Department of Chemical Science and Technology, University of Udine, Udine, Italy.
Electrophoresis. 2010 Aug;31(15):2541-7. doi: 10.1002/elps.201000089.
A simple hydrodynamic injection method is proposed here for microchip CE coupled to electrochemical detection. It is based on the use of a precise syringe pump to push the sample into the microfluidic circuit, accompanied by the application of a secondary electric field to the injection channel, soon after the end of the injection step. In such a way, any counter pressure effect taking place when the sample plug enters the micrometric channel is prevented. Suitable optimization of this secondary electric field enables pushing of sample excess to be avoided and a narrow sample plug during the separation step to be maintained. Best conditions for hydrodynamic injection were achieved injecting catechol as model analyte by pressure with a syringe pump set at a flow rate of 8 microL/min for 6 s and applying to the injection channel a secondary high voltage of 700 V soon after the injection was completed. The reliability of this injection procedure has been proved by comparing electropherograms found for samples containing either catechol alone or catechol and dopamine together with those recorded under the same conditions by electrokinetic injection. Repeatability, expressed as RSD and estimated for seven replicate injections, turned out to be 2.1% for peak height of catechol used as single analyte and 0.9 and 1.1% for catechol and dopamine respectively, simultaneously injected.
这里提出了一种用于微芯片 CE 与电化学检测耦合的简单流体动力学注入方法。它基于使用精密注射器泵将样品推入微流控回路，并在注入步骤结束后不久，对注入通道施加二次电场。通过这种方式，可以防止当样品塞进入微通道时发生任何反压效应。通过适当优化这种二次电场，可以避免推注多余的样品，并在分离步骤中保持狭窄的样品塞。以 8 μL/min 的流速用注射器泵以压力注入儿茶酚作为模型分析物 6 s，并在注入完成后不久向注入通道施加 700 V 的二次高压，是实现水力注射最佳条件的方法。通过将仅含有儿茶酚的样品与在相同条件下通过电动注入记录的样品的电泳图谱进行比较，证明了这种注入程序的可靠性。以儿茶酚的峰高表示的重复性，用七个重复注入进行估计，对于单独使用儿茶酚作为单一分析物的重复注入，结果为 2.1%，同时注入儿茶酚和多巴胺的重复性分别为 0.9%和 1.1%。
