Sensitive Determination of Bismuth in Iron and Steel by Stripping Voltammetry after Extraction of the Matrix

A highly sensitive method is described for the determination of bismuth by differential pulse anodic stripping voltammetry after preliminary separation of iron matrix. Most of the iron in an acidic sample solution was removed by the 4-methyl-2-pentanone (MIBK) extraction method, and MIBK dissolving in the aqueous phase was then removed by extracting three times with cyclohexane. Bismuth(III) remaining in the aqueous phase was electrodeposited on a rotating glassy carbon disk electrode at -0.6 V vs. Ag/AgCl for 600s with stirring; the deposit was then anodically stripped at a scan rate of 50 mVs(-1) to 0.2V vs. Ag/AgCl. The calibration (peak height vs. Bi(III) concentration) graph was linear over the concentration range of 5 to 75 ng mL(-1)(correlation coefficient > 0.999), with relative standard deviation of ca. 5% for 50 ng mL(-1) (n=3). The interference from copper(II) weakened somewhat by adding 1,2-diaminopropane-N,N,N,N'-tetraacetic acid. The minimum limit of determination of the proposed method was ca. 0.1 mu g g(-1), and bismuth at the mu g g(-1) level in iron and steel was determined with good precision and accuracy.