Separation of thorium, uranium and rare-earth elements with 2-[(2-arsenophenyl)-azo]-1,8-dihydroxy-7-[(2,4,6-tribromophenyl)azo]-naphthalene-3,6-disulfonic acid by capillary electrophoresis

The separation of thorium, uranium and rare-earth elements (RE) as their 2-[(2-arsenophenyl)-azo]-1,8-dihydroxy-7-[(2,4,6-tribromophenyl)azo]-naphthalene-3,6-disulfonic acid complexes by capillary electrophoresis with direct UV–Vis detection is presented in this paper. The influences of pH value and concentration of electrolyte, voltage and surfactant on separation were investigated and optimized. Under the selected conditions (30 mM NaAc–HCl buffer containing 0.5 mM cetyltrimethylammonium bromide and 0.2 mM chelating reagent, pH 4.30, 12 KV, 635 nm as detection wavelength), the coexisted ions were separated within 4 min, and limits of detection of 37, 39, 199 μg l−1 for RE, thorium, uranium with a linear dynamic range of over 2 orders of magnitude were achieved, respectively.