维生素B_(12)在玻碳电极上的伏安行为及测定

Voltammetric Behavior of Vitamin B_(12) on Glassy Carbon Electrode and Its Application

在以 0 .1mol/LKCl为支持电解质、pH 4.5 6的Britton Robinson缓冲溶液中 ,维生素B12 在玻碳电极上于 -0 .68V(vs.Ag/AgCl)处产生灵敏的还原峰 ,该峰的电化学还原反应机理为具有吸附特性的不可逆过程。当VB12 的浓度较低、搅拌吸附时间较长且扫描速度较快时电极反应可完全由吸附态的VB12 所控制 ,在电极上的吸附模式符合Frumkin等温式。VB12 浓度在 5× 1 0 -9～ 5× 1 0 -8mol/L范围内与还原吸附峰电流呈线性关系 ,据此对VB12 样品进行测定 ,取得了较好的结果。

In the mixture of 0.1 mol/L KCl as supporting electrolyte and Britton-Robinson buffer (pH 4.56), a sensitive reduction peak of vitamin B-12(VB12) on glassy carbon electrode(GCE) was abserved by linear-sweep voltammetry. The potential peak for VB12 is - 0.68 V (vs. Ag/AgCl). The mechanism of the electrode reaction was also discussed. In this system VB12 on GCE was irreversible process with adsorbability. On the conditions of low VB12 concentration, quick scanning speed and long adsorption time, the reduction current peak could be totally controlled by adsorption process with Frumkin isotherm model. A linear relationship between the adsorption peak, current and the concentration of VB12 in the range of 5 x 10(-9) similar to 5 x 10(-8) mol/L was obtained. This method has been applied to the direct determination of VB12 in tablets with satisfactory results.