Square wave Stripping voltammetry of Cobalt Based on Adsorptive accumulation of its Hydroxynaphthol Blue (HNB) Complex at the Static Mercury Drop Electrode

Abstract

ABSTRACT A new method is described for the determination of cobalt based on the square wave adsorptive stripping voltammetry of Co(II) complexed with hydroxynaphthol blue (HNB) at the static mercury drop electrode. Optimal conditions were found to be: preconcentration potential, -0.500V vs. Ag/AgCl (KCl 3M); preconcentration time, 30 s (with stirring); pulse height, 50 mV; frequency, 100 Hz; scan increment, 4 mV; step time, 0.010 s; supporting electrolyte, HEPES/HCl (0.1 M, pH 7.0-8.0) or triethanolamine/HCl (0.1 M, pH 7.6); concentration of hydroxynaphthol blue, 5.0 × 10−6 M. The response of the system was found to be linear in a range of Co(II) concentrations from 2.0 to 10.0 μg/L. The limit of detection was found to be 1.8 × 10−9 M with 2 minutes of preconcentration time. The effect of various potential interferences were also studied including a variety of cations, anions and organic surfactants. The interferences by Ni(II), and Cr(VI) may be eliminated by addition of EDTA or CDTA and the of Fe(III) and Ti(IV) by fluoride. The merits of the procedure were demonstrated in the analysis of certified and biological samples.