Application of Liquid-Liquid Extraction if Lanthanoid Elements to Centrifugal Partition Chromatography

ABSTRACT Akiba, K., Ishibashi, Y. and Nakamura, S., 1990. Application of liquid-liquid extraction of lanthanoid elements to centrifugal partition chromatography. Extraction of lanthanoid elements (M) by 2-ethylhexyl 2-ethylhexylphosphonic acid (EHPA; HA) proceeds via the reaction, M 3+ aq + 3(HA) 2 , org ⇄ M(HA 2 ) 3 , org + 3H + aq . This liquid-liquid extraction has been modified to a centrifugal partition chromatography (CPC). An organic solution containing EHPA was held as a stationary phase and an aqueous mobile phase was passed through the stationary phase. The retention volume (V R ) is related to the distribution ratio (D) of the desired lanthanoid element, V R = V m + D·V S , where V S and V m are the volumes of the stationary and mobile phases, respectively. The addition of water-soluble alcohols enhanced the resolution of adjacent bands. The mutual separation of mixed lanthanoids, Sm-Eu-Gd, was accomplished by employing the ethylene glycol-water mixture as the mobile phase. The separation process in CPC essentially corresponds to that in liquid-liquid extraction.