Determination of trace tin in flow systems at an epoxy–carbon powder–8-hydroxyquinoline composite electrode

Abstract

An epoxy–carbon powder composite electrode bulk modified with 8-hydroxyquinoline was fabricated for the continuous flow and flow injection anodic differential pulse voltammetric determinations of Sn(II) after open circuit preconcentration. Factors affecting Sn(II) determination were systematically investigated and an optimized procedure was developed. Under the optimized conditions for the continuous flow system with 10 min accumulation, the calibration plot was linear from 5.00 × 10⁻⁹ to 1.00 × 10⁻⁶ M and a detection limit of 4.6 × 10⁻¹⁰ M (0.055 ppb, S/N = 3) was found. For six consecutive differential pulse stripping experiments each of Sn(II) concentrations of 5.00 × 10⁻⁹, 5.00 × 10⁻⁸ and 5.00 × 10⁻⁷ M (10 min accumulations), relative standard deviations of 9.68, 7.45 and 3.38%, respectively, were obtained. For the flow injection mode, a detection limit of 5.4 ng (500 μl injection of 0.91 × 10⁻⁸ M, S/N = 3) was achieved. Selected metal ions and other substances were investigated for interferences. The developed method was tested with a spiked United States Environmental Protection Agency water quality control sample (USEPA WP 386) and then applied to the determinations of tin in human hair, canned fruit juice and spiked sea-water samples.