Development of Mercury Film Electrode for Cadmium Ion Determination using Voltammetry

Abstract

The technique of stripping voltammetry is commonly used to determine the trace level of metal ions. A working electrode is usually used the mercury film electrode affixed to the surface of glassy carbon (GC) electrodes. GC electrodes are difficult to create and have relatively expensive prices. This study developed a mercury film electrode on the pencil surface for cadmium ion analysis in anodic stripping voltammetry. The process was conducted in two phases. First, deposition of Hg in solution Hg(NO₃)₂ 10 mM with deposition potential 1,000 mV vs Ag/AgCl (NaCl 3M) and deposition time 90 seconds. This deposition produced mercury film covering the entire surface of the disc electrode evenly. Second, on the measurement stage, Cd²⁺ ion was deposed on a potential -1,100 mV vs Ag/AgCl (NaCl 3M) with deposition time 90 seconds and then Cd in amalgam dissolved by changing the working electrode potential to be more positive while keeping Hg sticking to the surface of the electrode. The limit detection measurement of cadmium ion is 0.085 ppm with the percentage of gain is 95.5% - 98.3%.