Voltammetric Determination of Dopamine at the Surface of TiO2 Nanoparticles Modified Carbon Paste Electrode

In the present paper, the use of a novel carbon paste electrode modified by N,N'(2,3-dihydroxybenzylidene)-1,4-phenylenediamine (DHBPD) and TiO2 nanoparticles prepared by a simple and rapid method for the determination of dopamine (DA) was described. In the first part of the work, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. A linear segment was found with slope value of about 48 mV/pH in the pH range 2.0 - 12.0. The apparent charge transfer rate constant (k(s)) and transfer coefficient (alpha) for electron transfer between DHBPD and TiO2 nanoparticles-carbon paste electrode were calculated. In the second part of the work, the mediated oxidation of DA at the modified electrode was described. It has been found that under optimum condition in cyclic voltammetry, a high decrease in overpotential occurs for oxidation of DA at the modified electrode. The values of electron transfer coefficients (alpha) and diffusion coefficient (D) were calculated for DA, using electrochemical approaches. Differential pulse voltammetry (DPV) exhibited a linear dynamic range from 0.08 mu M to 20.0 mu M and a detection limit (3 sigma) of 3.14 x 10(-8) M for DA. Finally, this method was used for the determination of DA in DA injection, using standard addition method.