Rapid, high-purity, lanthanide separations using HPLC

High-purity chromatographic methods for separating five pairs of neighboring lanthanide elements (Tm/Er, Gd/Eu, Eu/Sm, Sm/Pm, and Pm/Nd) have been developed for the purpose of producing radioactive targets for neutron capture experiments. The methods employ high-performance liquid chromatography (HPLC) with CS-3 Dionex cation exchange columns that were optimized for each set of elements to obtain the greatest peak separation as a function of the concentration and pH of the alpha-hydroxyisobuturic acid (alpha-HIB) eluent. Our results indicate a minimum separation resolution (SR) of 2.8 was obtained between each pair of neighboring lanthanides and an overall average SR of around 4.0 within 15 min time. These results represent a significant enhancement over previous chromatographic methods using other technologies (i.e., reverse-phase resins) as well as those based upon similar instrumentation. We attribute our success here to two factors: (1) optimizing the eluent to effect the greatest separation between individual pairs of lanthanides, and (2) altering pH as well as concentration of the eluent for each specified lanthanide pair. Implications of these results to rapid, high-purity lanthanide group separations for general analytical purposes as well as for specialized applications in the area of nuclear attribution (NA) are discussed. (c) 2005 Elsevier B.V. All rights reserved.