Comparative study of stationary phases impregnated with acidic organophosphorus extractants for HPLC separation of rare earth elements

ABSTRACTChromatographic separation behavior of rare earth elements (REEs) on reversed-phase columns impregnated with di-(2-ethylhexyl) phosphoric acid (H[DEHP]), 2-ethylhexyl, 2-ethylhexyl phosphonic acid (H[(EH)EHP]) and di-(2,4,4-trimethylpentyl) phosphinic acid (H[TMPeP]) were compared utilizing nitric acid as eluent and ICP-MS for detection. Retention factors were determined and compared under the same eluting conditions using columns loaded with approximately 0.4 mmole of each extractant. The separation efficiency was evaluated from resolution data of the REEs acquired under same and optimized elution conditions for each column. The best separation for the entire series of REEs was obtained with H[(EH)EHP], H[DEHP] was found more appropriate for lighter REEs and H[TMPeP] was the best choice for separation of heavy REEs.