Adsorption voltammetry of the scandium-alizarin red S complex onto a carbon paste electrode

For the first time, a new method is described for the determination of scandium based on the cathodic adsorptive stripping of the scandium-alizarin red S complex onto a carbon paste electrode. The second-order derivative linear scan voltammograms of the complex are recorded by use of model JP-303 polarographic analyzer from 0.0 to −1.0 V (versus SCE). Optimum conditions are found to be: an acetic acid (0.36 mol l−1)-potassium biphthalate (0.064 mol l−1) buffer solution (pH 4.0) containing 2.0×10−5 mol l−1 alizarin red S, a preconcentration potential of 0.0 V, a preconcentration time of 60 s, a rest time of 10 s and a scan rate of 100 mV s−1. The results show that the complex can be adsorbed on the surface of a carbon paste electrode, yielding one peak at −0.58 V, corresponding to the reduction of alizarin red S in the complex at the electrode. The detection limit is found to be 6.0×10−10 mol l−1 for 3 min of preconcentration time. The linear range is 1.0×10−9 to 4.0×10−7 mol l−1. Application of the procedure to the determination of scandium in the ore samples gave good results.