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

An epoxy-carbon powder composite electrode bulk modified with 8-hydroxyquin oline was fabricated for the continuous flow and flow injection anodic diff erential pulse voltammetric determinations of Sn(II) after open circuit pre concentration. Factors affecting Sn(II) determination were systematically i nvestigated and an optimized procedure was developed. Under the optimized c onditions for the continuous flow system with 10 min accumulation, the cali bration plot was linear from 5.00 x 10(-9) to 1.00 x 10(-6) M and a detecti on limit of 4.6 x 10(-10) M (0.055 ppb, S/N = 3) was found. For six consecu tive differential pulse stripping experiments each of Sn(II) concentrations of 5.00 x 10(-9), 5.00 x 10(-8) and 5.00 x 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 mu l injection of 0.91 x 10(-8) M, S/N = 3) was achieved. Selected metal ions and other substances were investigated for interferences. The developed met hod was tested with a spiked United States Environmental Protection Agency water quality control sample (USEPA WP 386) and then applied to the determi nations of tin in human hair, canned fruit juice and spiked sea-water sampl es.