Separation of Ce from other rare-earth elements with application to SmNd and LaCe chronometry

The rare-earth element (REE) pairs SmNd and LaCe include three radioactive decay systems that are used in geo- and cosmochemistry for dating and tracer studies. Efficient chemical separation techniques are required prior to isotopic analysis of Ce and Nd. Matrix elements with low work functions must be removed from samples, since they can have a severe effect on ionization efficiency; isobars from other elements must also be eliminated in order to reduce interference corrections. These steps are particularly important for high-precision measurements, such as for 142Nd/144Nd or Ce isotope analyses. e report a simple but highly efficient two-phase micro-extraction technique for the separation of Ce from the other REE. The procedure involves oxidation of Ce3+ to Ce4+ using a solution of NaBrO3 in nitric acid and extraction of the tetravalent species into an organic solvent containing HDEHP. The other lanthanides remain trivalent and are thus left in the aqueous nitric acid phase. The method is characterized by high elemental yields, excellent separation factors and low reagent blank contributions. lvent extraction method has been successfully used for (1) cleaning of Nd from Ce contamination and (2) the isolation of Ce from other REE for mass spectrometry. Isotopic analyses of the extracted samples showed minimal isobaric interferences, demonstrating that the technique achieves separation factors superior to standard procedures.