Electrochemical Determination of L-dopa in the Presence of Ascorbic Acid by Gold Nanoparticles Functionalized 8-Hydroxyquinoline Modified Glassy Carbon Electrode

A new modified glassy carbon electrode (GCE) was prepared using gold nanoparticles functionalized by 8-HQ. This modified surface was characterized by cyclic voltammetry, differential pulse voltammetry, scanning electron microscopy and FT-Raman spectroscopy. The modified electrode exhibits strong electrocatalytic activity towards the oxidation of a mixture of L-dopa and ascorbic acid (AA) with reduction of over potentials. Simultaneous analysis of this mixture at the conventional bare electrode surface is not feasible. However, two well-resolved oxidation peaks for AA and L-dopa are observed in the modified electrode and can be used for the estimation of AA and L-dopa simultaneously. Simultaneous analysis of AA and L-dopa using the DPV method, shows that the oxidation current is linear with L-dopa concentration in the range of 3.0-10 mu M with a detection limit of about 0.31 mu M (S/N=3). The proposed method was applied for the detection of L-dopa in real samples.