Stripping voltammetry of Pb(II), Cu(II), and Hg(II) at a nafion-coated glassy carbon electrode modified by neutral ionophores

The analysis of Pb2+, Cu2+ and Hg2+ by stripping voltammetry using a Nafion-coated glassy carbon electrode modified with diethyldithiocarbamic acid (DDTC) or 1,4,7,10,13,16-hexaoxacyclooctadecane(18-crown-6) is described. Metal ions were accumulated at the electrode by complexing with the ionophore, reduction and detected by differential pulse anodic stripping voltammetry. A five-fold increase in the voltammetric response was achieved at the modified electrode compared to a bare glassy electrode. Parameters and conditions such as the modifier composition, the pH of supporting electrolyte, deposition potential, deposition time, and stripping mode were optimized. For five minutes preconcentration at DDTC in 100 mM KNO3, pH 2.5, linear calibration plots in the range 0.5 mu M to 50 mu M were obtained with a detection limit of 10 nM. For 18-crown-6, after accumulation at open circuit for 1 minute, a linear plot between 2 and 40 mu M was achieved. The lifetimes of each electrode were more than three weeks.