Lead determination by anodic stripping voltammetry using a p-phenylenediamine modified carbon paste electrode

Carbon paste electrodes were modified by mixing appropriate amounts of the monomers o-phenylendiamine, p-phenylendiamine and m-phenylendiamine (o-PD, p-PD and m-PD) into a graphite powder-paraffin oil matrix. The electropolymerization of the incorporated phenylendiamine was then carried out in a carbon paste electrode in acidic medium by cyclic voltammetry between - 0.30 V and + 0.90 or under constant potential. The modified carbon paste electrodes (MCPEs) obtained by this electropolymerization method were found to be useful for trace determination of Pb2+ in aqueous solutions. Lead(II) was first preconcentrated on the modified electrodes by complexation with the modifier, and the electrode was then transferred to an electrochemical cell. ne best results in terms of sensitivity and detection limit were obtained with poly p-phenylenediamine (poly (p-PD)). For a 10-min preconcentration time, the calibration plot was linear from 5 x 10(-8) mol L-1 to 10(-5) mol L-1, with r(2) = 0.999 and relative standard deviation equal to 5%. However, the lowest lead concentration that could be detected was 10(-9) mol L-1. Interference from metal ions like Cd(II), Hg(II), Zn(II), Fe(II) and Cu(II) was also studied.