Voltammetric and EQCM Studies on Selenium(IV) at Mercury, Gold and Glassy Carbon Electrodes in the Presence of Cu(II), Au(III), Pb(II) and Cd(II)

Abstract

Cyclic voltammetry (CV), adsorptive stripping voltammetry (AdSV) and electrochemical quartz crystal microbalance (EQCM) were employed to study the behavior of selenium(IV) at the mercury, gold and glassy carbon electrodes. Optimum measurement parameters and stock solution compositions were established. Selenium(IV) was studied in the presence of copper, gold, lead and cadmium ions. At the glassy carbon electrode, selenium and gold were found to be too slightly electroactive to be determinable. However, in view of the copious release of Se-Au in the EQCM experiment involving the gold electrode, a voltammetric procedure was developed to determine the two elements. Peak current intensities recorded in relation to a Se(IV)/Au(III) mixture concentration yielded a linear relationship over the concentration ranges 3–9 μg mL−1 Se in the presence of 10 μg mL−1 Au, over 3–6 μg mL−1 Au in the presence of 10 μg mL−1 Se, and over 4–10 μg mL−1 Se(IV) in the presence of 16 μg mL−1 Cu(II). Statistical analysis of the results obtained showed the procedures to be useful for determining Se(IV) and Au(III) at the glassy carbon electrode with a satisfactory accuracy and precision. In AdSV method a control growth mercury drop electrode (CGMDE) was used as the working electrode and 0.1 mol L−1 HClO4 solution containg Cu(II) as supporting electrolyte. This method was applied to selective Se(IV) determination in pharmaceutical preparations (tablets) after microwave digestion. The results obtained by AdSV were compared with those obtained by AAS method. Nickel nitrate was used as a modifier in AAS method. The procedure developed enables selenium to be determined quantitatively with a satisfactory accuracy and precision in multicomponent tablets with no need for isolating it from the matrix.