碳纳米管修饰电极法测定蔬菜中的亚硝酸盐

Preparation of Poly-L-Cys/MWNT Modified Electrodes and Determination of Nitrite in the Vegetables

研究了籼一半胱氨酸／多壁碳纳米管修饰玻碳电极的制备、亚硝酸盐在该修饰电极上的电化争性质，建立了差分脉冲伏安法测定食品中亚硝酸盐的新方法。结果表明在pH4．5的磷酸缓冲溶液中，该纳米修饰电极对NO2-有良好的电催化作用，N02-在电极上的氧化动力学过程为扩散控制过程；亚硝酸盐在该纳米修饰电极上的氧化电流与食品中的亚硝酸盐浓度在5×10-7～2．7×10-5mol／L范围具有良好的线性关系：ipa=0．1355C＋0．1479（R2=0．9％6），最低检测限为（S／N=3）为7×10-3mg／kg。该法用于测定蔬菜样品小油菜和黄瓜中的亚硝酸盐含量，其结果为0．721，0．546mg／kg与国家标准方法测定结果0．698，0．543mg／kg一致，且具有快速、方便的优势，而且所需化学试剂较少。

The poly-L-Cys/MWNT modited electrodes were prepared,-and the Voltarnnaetric behavior of nitrites on the poly- L-Cys/MWNT modified electrode was studied. A novel method for the determination of nitrite in foods by differential pulse voltammetry was established. At pH 4.5 phosphate buffer solution, the modified electrode exhibited good electrocatalytic activity on the oxidation of NO2, and the electrode reaction of NO2 was a diffusion control process. In the optimized conditions, the calibration curves for the determination of nitrite in foods demonstrated an excellent linear response ipa = 0.135 5C＋0.147 9 （RZ=0.996 6） in the range from 5 x 10.7 -2.7× 10.5 mol/L with the detection limit of 7× 10.3 mg/kg （S/N=3）. The proposed method was successfully applied in the simultaneous determination of nitrites in vegetables, these results of 0.721, 0.546 mg/kg respectively agreed with the national standard method of spectrophotometric method （0.698, 0.543 mg/kg） and with vapid, convenient advantages and less requirement of chemical reagent.