Further Results on Behaviors of Rare Earth Metal Ions in Centrifugal Partition Chromatography with DI(2-Ethylhexyl) Phosphoric Acid

Abstract

In centrifugal partition chromatography (CPC) of rare earth metal ions (RECl₃) by the use of di(2-ethyl-hexyl)phosphate (D2EHPA) as “separator” in the stationary phase, effects of number of microcells and stationary solvent were investigated for improving separation. By increasing the number of microcells from 1200 (3 cartridges) to 2400 (6 cartridges), the peak resolution value (R) for the separation of PrCl₃ versus NdCl₃ was improved from 0.37 to 0.62. Heavier RE ions (ErCl₃ and YbCl₃) was able to separate almost completely by using CHCl₃ as stationary solvent. This result suggests that by adjusting these two factors, in addition to adjusting [HC1] in the mobile phase (previously reported), almost whole series of adjacent couples of RE ions will be effectively separated by CPC with acidic D2EHPA. In contrast, neutral tri-n-butyl phosphate (TBP) was found to be a poor separator.