REVERSED-PHASE SEPARATION OF TRANSITION-METALS, LANTHANIDES AND ACTINIDES BY ELUTION WITH MANDELIC-ACID

Mandelic acid was investigated as an eluent for the determination of inorganic cations via dynamic ion-exchange and 'hydrophobic interaction' chromatography. Mandelic acid displays similar complexation chemistry to alpha-hydroxyisobutyric acid, but it is a more hydrophobic ligand and thus the resultant metal-ligand complexes are retained more strongly by the reversed phase surface. The retention behaviour of transition metals, lanthanides and actinides was studied. Retention of the actinides depends on the concentration and pH of the mandelic acid eluent. the column temperature and the concentration of organic modifier. Increasing either the column temperature or the eluent pH above 3.5 altered the selectivity between the actinides. Near-baseline separation was achieved for U, Am, Pu, Np and Th with mandelic acid eluent using isocratic conditions.