碳纳米管/壳聚糖复合膜修饰电极测定尿酸的研究

制备了一种碳纳米管/壳聚糖复合膜修饰的玻碳电极，并通过循环伏安法和计时库仑法详细研究了尿酸在复合膜修饰电极上的电化学行为.对诸如支持电解质，溶液pH，富集时间等实验条件进行了优化，结果表明，在pH＝3.95 0.1 mol/L柠檬酸钠盐支持电解质中，尿酸在复合膜修饰电极上具有良好的电化学响应.相对于裸玻碳电极，尿酸的氧化峰电位负移20 mV，峰电流显著提高，锋形更为尖锐，表明复合膜对尿酸的电化学氧化具有一定的催化作用，计时库仑法结果表明尿酸在复合膜修饰电极上为两电子两质子的电子转移过程.尿酸的氧化峰电流与其浓度分别在5.0×10－9～5.0×10－7 mol/L范围内和1.5×10－6～1.0×10－4 mol/L范围内呈良好的线性关系，线性相关系数分别是0.994 7和0.988 4.开路富集120 s后，检出限为5.0×10－9 mol/L.将该复合膜修饰电极应用于人体实际尿样中尿酸的测量，结果令人满意.

Determination of uric acid based on carbon nanotube/chitosan composite film modified electrode

The carbon nanotube (CNT)/chitosan composite film modified electrode on a glassy carbon electrode had been fabricated. The electrochemical behavior of uric acid was studied at the composite film electrode by cyclic voltammetry and chronocoulometry in detail. The experimental conditions such as supporting electrolytes， pH and accumulation time were optimized. Compared with the bare glassy carbon electrode， the oxidation peak current of uric acid increased greatly， with the negative peak potential shift of about 20 mV， which indicated that CNT/chitosan composite film modified electrode had a good catalytic effect to the electrochemical oxidation of uric acid in pH＝3.95， 0.1 mol/L citric acid salt buffer. The electrochemical behavior of uric acid at this composite film electrode was also characterized by chronocoulometry. The results indicated that oxidation of uric acid involves two-proton two-electron transfer process. Cyclic voltammetry experiment results also showed that the oxidative peak current increased linearly with the concentration of uric acid in the range of 5.0×10－9～5.0×10－7 mol/L and 1.5×10－6～1.0×10－4 mol/L， respectively. One regression equation was i(μA)＝0.8524 c(μmol/L)＋0.1879 with a correlation coefficient of 0.994 7 from 5.0×10－9 to 5.0×10－7 mol/L of UA and another regression equation was i(μA)＝0.04285 c(μmol/L)＋1.299 with a correlation coefficient of 0.988 4 at the range of UA concentration of 1.5×10－6～1.0×10－4 mol/L. The detection limit was 5.0×10－9 mol/L(S/N＝3). The high sensitivity and good selectivity of the composite film electrode was demonstrated by its practical application to the determination of uric acid in urine samples.