Electrochemical detection of lead using overoxidized polypyrrole films

An electrochemical method for the determination of lead has been developed using overoxidized polypyrrole (OPPy) electrode doped with 2(2-pyridylazo)chromotropic acid anion (PACh^2-). The PACh^2- acts both as a chelating agent and a counter anion within the polypyrrole matrix. In a typical assay, Pb²⁺ is accumulated on a solid electrode via the formation of a lead-PACh complex at open circuit. The electrode containing the Pb²⁺PACh^2- is then transferred to a 0.1 M acetate buffer where it is subjected to differential pulse anodic stripping voltammetry. The resulting stripping peak current was linearly related to the concentration of lead. The method has been optimized with respect to pH, concentration of chelating agent, accumulation time, reduction potential and time. The detection limit was found to be 10 ng ml^-1 with a linear range of 0-200 ng ml^-1. The method has been validated for the determination of lead using spiked potable water at 25 ng ml^-1. The average recovery was 93.4% with a relative standard deviation of 8.54%.