IMPROVED SEPARATION AND DETERMINATION OF RARE-EARTH-METAL IONS IN REAL SAMPLES BY CAPILLARY-ELECTROPHORESIS WITH INDIRECT UV DETECTION

The separation of rare earth metal ions by capillary electrophoresis i n the presence of imidazole as the UV-absorbing background electrolyte , and lactic acid or alpha-hydroxyisobutyric acid (alpha-HIBA) as the complexing agent, with indirect UV absorbance detection was investigat ed. The effects of various acids in the running buffer, pH of buffer a nd the concentration of complexing agent on the separation were examin ed. It was observed that the acid used for adjusting the pH of the buf fer was another important factor, besides the concentration of the com plexing agent that affects the separation of rare earth metal ions. Th e results showed that under a positive voltage of 10.0 kV, fourteen ra re earth metal ions could be baseline separated within 9 minutes using 0.02 mol/l imidazole containing 8x10(-3) mol/l alpha-HIBA at pH 3.4 a djusted with hydrochloric acid. The detection limits of La. Ce, Pr. Nd , Sm and Tb were 5x10(-6) mol/l. The contents of La, Ce, Pr, Nd and Sm in real samples from Gansu Rare Earth Company were determined quantit atively using Tb (III) as an internal standard. The results were consi stent with those of ICP.