Preparation of copper amalgam (CuHg) as working electrode for analysis of selenium

Abstract

Selenium is an essential trace element for human. Beside the range of concentration, the beneficial and toxic effects of selenium are also depending on which chemical form it takes. In nature or environment and some organisms, selenium is present both in organic and inorganic forms where some studies revealed that inorganic species especially selenite are more toxic than the organics matter. Various methods are used to analyse selenium, but it is usually to determine the total selenium, not designed for field applications, requires several preparation steps prior to actual determination, and needs a lot of chemicals. These problems can be solved by voltammetry methods by using dropping or film mercury as a working electrode. The nature of poisonous mercury becomes a limitation in the use of this working electrode. A copper amalgam (CuHg) as working electrodes was successfully prepared for the analysis of selenium. CuHg working electrode was made in a simple way, namely by deposition of copper (Cu) on the surface of Cu wire with potential and at certain time, then dipped into a solution of saturated mercury salt to form the amalgam. Cyclic voltammetry was used to investigate the electrochemical properties of selenium with 0.1 M HCl as a supporting electrolyte. Cyclic voltammetry technique was conducted on the working potential range of - 300 mV (Ei) to -800 mV (Ef). Profiles of cyclic voltammogram were influenced by the scan rate applied. In addition, SEM images showed that the adsorption of selenium occurred on the surface of CuHg working electrode.