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

The methionine modified carbon paste electrode exhibited good electrocatalyticproperties towards dopamine (da) oxidation in phosphate buffer (ph 7.0) than that of thebare electrode. the electrocatalytic response was evaluated by cyclic voltammetric technique.methionine modified carbon paste electrode has negative charge on its surface and in neutralsolution da exists as the positively charged species. in cyclic voltammetric measurements,favorable ionic interaction (i.e., electrostatic attraction) between da and methioninemodified carbon paste electrode causes a negative shift of the oxidation potential for dacompared to that at the bare electrode. the electrode response was not affected by theoxidized product of da. several parameters such as scan rate variation, da concentrationand ph effect were investigated by cyclic voltammetric measurements. the peak currentswere proportional to the concentration of da with a detection limit of 1×10–6 m.