Simultaneous determination of cadmium(ii), lead(ii), copper(ii) and mercury(ii) using an electrode modified by N/S co-doped graphene

Abstract

Graphene (RGO), N-doped graphene (NRG) and N/S co-doped graphene (NSRG) were prepared using an improved Hummers’ method and a hydrothermal method. Then, they were used to modify a glassy carbon electrode (GCE) for simultaneous determination of Cd(II), Pb(II), Cu(II) and Hg(II) via the method of square wave anodic stripping voltammetry (SWASV). The comparative study indicates that NSRG/GCE shows the best electrochemical performance among the three graphene modified electrodes. The doping amounts of N and S, deposition potential, stripping frequency and deposition time have significant influence on the detection performance of NSRG/GCE. Under the optimal experimental conditions, NSRG/GCE exhibits good linearity over a wide concentration range from 0.005 to 2.5 μM for Cd(II) and Hg(II), and from 0.005 to 3.0 μM for Pb(II) and Cu(II). During simultaneous determination of Cd(II), Pb(II), Cu(II) and Hg(II), the limits of detection are 6.5 nM, 1.3 nM, 6.0 nM and 16.1 nM (S/N = 3), and the sensitivities are 25.0, 120.7, 102.4 and 36.0 μA μM⁻¹, respectively. Meanwhile, NSRG/GCE has the advantages of high selectivity, great reproducibility and excellent stability. Moreover, successful detection of metal ions in actual seawater samples manifests that NSRG/GCE can be employed in practical applications.