Highly Sensitive Detection of Carbohydrates Using Metal Oxide-Modified Electrodes

1.电极表面的氧化铜（CuO）是碳水化合物在强碱性条件下催化氧化所必需的。在该催化反应中，高度氧化的Cu （III）和酸解醇酸基团之间形成醇酸盐，以及醇酸盐向Cu （III）的配合物内电子转移起重要作用。在目前的催化氧化过程中，葡萄糖通过12电子转移被氧化成甲酸盐。氧化铜是碳水化合物多电子氧化的有效催化剂，这意味着氧化铜修饰电极可以作为恒电位安培法下碳水化合物的高灵敏度检测装置，其中不会观察到Au和Pt电极的电催化活性的吸附抑制。为了制备高活性的铜修饰电极，研究了几种铜电极表面氧化的预处理方法。(1)：经过彻底抛光的金属铜电极不具有碳水化合物氧化的活性；(2)：铜的电化学氧化使电极表面形成网状裂纹结构，形成氧化铜，经轻微抛光后微结构仍有一定保留；(3)：轻度空气氧化的稍微再抛光的电极在100个C箭头足够活跃和平滑的氧化铜形成，这是适合于一个流动检测器。空气氧化铜电极在高效液相色谱中对葡萄糖的检测灵敏度低至100 fmol，是直接检测碳水化合物的最佳灵敏度。电极具有1个月以上的长时间稳定性，催化活性无明显下降。未来需要解决的问题是：(1)阐明氧化铜催化的微观反应过程，(2)氧化铜修饰电极的微观结构表征，(3)改进对原糖苷类化合物的高灵敏度检测，(4)改进对同样在氧化铜电极上氧化的胺存在的碳水化合物的选择性检测。少

1.Copper oxide (CuO) on electrode surface has been found to be essential for catalytic oxidation of carbohydrates under strongly alkaline conditions. In this catalytic reaction, alkoxide formation between highly oxidized Cu (III) and acid-dissociated alcolate groups and the intra-complex electron transfer from alcolate to Cu (III) play important roles. During the present catalytic oxidation, glucose for example is oxidized into formate via 12-electron transfer. The fact that copper oxide is such effective catalyst for multiple electron oxidation of carbohydrates means that CuO modified electrodes can be expected as devices for highly sensitive detection of carbohydrate under constant potential amperometry, in which adsorptive inhibition of electrocatalytic activity encountered for Au and Pt electrodes will not observed.2.In order to fabricate highly active CuO-modified electrode, several pretreatments for the surface oxidation of Cu electrode have been examined, which has revealed the … More followings. (1) : thoroughly polished metallic Cu electrode is inactive for carbohydrate oxidation, (2) : electrochemical oxidation of Cu results in the formation of a reticulated cracked structure over the electrode surface, in which copper oxide formation occurs, and the micro-structure remains to some extent by slight polishing, and (3) : mild air-oxidation of the slightly repolished electrode at 100ﾟC arrows sufficiently active and smooth copper oxide formation, which is suitable for a flow-through detector.3.The air-oxidized Cu electrode arrows highly sensitive detection down to 100 fmole as glucose in HPLC,which is the best sensitivity as direct detection of carbohydrates. The electrode has long-time stability over 1 month without significant decrease in the catalytic activity.4.Problems to be solved in future would be (1) : to elucidate microscopic reaction process catalyzed by copper oxide, (2) : characterization of the micro-structure of copper oxide-modified electrodes, (3) : improvement for highly sensitive detection of origosaccarides, and (4) : improvement for selective detection of carbohydrate in the presence of amines which are also oxidized at copper oxide electrodes. Less