Kohlheyer Dietrich, Eijkel Jan C T, Schlautmann Stefan, van den Berg Albert, Schasfoort Richard B M
MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands.
Anal Chem. 2008 Jun 1;80(11):4111-8. doi: 10.1021/ac800275c. Epub 2008 Apr 25.
In order to ensure a stable and efficient separation in microfluidic free-flow electrophoresis (FFE) devices, various methods and chips have been presented until now. A major concern hereby is the generation of gas bubbles caused by electrolysis and the resulting disturbances in the position of the separated analyte lanes. Instable lane positions would lead to a decreased resolution in sample collection over time which certainly would be problematic when incorporating a stationary detector system. In contrast to our previous publications, in which we implemented laborious semipermeable membranes to keep bubbles outside the separation region, here we describe an electrochemical approach to suppress the electrolysis of water molecules and therefore bubble formation. This approach allowed a simpler and additionally a closed chip device with integrated platinum electrodes. With the use of this chip, the successful separation of three fluorescent compounds was demonstrated. Quinhydrone, which is a complex of hydroquinone and p-benzoquinone, was added only to the local flow streams along the electrodes, preventing mixing with the separation media and sample. The electrical current was generated via the oxidization and reduction of hydroquinone and p-benzoquinone up to a certain limit of the electrical current without gas formation. The separation stability was investigated for the chip with and without quinhydrone, and the results clearly indicated the improvement. In contrast to the device operating without quinhydrone, a 2.5-fold increase in resolution was achieved. Furthermore, separation was demonstrated within tens of milliseconds. This chemical approach with its high miniaturization possibilities offers an interesting alternative, in particular for low-current miniaturized FFE systems, in which large and open electrode reservoirs are not tolerable.
为了确保微流控自由流电泳（FFE）设备中实现稳定高效的分离，到目前为止已经提出了各种方法和芯片。在此，一个主要问题是电解产生的气泡以及由此导致的分离分析物泳道位置的干扰。不稳定的泳道位置会导致随着时间推移样品收集分辨率降低，当采用固定检测系统时这肯定会成为问题。与我们之前的出版物不同，在之前的出版物中我们采用了费力的半透膜来将气泡阻挡在分离区域之外，在此我们描述一种电化学方法来抑制水分子的电解，从而抑制气泡形成。这种方法使得芯片设备更简单，并且是带有集成铂电极的封闭式芯片。使用这种芯片，成功实现了三种荧光化合物的分离。对苯二酚，它是对苯二酚和对苯醌的复合物，仅添加到沿电极的局部流动流中，防止与分离介质和样品混合。通过对苯二酚和对苯醌的氧化和还原产生电流，直至达到一定电流极限且不产生气体。研究了有和没有对苯二酚时芯片的分离稳定性，结果清楚地表明了性能的提升。与不使用对苯二酚运行的设备相比，分辨率提高了2.5倍。此外，在几十毫秒内就实现了分离。这种具有高度微型化可能性的化学方法提供了一种有趣的替代方案，特别是对于低电流微型FFE系统，在这种系统中不能容忍大的开放式电极储液器。
