金电极介质交换-阴极伏安法对抗坏血酸的测定

Cathodic Voltammetric Determination of Ascorbic Acid with Gold Disc Electrode Based on Medium Exchange

提出了一种测定抗坏血酸的新方法。采用金电极作为工作电极，在0．20mol／L的NaOH溶液中，于0．8V电解50s后，改换介质，在含抗坏血酸的试液中反应约10s，再放入0．20mol／L的NaOH溶液中向阴极化方向扫描，可在-0．1V产生灵敏的还原峰，加入抗坏血酸后峰高下降，且下降的幅度与抗坏血酸的质量浓度成正比。抗坏血酸质量浓度在8．0～264mg／L范围内与还原峰电流△/呈良好的线性关系。检出限为3．6mg／L。介质交换法提高了方法的选择性，样品测试中，常见的干扰物质如多巴胺、尿酸等不干扰测定。方法用于血液和饮料中抗坏血酸的测定，结果与国标法相吻合。

A novel method was proposed for the determination of ascorbic acid based on medium exchange. A gold disc electrode used as the working electrode was electrolysed in 0. 20 mol/L NaOH solution at 0. 8 V for 50 s. It was transferred and immersed into a medium containing ascorbic acid for 10 s, and was then transferred back into 0. 20 mol/L NaOH solution for linear sweep voltammetry scanning. The result showed that in the presence of ascorbic acid, the reductive peak current of the electrode at- 0. 10 V（vs SCE） decreased, and the calibration curve showed a good linearity for the concentration of ascorbic acid in the range of 8.0 - 264 mg/L with a detection limit of 3.6 mg/L. The electrochemical behaviour of gold electrode was investigated by X-ray photoelectron spectroscopy. Two lower peaks at 84. 0 and 87.8 eV and two higher peaks at 86.3 and 89.6 eV were observed, respectively, indicating that two species viz. , Au （0） and Au （ Ⅲ ） existed on the surface of gold electrode. The result also indicated that through medium exchange, the selectivity of the method was increased and that some ordinary biological substances, such as dopamine and uric acid did not interfere with the determination of ascorbic acid. The method was applied to the determination of ascorbic acid in human serum and drink, and the results agreed quite well with those obtained by the Spectrophotometric method.