화학공학소재연구정보센터
Electrochimica Acta, Vol.50, No.11, 2175-2180, 2005
Voltammetry of Vitamin B-12 on a thin self-assembled monolayer modified electrode
Vitamin B-12 showed three reduction waves at a thin self-assembled monolayer of mercaptoacetic acid modified gold electrode at 0.21, 0.16, -0.41 V in a 0.01 mol l(-1) HCl solution at a scan rate of 100 mV s(-1). The overall electrode reaction followed an ECE mechanism, leading to a total two-electron exchange. The predominant Co(III) form was reduced directly at 0.21 V by a one-electron transfer accomplished by CN- cleavage into the cyanocob(II)alamin. The latter species then equilibrated with the base-off B-12r, which was immediately reduced into B-12s at 0.16 V. The wave at -0.41 V might be a catalytic hydrogen wave. The cathodic peak currents at 0.21 V were controlled by the diffusion of Vitamin B-12. On the base of its diffusion behavior, the semi-derivate voltammetric method for the detection of Vitamin B-12 was presented. The semi-derivate voltammetric peak current of the wave at 0.21 V was linear with the content of Vitamin B-12 in the range of 4.0 x 10(-9) to 4.0 x 10(-5) mol l(-1). The detection limit was 1.0 x 10(-9) mol l(-1). The proposed method was applied successfully to determine the content of Vitamin B-12 in pharmaceutical preparations. (c) 2004 Elsevier Ltd. All rights reserved.