Determination of tin in iron and steel by differential pulse anodic stripping voltammetry at a rotating gold film electrode

A simple and sensitive method is described for the determination of tin in iron and steel by differential pulse anodic stripping voltammetry at a gold-coated glassy carbon electrode. Tin(IV) could be quantitatively eletctrodeposited by the addition of high concentrations of bromide. The interference of the iron(III) matrix was eliminated by reducing it to ironn (II) with L(+)-ascorbic acid. Pre-electrolysis was carried out in 0.3 mol dm(-3) hydrochloric acid-0.1 mol dm(-3) nitric acid containing 2 mol dm(-3) sodium bromide and 0.2 mol dm(-3) L(+)-ascorbic acid at a potential of -0.5V as. Ag/AgCl for 300 s. The deposits were stripped at a scan rate of 40 mV s(-1) to 0 V vs. Ag/AgCl. The calibration (peak height as. tin (IV) concentration) graph in the presence of 1000 mug cm(-3) Fe(II) was linear over a concentration range 8.3. x 10(-9) to 3.4 x 10(-7) mol dm(-3) of tin(IV) and passed through the origin, with a relative standard deviation of 4.3% for 20 ng cm(-3)(n = 5). The detection limit (3 sigma) was 2.8 x 10(-9) mol dm(-3). There were serious interferences due to overlapping stripping peaks of cadmium (II) and copper( II). The determination of 120 to 400 mug g(-1) of tin in iron and steel was achieved with good precision and accuracy within 50 min without any preliminary separation of the matrix. The proposed method is applicable to the determination of tin down to 1 mug g(-1) levels in scrap iron.