Simultaneous determination of trace Cd(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetry using a reduced graphene oxide-chitosan/poly-l-lysine nanocomposite modified glassy carbon electrode

The reduced graphene oxide (RGO) and Chitosan (CS) hybrid matrix RGO-CS were coated onto the glassy carbon electrode (GCE) surface, then, poly-l-lysine films (PLL) were prepared by electropolymerization with cyclic voltammetry (CV) method to prepare RGO-CS/PLL modified glassy carbon electrode (RGO-CS/PLL/GCE) for the simultaneous electrochemical determination of heavy metal ions Cd(II), Pb(II) and Cu(II). Combining the advantageous features of RGO and CS, RGO and CS are used together because the positively charged CS can interact with the negatively changed RGO to prevent their aggregation. Furthermore, CS has many amino groups along its macromolecular chains and possessed strongly reactive with metal ions. Moreover, PLL modified electrodes have good stability, excellent permselectivity, more active sites and strong adherence to electrode surface, which enhanced electrocatalytic activity. The RGO-CS/PLL/GCE was characterized voltammetrically using redox couples (Fe(CN)63−/4−), complemented with electrochemical impedance spectroscopy (EIS). Differential pulse anodic stripping voltammetry (DPASV) has been used for the detection of Cd(II), Pb(II) and Cu(II). The detection limit of RGO-CS/PLL/GCE toward Cd(II), Pb(II) and Cu(II) is 0.01 μg L−1, 0.02 μg L−1 and 0.02 μg L−1, respectively. The electrochemical parameters that exert influence on deposition and stripping of metal ions, such as supporting electrolytes, pH value, deposition potential, and deposition time, were carefully studied.