SIMULTANEOUS DETERMINATION OF TRACE AMOUNTS OF BISMUTH AND ANTIMONY IN HIGH-PURITY TIN BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

The separation and determination of trace amounts of Bi and Sb in high-purity Sn were studied. After the sample was dissolved with mixture of phosphoric acid and sulfuric acid, Bi and Sb were separated from Sn by extracting into xylene with diethylammonium diethyldithiocarbamate (DDDC) and subsequently back-extracted into nitric acid for the determination by ICP-AES. Sn are little extracted from phosphoric acid solution, so it is possible to separate Bi and Sb from Sn. The apparent distribution ratios (D) of Bi, Sb and Sn between 5 x 10(-2) mol/l DDDC-xylene and 4 mol/l phosphoric acid-0.5 mol/l sulfuric acid were found to be 1.7 x 10(3) for Bi, 2.5 x 10(3) for Sb and 5.5 x 10(-3) for Sn. Therefore, the separation factors (S=D-m/D-sn.) of Bi and Sb from Sn are calculated to be 10(5) level, respectively. The recoveries of Bi and Sb were satisfactory throughout the extraction with 5 x 10(-2) mol/l DDDC in xylene from 4 mol/l phosphoric acid-0.5 mol/l sulfuric acid solution and the back-extraction with 60% nitric acid. Y was used as an internal standard for ICP-AES measurements. The diverse elements which are contained in Sn caused no interference for the determination of Bi and Sb. The detection limits were found to be 41 ng/g for Bi and 84 ng/g for Sb using Ig of Sn sample. The proposed method was applied to analysis of the real samples and a reference material with good results.