| Abstract: | In this paper, the possibility of analyzing levodopa and carbidopa by differential pulse voltammetry (DPV) utilizing a glassy carbon electrode in 0.1 mol L?1 HClO4 is reported. Cyclic voltammograms of levodopa show a redox couple with anodic and cathodic peak potentials at 0.58 V and 0.52 V (vs. Ag/AgCl), respectively. For carbidopa, there are two oxidation waves with maximum currents at 0.53 V and 1.02 V, without any cathodic counterpart at slow enough scan rate. Since in such conditions, the oxidation product of carbidopa does not undergo reduction, it is possible to analyze levodopa without interference. On the other hand, carbidopa can be determined between 0.85 V and 1.1 V in the presence of levodopa, coating the electrode with a Nafion film, which is selective for carbidopa. The developed methodology was applied to two different commercial samples of pharmaceutical products. The obtained data were compared with the results of the analysis by high performance liquid chromatography (HPLC) with UV detection, showing good correlation (relative errors changing between 0.4% and 3.5%) and absence of interference of the other components that accompanied the pharmaceuticals. |
