Determination of molybdenum by adsorptive catalytic stripping voltammetry in the presence of alizarin red s and persulphate

Abstract

An alternative and sensitive method by adsorptive catalytic stripping voltammetry for the determination of trace molybdenum is proposed. The method is based on the adsorption collection of the Mo(VI)-Alizarin Red S complex on a hanging mercury drop electrode (HMDE) following the catalytic reduction of both Mo(VI) and Alizarin Red S (ARS) in the complex in the presence of persulphate as oxidizing reagent. The experimental parameters such as accumulation time, accumulation potential, scan rate, pH, concentration of ARS and persulphate were optimized. Under the optimized conditions, the relationship between the peak current and molybdenum concentration is linear in the range of 0.15-5.0 mu g/L. The detection limit and quantitation limit of the method based on the standard deviation of blank for accumulation time of 30 s were calculated as 0.046 mu g/L (4.79x10(-10) M) and 0.15 mu g/L (1.56x 10(-9) M), respectively. The method was applied to the determination of molybdenum in drinking water samples. The recoveries for 1 and 3 mu g/L molybdenum in the drinking water samples were found as 90% and 93%, respectively. Relative standard deviation for 3 mu g/L molybdenum is 2.88%. 100 mu g/L As(III), Ni(II) and Zn, 50 mu g/L Al(III) did not interfere while serious interference was observed from Sb(III). Voltammetric characteristics and mechanism of the Mo(VI)-ARS-S(2)O(8)(2-) system were also investigated.