Determination of Trace Tellurium in Steel and Lead by Cathodic Stripping Voltammetry Based on Non-Electrolytic Preconcentration

Abstract

Cathodic stripping voltammetry at a silver disk electrode based on non-electrolytic preconcentration steps is developed for the determination of trace amounts of tellurium in steel and lead. Tellurium(IV) ions were accumulated on a rotating silver disk electrode surface as silver telluride in 4 mL of acidic solutions (pH 0.7∼0.9) containing sodium bromide and L(+)-ascorbic acid for 30 min with open circuit. A differential pulse cathodic stripping voltammogram for the deposits was then recorded in another cell with a 2 mol·L⁻¹ sodium hydroxide solution in the potential range −0.45 to −1.5 V vs. Ag/AgCl at a scan rate of 50 mV· s⁻¹. The presence of bromide ions allowed the non-electrolytic preconcentration of silver telluride and resulted in a single distinct peak. Maximum permissible concentrations of iron(II) and lead(II) in the determination of 100 μg·L⁻¹ of tellurium(IV) were 1000 and 4000 mg·L⁻¹, respectively. Iron(III) was reduced to iron(II) with L(+)-ascorbic acid. Calibration curve was linear over the 7.8×10⁻⁸ to 2.4×10⁻⁶ mol·L⁻¹ concentration range and passed through the origin. The detection limit (3σ) calculated from repeated determinations of 3 μg·L⁻¹ of tellurium(IV) was 0.31 μgTe·L⁻¹. The advantages of the proposed method include simple and rapid operations and lessening contamination hazards. The method was successfully applied to the determination of tellurium at the 10 mass ppm level in 1-g samples of alloy steel and battery lead without any troublesome separation of the matrix element using harmful chemicals. The relative standard deviations were 3 to 5% for five determinations, and the time required for an analysis was less than 1 h.