CYCLIC VOLTAMMETRY of H2SeO3 USING COPPER AMALGAM ELECTRODE LEADING TO ANALYSIS OF SELENIUM BY DIFFERENTIAL PULSE VOLTAMMETRY

• Main Author: Dara, Fitri
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/37686
• Institution: Institut Teknologi Bandung

Selenium is an essential trace element for human. Besides the range of concentration, the beneficial and toxic effects of selenium also depend on its chemical form. In natural environment and in the cell of some living organisms, selenium presents both in organic and inorganic forms. Based on some studies, the inorganic species are more toxic than organics ones, especially selenite. The concentration of selenium in natural water system is very low, with dominance of inorganic (selenite and selenate) species. Several analytical methods have been applied for routine analysis of selenium. However, there are some drawbacks that were encountered, such as: limited to the total selenium determination, huge or complicated instrument, time and chemicals consuming. In order to solve those problems, voltammetric methods that using dropping mercury or film mercury as a working electrode were explored. Nevertheless, due to the toxic property of mercury, it becomes a serious limitation in the use of this working electrode. In this work, a homemade copper amalgam (CuHg) and Ag/AgCl as working and reference electrodes respectively, has successfully been made for the analysis of selenium. CuHg working electrode was made by deposition of copper (Cu) on the surface of electrode with a particular potential and time, then dipped into a solution of saturated mercury salt to form the amalgam. Cyclic voltammetry and differential pulse stripping voltammetry with 0,1M HCl as a supporting electrolyte were employed to investigate the electrochemical properties and quantitative analysis of selenium. The experiments were conducted at the working potential range of -300mV (Ei) to -800mV (Ef). The results showed that the profiles of cyclic voltammogram were influenced by the concentration of selenium and applied scan rate. In addition, the number of cyclic repetition produces decreasing peak current intensity. These results show that selenium adsorption was occurred on the CuHg working electrode surface. Meanwhile, validation of this method were performed with an optimum parameters are as follows: -300mV (Ei) to -800mV (Ef), -450mV (Eacc), 300 seconds (tacc), 4mV/s (?), and 50mV for working potential range, accumulation potential , accumulation time, scan rate, and amplitude pulse, respectively. This method has a good precision with a relative standard deviation (%RSD) from 1,35% to 9,09% and accuracy with percent recovery as 108,9%. Linear calibration curve has a limit up to 397,14µM with a detection limit of 20µM.