将氧化石墨烯（GO）、多壁碳纳米管（MWNTs）和羧甲基壳聚糖（CMCS）超声混合后滴涂到玻碳电极（GCE）基体上得到修饰电极（MWNTs/GO/CMCS/GCE），采用循环伏安法（CV）考察NO₂^-和L-色氨酸（L-Trp）在修饰电极上的电化学行为。计算得MWNTs/GO/CMCS/GCE的有效面积为3.243 0×10^-6cm²，电极膜表面积明显增加，加速了电子转移，有利于被测物质的吸附和富集。结果表明：NO₂^-（在pH 4.7磷酸盐缓冲溶液中）和L-Trp （在pH 4.0乙酸-乙酸钠缓冲溶液中）在该修饰电极上分别有明显的电催化氧化作用；两者的浓度依次在1.0×10^-7~3.5×10^-1mol·L^-1和1.0×10^-8~2.7×10^-1mol·L^-1内与其相应的氧化峰电流值之间呈线性关系，其检出限（3S/N）依次为1.2×10^-8，5.0×10^-8mol·L^-1。方法用于腐败生菜中NO₂^-含量和模拟样品中L-Trp含量的CV测定，所得测定结果分别与紫外-可见分光光度法和荧光光度法的测定结果相符。

Glassy carbon electrode (GCE) was modified by dropping a suspension of graphene oxide (GO), multi-walled carbon nanotubes (MWNTs) and carboxymethyl chitosan (CMCS) onto its surface to obtain the modified electrode of MWNTs/GO/CMCS/GCE. Electrochemical behaviors of NO₂^- and L-tryptophan (L-Trp) at the modified electrode were studied by cyclic voltammetry (CV). The effective area of the modified electrode was found to be 3.243 0×10^-6cm², which was significantly increased as compared with the bare electrode and thus electron transfer was accelerated and adsorption-enrichment of the analytes was facilitated. As shown by the results, significant electro-catalytic oxidations of NO₂^- (in PBS of pH 4.7) and L-Trp (in acetate buffer of pH 4.0) were observed at the modified electrode separately, and linear relationships between values of the oxidation peak current and the concentration of NO₂^- in the range of 1.0×10^-7 to 3.5×10^-1mol·L^-1 and of L-Trp in the range of 1.0×10^-8 to 2.7×10^-1mol·L^-1 were obtained, with detection limits (3S/N) of 1.2×10^-8mol·L^-1, and 5.0×10^-8mol·L^-1 respectively. NO₂^- in a sample of rotten cos lettuce and L-Trp in a simulated sample were determined by the proposed CV method, giving results in consistency with those found by UV-spectrophotometry (for NO₂^-) and by fluorospectrophotometry (for L-Trp).