ストリッピング分析法による鉄鋼中微量銅,鉛,カドミウムおよび亜鉛の同時定量

抄録

A simple and reliable method is described for the simultaneous determination of copper, lead, cadmium and zinc at the μgg^-1 level in iron and steel by two different stripping techniques without any preliminary separation of the iron matrix. Constant current stripping analysis (CCSA) at a mercury-coated glassy carbon electrode was compared with anodic stripping voltammetry (ASV) at a hanging mercury drop electrode. Analyte ions in nitric-sulfuric acid mixture solutions (pH=4 for ASV) were electrodeposited on the working electrode with stirring at a controlled potential for 3 to 10 min. The deposits were then anodically stripped at a constant current of +30μA for CCSA or in the potential range -1.2 to -0.2V vs. SCE at a scan rate of 20mVs^-1 by a differential pulse mode for ASV. The interference of iron(III) was eliminated by reducing it with L(+)-ascorbic acid to iron(II). The influence of foreign elements on the determination was evaluated. The lower limits of determination for CCSA and ASV were 50 and 0.5μgg^-1 of lead, cadmium and zinc in iron and steel, respectively. Differential pulse ASV had high sensitivity and poor peak resolution compared with CCSA. The simultaneous determination of 5 to 60ugg^-1 of these four elements in iron was achieved with the relative standard deviations (n=5) of less than 7% within 12 min. Recoveries for the analytes ranged from 88 to 108%. The proposed methods can be also applied to the simultaneous determination of tramp elements in obsolete steel scrap.