SIMULTANEOUS DETERMINATION OF COPPER, SIL VER AND CADMIUM IN HIGH-PURITY ZINC BY ICP-AES AFTER EXTRACTION AND BACK-EXTRACTION

The separation and simultaneous determination of trace amounts of Cu, Ag, and Cd in high-purity Zn were studied. After the sample was dissol ved in a mixture of sulfuric acid and nitric acid, Cu, Pig and Cd were separated from Zn by extraction into xylene as diethyldithiocarbamate s complexes using diethylammonium diethyldithiocarbamate (DDDC), and t hen back-extracted into nitric acid for a determination by ICP-AES. Th e recoveries of Cu, Ag and Cd were satisfactory throughout the extract ion with 2.5x10(-2) mol/l DDDC in xylene from 0.25 mol/l sulfuric acid -0.1 mol/l nitric acid solution and the back-extraction with 7.5 mol/l nitric acid. The extractions of Cu, Ag and Cd were suppresed in the p resence of hydrochloric acid. The diverse elements in Zn caused no int erference for the determination of Cu, Ag and Cd. The recoveries of Cu , Ag and Cd decreased somewhat with increasing the added amount of Zn. Thus, the standard addition method should be applied for the determin ation of these metals. The detection limits were found to be 0.17 mu g /g for Cu, 0.12 mu g/g for Ag and 0.07 mu g/g for Cd using 1 g of a Zn sample. The proposed method was applied to an analysis of the referen ce material, the results agreed with the certified values.