Electroanalysis of Dopamine at Methionine Modified Carbon Paste Electrode by Cyclic Voltammetric Technique

The methionine modified carbon paste electrode exhibited good electrocatalytic properties towards dopamine (DA) oxidation in phosphate buffer (pH 7.0) than that of the bare electrode. The electrocatalytic response was evaluated by cyclic voltammetric technique. methionine modified carbon paste electrode has negative charge on its surface and in neutral solution DA exists as the positively charged species. In cyclic voltammetric measurements, favorable ionic interaction (i.e., electrostatic attraction) between DA and Methionine modified carbon paste electrode causes a negative shift of the oxidation potential for DA compared to that at the bare electrode. The electrode response was not affected by the oxidized product of DA. Several parameters such as scan rate variation, DA concentration and pH effect were investigated by cyclic voltammetric measurements. The peak currents were proportional to the concentration of DA with a detection limit of 1×10–6 M.