Mercury-free simultaneous determination of cadmium and lead at a glassy carbon electrode modified with multi-wall carbon nanotubes

A multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE) was described for the simultaneous determination of trace levels of cadmium and lead by anodic stripping voltammetry (ASV). In pH 4.5 NaAc-HAc buffer containing 0.02 mol/l KI, Cd2+ and Pb2+ first adsorb onto the surface of a MWNT film coated GCE and then reduce at -1.20 V. During the positive potential sweep, reduced cadmium and lead were oxidized, and two well-defined stripping peaks appeared at -0.88 and -0.62 V. Compared with a bare GCE, a MWNT film coated GCE greatly improves the sensitivity of determining cadmium and lead. Low concentration of I- significantly enhances the stripping peak currents since it induces Cd2+ and Pb2+ to adsorb at the electrode surface. The striping peak currents change linearly with the concentration of Cd2+ from 2.5x10-8 to 1x10-5 mol/l and with that of Pb2+ from 2x10-8 to 1x10-5 mol/l. The lowest detectable concentrations of Cd2+ and Pb2+ are estimated to be 6x10-9 and 4x10-9 mol/l, respectively. The high sensitivity, selectivity, and stability of this MWNT film coated electrode demonstrated its practical application for a simple, rapid and economical determination of trace levels of Cd2+ and Pb2+ in water samples