Trace analysis of lead and cadmium with gold and silver microelectrodes

In this study, microelectrodes made from gold (wire, 25 μm diameter, 4 cm length) and silver (band, 25 μm diameter, 7 mm length) were investigated for trace lead and cadmium analysis. The gold wires were electrochemically coated with mercury before use; the silver bands were used without coating. Preliminary studies of the behaviors of microelectrodes were examined. The microelectrodes exhibits specific characteristics such as high sensitivity, fast scan rate utility and possibility to be employed in unstirred condition. In the optimized conditions, repeatability of mercury plated gold (using LSV) were 4 % at Pb 70 ppb for 30 s deposition, 8 % at 30 ppb for 60 s deposition, 11 % at 10 ppb for 60 s deposition; and those of silver (using DPV) were 3 % at Pb 15 ppb for 30 s deposition, 2.3 % at ppb for 60 s. with silver electrodes and 60 s deposition time, the detection limits were 0.64 ppb for Pb, and 1.06 ppb for Cd. Finally, silver micro bands were successfully applied to the determination of Pb and Cd in tape water. (author)