Voltammetric Behavior of Vitamin B_(12) on Glassy Carbon Electrode and Its Application
Liu Yongming *, Li Guizhi (Chemical College, Yantai University, Yantai 264005)
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 (VB 12 ) on glassy carbon electrode(GCE) was abserved by linear-sweep voltammetry. The potential peak for VB 12 is -0.68 V(vs. Ag/AgCl). The mechanism of the electrode reaction was also discussed. In this system VB 12 on GCE was irreversible process with adsorbability. On the conditions of low VB 12 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 VB 12 in the range of 5×10 -9 ～ 5×10 -8 mol/L was obtained. This method has been applied to the direct determination of VB 12 in tablets with satisfactory results.