Fabrication and Optimization of Electrochemical Detector for HPLC by Use of Microhole Array Electrodes

微孔阵列电极，它可以通过电化学蚀刻的碳纤维-环氧树脂复合材料制成，被用作电化学检测器的HPLC或流动注射分析。对流动池的制造和优化进行了研究。与嵌入在环氧树脂圆盘板中的微孔阵列电极相结合的市售流动池的检查显示，对于六氰合铁酸盐离子获得了与流速无关的稳态电流响应，这表明如果扩散系数值已知，则可以从电流值直接测定分析物而无需任何校准曲线。结果表明，该检测器可用于电活性有机物种，如多巴胺等儿茶酚胺。然而，对于长时间使用电池，观察到电流值的逐渐降低。为了提高探测器的灵敏度，尝试了由几十根或十几万根碳纤维组成的微孔阵列电极的制作。结果发现，电位控制蚀刻是优选的均匀蚀刻这些碳纤维恒电流蚀刻。虽然已经得到了刻蚀电极电位、电解时间与微孔深度的关系，但要得到均匀的微孔还需要进一步的研究。使用脉冲伏安法的物种的检测也进行了研究，但它被发现，双层充电电流的总电流的贡献是大的和蚀刻的碳的表面调理必须进行研究。有人还发现，一些酶的微孔阵列电极的固定化使得有可能在流动池中的特定物种的选择性检测。

Microhole array electrodes, which can be fabricated by electrochemical etching of a carbon fiber-epoxy composite, were employed as electrochemical detectors for HPLC or flow injection analysis. Fabrication and optimization of the flow cells were pursued. Examination with a commercially available flow cell in combination with a microhole array electrode embedded in an epoxy disk plate revealed that steady state current responses which are independent of the flow rate are obtained for hexacyanoferrate ions, indicating that direct determination of analyte is possible from the current value without any calibration curves if the diffusion coefficient value is known. It was shown that the detectors can be used for electroactive organic species like catecholamines such as dopamine. However, gradual depression of current values was observed for the use of the cell for a long duration. In order to increase the sensitivity of the detector, fabrication of microhole array electrodes consisting of tens of or a hundred of a thousand carbon fibers was tried. It was found that potential controlled etching is preferable for uniform etching of these carbon fibers to galvanostatic etching. Though a relation between electrode potential for etching, electrolysis time and depth of the microholes has been obtained, further study for getting uniform microholes would be required. Use of pulse voltammetry for the detection of species was also investigated but it was found that contribution of double layer charging current to the total current is large and surface conditioning of the etched carbon must be studied. It was also found that immobilization of some enzyme to the microhole array electrode makes possible a selective detection of specified species in the flow cell.