ADSORPTION VOLTAMMETRY OF THE COPPER-4-[(4-DIETHYLAMINO-2-HYDROXYPHENYL)AZO]-5-HYDROXYNAPHTHALENE-2,7-DISULFONIC ACID (BERYLLON III) SYSTEM

A sensitive adsorptive voltammetric procedure for the determination of trace copper, based on the adsorption characteristics of the copper(II) complex with Beryllon III at a hanging mercury drop electrode (HMDE), is described. The results show that the best base solution consists of 0.02 mol l-1 acetic acid, 0.005 mol l-1 sodium acetate and 1 X 10(-6) mol l-1 Beryllon III. The limit of detection and the linear range of the derivative linear sweep adsorption voltammetric method are 5 X 10(-10) and 1 X 10(-9)-2 X 10(-7) mol l-1, respectively. The method was applied to samples of digested human hair and to distilled water. The electrochemical behaviour of the copper complex with Beryllon III at the HMDE was also investigated in this medium. Adsorption phenomena were observed. The mechanism of the electrode reaction was found to be reduction of the copper complex adsorbed on the surface of the electrode by a totally irreversible charge transfer to metal amalgam.