Electrochemical sensing of lead(II) by differential pulse voltammetry using conductive polypyrrole nanoparticles

An electrochemical sensor for Pb(II) is described that exploits (a) the outstanding adsorption ability of chitosan modified with quaternary ammonium groups (CQAS; cationic) and of lignosulfonate (LSN; anionic), and (b) the good electrical conductivity of polypyrrole nanoparticles (PPy NPs). A glassy carbon electrode (GCE) was modified with PPy NPs and polydopamine, and CQAS and LSN are used as dispersants in PPy. The modified GCE exhibits high selectivity and sensitivity for Pb(II) in the 0.1 to 50 mu M concentration range, with a 55 nM detection limit (3 sigma method). The redox potentials for Pb(II) is around -0.55 V, and the sensor is not interfered by the presence of Hg(II) and Cu(II). The time dependent stability test showed that this sensor can maintain good reproducibility for one month. This sensor was applied to the determination of Pb(II) in wastewater samples.