Adsorption voltammetry of the mix-polynuclear complex of zirconium¯calcium¯alizarin red S at a carbon paste electrode

A novel new method is described for the determination of zirconium based on the cathodic adsorptive stripping of the mix-polynuclear complex of zirconium¯calcium¯alizarin red S (ARS) at a carbon paste electrode (CPE). The second-order derivative linear scan voltammograms of the adsorbed mix-polynuclear complex of zirconium¯calcium¯ARS are recorded by model JP-303 polarographic analyzer from +0.20 to 0.80 V (versus SCE). Optimal conditions are found to be: a glycine (0.096 M)¯potassium biphthalate (0.036 M) buffer solution (pH 4.0) containing 8.0×10-4 M Ca2+ and 2.0×10-5 M ARS; accumulation potential, +0.20 V; accumulation time, 90 s; rest time, 10 s; scan rate, 500 mV s-1. The results show that the complex can be adsorbed on the surface of the CPE, yielding one peak at -0.50 V, corresponding to reduction of ARS in the complex at the electrode. The detection limit is found to be 4.0×10-11 M with 4 min of accumulation time. The linear range is from 1.0 ×10-10 to 2.0×10-7 M. Application of the procedure to the determination of zirconium in the ore samples gives good results.