Wallenborg S R, Nyholm L, Lunte C E
Department of Chemistry, University of Kansas, Lawrence 66045, USA.
Anal Chem. 1999 Feb 1;71(3):544-9. doi: 10.1021/ac980737v.
Capillary electrophoresis (CE) was coupled to a micro-electrode-based end-column amperometric detector. The influences of separation voltage, CE buffer concentration, and capillary-to-electrode distance on the observed hydrodynamic voltammetry of dopamine and catechol were studied using a separation capillary with an i.d. of 25 microns. It was found that an increased CE voltage, increased buffer concentration, or decreased capillary-to-electrode distance resulted in a positive shift of the observed half-wave potentials for both dopamine and catechol. At a constant separation current of 1.6 microA, the observed half-wave potential was found to increase with applied separation voltage. Furthermore, when experiments were carried out with a platinum quasi-reference electrode instead of a Ag/AgCl reference electrode, similar shifts in half-wave potential were observed. These results indicate that the observed shifts are an effect of the separation voltage rather than the separation current or a change in the reference potential. The characteristics of end-column detection with and without a fracture decoupler were compared. It was found that the effects of separation voltage, CE buffer concentration, and capillary-to-electrode distance were minimized by the use of a decoupling device. The observed half-wave potentials for dopamine and catechol were more positive when a CE capillary without a decoupler was employed compared to when a decoupler was used. Additionally, using the fracture decoupler, the observed half-wave potentials for both dopamine and catechol were approximately the same as when no CE voltage was applied (i.e., when the hydrodynamic voltammograms were recorded under flow injection conditions).
毛细管电泳（CE）与基于微电极的柱端安培检测器联用。使用内径为25微米的分离毛细管，研究了分离电压、CE缓冲液浓度以及毛细管与电极距离对多巴胺和儿茶酚的流体动力学伏安法的影响。结果发现，增加CE电压、增加缓冲液浓度或减小毛细管与电极距离，都会导致多巴胺和儿茶酚的观察到的半波电位正向偏移。在1.6微安的恒定分离电流下，观察到的半波电位随施加的分离电压增加。此外，当使用铂准参比电极代替Ag/AgCl参比电极进行实验时，也观察到了类似的半波电位偏移。这些结果表明，观察到的偏移是分离电压的影响，而不是分离电流或参比电位变化的影响。比较了有无断裂去耦器时柱端检测的特性。结果发现，使用去耦装置可使分离电压、CE缓冲液浓度和毛细管与电极距离的影响最小化。与使用去耦器时相比，使用无去耦器的CE毛细管时，多巴胺和儿茶酚的观察到的半波电位更正。此外，使用断裂去耦器时，多巴胺和儿茶酚的观察到的半波电位与不施加CE电压时（即在流动注射条件下记录流体动力学伏安图时）大致相同。
