Use of Di-(2-ethylhexyl) Orthophosphoric Acid for the Separation of the Rare Earths by Reverse Phase Partition Chromatography

Abstract

IT has been shown that relatively large separation factors may be obtained for adjacent rare earths by liquid-liquid extraction if di-(2-ethylhexyl) orthophosphoric acid (HDEHP) is used as the organic extractant1. In an earlier communication2 we have considered the possibility of exploiting the properties of HDEHP for separating the elements from lanthanum to gadolinium by reverse phase partition chromatography, the HDEHP being retained on a solid support, packed to form a chromatographic column. It was found that the elements were removed from dilute perchloric acid to form a band at the top of the column, and then could be eluted successively in the order of increasing atomic number by means of perchloric acid of gradually increasing strength, good resolution of the individual rare earths being obtained. Further investigations have now shown that this technique may be extended to provide a separation of the heavy rare earths terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, gradient elution again being used to provide column influents of the wide range of acidities necessary for the elution of these elements.