Separation and determination of thorium, uranium and mixed rare-earth elements as their UV/Vis absorbing complexes by capillary zone electrophoresis

Separation and determination of thorium, uranium and mixed rare-earth elements (RE) as their 2-(2-arsenophenylazo)-1, 8-dihydroxyl-7-(4-chloro-2, 6-dibromophenylazo) -naphthalene-3,6-disulfonic acid (DB C-As) complexes by capillary electrophoresis is presented in this paper. The pre-column derivitization conditions are discussed. Some separation parameters such as pH value, type of carrier electrolyte, applied voltage, the concentration of ligand in buffer and the sample size are also optimized. Under the selected conditions, the complete separation of thorium and uranium from mixed RE was accomplished in 10 min. Quantitative analyses exhibited an excellent linear dynamic relationship in the range of over two orders of magnitude. Detection limits of 4.81 x 10(-8), 7.23 x 10(-8), and 59.4 x 10(-8) mol l(-1) for RE, Th and U were obtained, respectively. This method was applied to the determination of these metal ions in ore samples. (C) 1998 Elsevier Science B.V. All rights reserved.