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

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 mu M for Cd(ii) and Hg(ii), and from 0.005 to 3.0 mu M 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 mu A mu M-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.