The effect of adding transition metals to the electrolyte containing proton pump inhibitors, such as rabeprazole sodium (RAB sodium), on the voltammetric response of pencil graphite electrode was studied. Both square-wave adsorptive stripping voltammetry (SWAdSV) and cyclic voltammetry (CV) were utilized to elucidate and confirm the possible complexation reaction that could occur between RAB sodium and cobalt as a transition metal. The current signal due to the oxidation process was a function of the concentration of RAB sodium, pH of the medium, cobalt concentration, scan rate, frequency, and deposition time at the electrode surface. This phenomenon could be used for the determination of RAB sodium using CV and SWAdSV. The oxidation peak current linearly varied with the concentration over the range of 0.05–9
109 M and 0.2–8.5
107 M for SWAdSV and CV, respectively. The limits of detection were found to be 0.015
109 M and 0.06
107 M for SWAdSV and CV, respectively. The validity of using these methods for the determination of RAB sodium in its pharmaceutical formulation and human urine samples was evaluated.