壳聚糖修饰石墨电极半微分伏安法测定L-抗坏血酸

Determination of L-Ascorbic Acid with Semi-differential Voltammetry at Chitosan Modified Graphite Electrode

采用滴涂法制备了壳聚糖修饰石墨圆盘电极，并用于Ｌ－抗坏血酸（ＬＡＡ）的半微分伏安法测定。研究了电解液种类及酸度、膜厚度、富集电位及时间、扫速和温度等因素对伏安曲线的影响，获得了较为优化的测试条件。在０．２０ｍｏｌ／Ｌ ＮａＨ２ＰＯ４－Ｎａ２ＨＰＯ４（ｐＨ６．０）缓冲液中，ＬＡＡ的浓度在 １． ０×１０－５～ ６． ０ × １０－４ ｍｏｌ／Ｌ范围内与氧化峰电流呈良好线性关系（ ｒ＝０．９９９７），检测限达６．７×１０－７ｍｏｌ／Ｌ；生物体内常见的干扰物质如亚硝酸盐、多巴胺、葡萄糖等不干扰测定。 ９次测得电极在含 ５．０ ×１０－５ ｍｏｌ／Ｌ ＬＡＡ试液中峰电流的 ＲＳＤ为３．６％，回收率为９６．４％～１０２．８％（ ｎ＝５）。已成功用于维生素Ｃ片剂和人血清中 ＬＡＡ的测定。

Graphite disc electrode modified with chitosan by drop-coationg method was used to determine L-ascorbic acid (ICA) by semi-differential voltammetry. The effect of the type and acidity of electrolytes, the thickness of chitosan membrane, enrichment potential and time, scan late and temperature on the voltammetric curve of LAA were investigated to acquire optimun conditions.In 0. 20 mol/L NaH2PO4-Na2HPO4-HPO4 buffer (pH 6. 0), there was an excellent linearity between oxidation current and concentration of L-ascorbic acid in the range from 1.0 ×10-6 to 6.0 × 10-4 mol/L (r = 0.9997) with a detection limit of 6. 7 ×10-7 mol/L.Some ordinary biological substances such as nitrite, dopamine,glucose, etc. did not interfere with the determination of LAA. Relative standard deviation (RSD) Of the oxidation peak currents obtained from 9 determinations of the same solution containing 5 .0 ×10-5 LAA was 3.6%. Recoveries of 96.4% -102. 8% were obtained from five determinations. This method has been applied to the determination of LAA in tablets and human serum successfully.