unique point where the total velocity sums to zero and separate from each other. Scanning TGF uses varying bulk flow so that a large number of analytes that have large differences in electrophoretic mobility can be sequentially focused and passed by a single detection point. Up to now, scanning TGF examples have been performed using a linear temperature gradient which has limitations in improving peak capacity and resolution at the same time. In this work, we develop a bilinear temperature gradient along the separation channel that improves both peak capacity and separation resolution simultaneously. The temperature profile along the channel consists of a very sharp gradient used to preconcentrate the sample followed by a shallow gradient that increases separation resolution. A specialized design is developed for the heaters to achieve the bilinear profile using both analytical and numerical modeling. The heaters are integrated onto a hybrid PDMS/glass chip fabricated using conventional sputtering and soft-lithography techniques. Separation performance is characterized by separating several different dyes and amino acids that have close electrophoretic mobilities. Experiments show a dramatic improvement in peak capacity and resolution in comparison to the standard linear temperature gradient.
温度梯度聚焦（TGF）是一种逆流梯度聚焦技术，利用微通道或毛细管中的温度梯度来分离分析物。使用适当的缓冲液，温度梯度会在电场和电泳速度中产生梯度。结合体相逆流，离子物质在总速度为零的独特点浓缩，并彼此分离。扫描 TGF 采用变化的体相流速，使得具有大的电泳迁移率差异的大量分析物可以顺序聚焦并通过单个检测点。到目前为止，已经使用线性温度梯度进行了扫描 TGF 示例，但该方法在同时提高峰容量和分辨率方面存在局限性。在这项工作中，我们沿着分离通道开发了双线性温度梯度，可同时提高峰容量和分离分辨率。通道沿线的温度分布包括一个非常陡峭的梯度，用于预浓缩样品，然后是一个较浅的梯度，可提高分离分辨率。使用分析和数值建模为加热器开发了专门的设计，以实现双线性曲线。加热器集成到使用传统溅射和软光刻技术制造的混合 PDMS/玻璃芯片上。通过分离几种具有相近电泳迁移率的不同染料和氨基酸来表征分离性能。实验结果表明，与标准线性温度梯度相比，峰容量和分辨率有了显著提高。
