Simultaneous Determination of Cadmium and Mercury Using Ion-exchange Voltammetry
YI Hong chao, WU Kang bing, HU Sheng shui * (Department of Chemistry, Wuhan University, Wuhan, 430072)
In this paper, a sodium montmorillonite modified glassy carbon electrode for the simultaneous determination of Cd 2+ and Hg 2+ was described. Cd 2+ and Hg 2+ were firstly preconcentrated on the surface of the sodium montmorillonite modified electrode via ion exhchange interaction, and then reduced. In the following step, reduced cadmium and mercury were stripped by applying voltammetric scanning. The experiment parameters, such as supporting electrolyte and pH values, amount of sodium montmorillonite, accumulation potential and time, and scan rate, were optimized. It was found that the peak currents are linear with the concentration in the range from 8×10 -9 mol/L to 2×10 -6 mol/L of Cd 2+ and from 4×10 -8 mol/L to 7.5×10 -6 mol/L of Hg 2+ . The detect limits are 1×10 -9 mol/L for Cd 2+ and 8×10 -9 mol/L for Hg 2+ . Using this modified electrode, trace levels of Cd 2+ and Hg 2+ in water samples were determined and the results suggested that this modified electrode was effective for the simultaneous determination of Cd 2+ and Hg 2+ .