2005 Volume 91 Issue 7 Pages 595-601
A sensitive anodic stripping voltammetric method for the simultaneous determination of zinc, lead and bismuth in steel is described. The interference of the iron(III) matrix was eliminated by reducing it to iron(II) with L(+)-ascorbic acid. The optimized experimental conditions were as follows: analyte ions in a steel sample solution containing a nitric-sulfuric acid mixture (pH=2) were electrodeposited as metals on a hanging mercury drop electrode at-1.2 V vs. Ag/AgCl for 5 min with stirring; the deposits were then anodically stripped in the potential range -1.2 to 0 V vs. Ag/AgCl at a scan rate of 50 mV s-1 by a differential pulse mode. Linear relationships held between the peak height and the concentrations of analyte ions in the concentration range 5 to 200 ng mL-1 with relative standard deviations below 5% for 30 ng mL-1. The detection limits (3σ) were less than 1.7 ng mL-1 for the deposition time of 5 min. The influence of foreign elements on the determination was evaluated, and a method for eliminating the interference from other metal ions, in particular copper and nickel, due to the formation of intermetallic compounds with zinc in amalgams was devised. The proposed method was applied to the simultaneous determination of 3.5 to 325 μgg-1 of zinc, lead and bismuth in steels with good precision and accuracy.
