Simultaneous Determination of Ascorbic Acid and Dopamine at Electropolymerized Manganese(III) 5-[o-(1-imidazole butoxy) phenyl]-10,15,20-triphenylporphrine Chloride Film-modified Glass Carbon Electrode

The electropolymerization of manganese(III) 5-[o-(1-imidazolyl butoxy) phenyl]-10,15,20-tri-phenylporphrine chloride (o-ImBPTPPMn(III)Cl) produces a stable and electrochemically active film from strong acidic aqueous solutions. Cyclic voltammetry was used to study the in situ growth of the poly(o-ImBPTPPMn(III)Cl) films. An electrode was employed to study the electrocatalytic oxidation of ascorbic acid (AA) and dopamine (DA) using cyclic voltammetry. It was found that the oxidation of AA at the surface of the poly(o-ImBPTPPMn(III)Cl) film-modified glass carbon electrode occurs at a potential of about 407 mV, more negative than that of an unmodified glass carbon electrode. Differential pulse voltammograms (DPV) of simultaneous determination of AA and DA exhibited a dynamic linear range of 2.0×10−6−1.0×10−4 M and a detection limit of 1.0 μM for AA, and a corresponding dynamic linear range of 6.5×10−7−2.6×10−5 M and a detection limit of 0.39 μM for DA. In DPV, the poly (o-ImBPTPP Mn(III)Cl) film-modified glass carbon electrode could completely separate the oxidation peak potentials of AA and DA for about 240 mV present in the same buffer solution of 0.1 M phosphate, although at the unmodified glass carbon electrode, the peak potentials were indistinguishable. This modified electrode was quite effective not only in detecting AA and DA separately but also in simultaneously determining the concentration of each component in the mixture, without influencing the results obtained.