Simultaneous stripping detection of Zn(II), Cd(II) and Pb(II) using a bimetallic Hg–Bi/single-walled carbon nanotubes composite electrode

A new, sensitive platform for the simultaneous electrochemical assay of Zn(II), Cd(II) and Pb(II) in aqueous solution has been developed. The platform is based on a new bimetallic Hg–Bi/single-walled carbon nanotubes (SWNTs) composite modified glassy carbon electrode (GCE), demonstrating remarkably improved performance for the anodic stripping assay of Zn(II), Cd(II) and Pb(II). The synergistic effect of Hg and Bi as well as the enlarged, activated surface and good electrical conductivity of SWNTs on GCE contribute to the enhanced activity of the proposed electrode. The analytical curves for Zn(II), Cd(II) an Pb(II) cover two linear ranges varying from 0.5 to 11 μg L−1 and 10 to 130 μg L−1 with correlation coefficients higher than 0.992. The limits of detection for Zn(II) and Cd(II) are lower than 2 μg L−1 (S/N = 3). For Pb(II), moreover, there is another lower, linear range from 5 to 1100 ng L−1 with a coefficient of 0.987 and a detection limit of 0.12 ng L−1. By using the standard addition method, Zn(II), Cd(II) and Pb(II) ions in river samples were successfully determined. These results suggest that the proposed method can be applied as a simple, efficient alternative for the simultaneous monitoring of heavy metals in water samples. In addition, this method demonstrates the powerful application of carbon nanotubes in electrochemical analysis of heavy metals.