Subnanomolar Determination of Indium by Adsorptive Stripping Differential Pulse Voltammetry Using Factorial Design for Optimization

A highly sensitive method to determine of indium is proposed by adsorption stripping differential pulse cathodic voltammetry (AdSDPCV) method. The complex of indium ions with xylenol orange is analyzed based on the adsorption collection onto a hanging mercury drop electrode (HMDE). After accumulation of the complex at −0.20 V vs. Ag/AgCl reference electrode, the potential is scanned in a negative direction from −0.40 to −0.75 V with the differential pulse method. Then, the reduction peak current of In(III)–XO complex is measured. The influence of chemical and instrumental variables was studied by factorial design analysis. Under optimum conditions and accumulation time of 60 s, linear dynamic range was 0.1–10 ng/ml (8.7 × 10−10 to 8.7 × 10−8 M) with a limit of detection of 0.03 ng/ml (2.6 × 10−10 M); at accumulation time of 5 min, linear dynamic range was 0.04–10 ng/ml (3.4 × 10−10 to 8.7 × 10−8 M) with a limit of detection of 0.013 ng/ml (1.1 × 10−10 M). The applicability of the method to analysis of real samples was assessed by the determination of indium in water, alloy, and jarosite (zinc ore) samples.