Cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWAdSV) were used to investigate the performance of an ex situ plated bismuth-film electrode (BiFE) employed to study the electrochemical behavior and the electroanalytical determination of vitamin B-12. Two pH-dependent reversible peaks were observed for the B-12r-B-12s (Co(II)-Co(I)) couple after pre-concentration of vitamin B-12 at -1.2 V for 30s. An adsorption-controlled reaction rate with one electron involved in the electrochemical step was observed for the mechanism implicated. The calibration curve obtained in a Britton-Robinson solution at pH 12.0 was linear in the concentration range of 0.100-1.000 mu mol L-1 (r=0.9980). The detection limit was found to be 33.1 nmol L-1. The electrode was successfully employed for the determination of vitamin B-12 in two pharmaceutical products. The electrode performance was compared with those of modified and unmodified electrodes as well as with the UV-vis spectrophotometric method. (C) 2012 Elsevier Ltd. All rights reserved.