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 (D DTC) or 1,4,7,10,13,16-hexaoxacyclooctadecane(18-crown-6) is described. Met al 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 modi fied electrode compared to a bare glassy electrode. Parameters and conditio ns such as the modifier composition, the pH of supporting electrolyte, depo sition potential, deposition time, and stripping mode were optimized. For f ive minutes preconcentration at DDTC in 100 mM KNO3, pH 2.5, linear calibra tion 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 mi nute, a linear plot between 2 and 40 mu M was achieved. The lifetimes of ea ch electrode were more than three weeks.