CHROMATOGRAPHIC-SEPARATION OF CALCIUM ISOTOPES WITH POLYMER-BOUND LIGANDS

Calcium isotopes were enriched in chromatography columns containing the polymer-bound ligands cryptand [2B22], cryptand [2B21], and 18-Crown-6. The largest equilibrium single stage separation factor, 1.0039 +/- 0.0002 for the calcium 40/44 isotope pair, was found in calcium exchange with cryptand [2B22]. The largest separation factor found for 18-Crown-6 was 1.0025 +/- 0.0003 for the 40/44 isotope pair. The size of the isotope effect was found to be highly dependent on the solvent composition. An iminodiacetate resin ion exchange column yielded small enrichments of calcium isotopes. Calcium 40/44 exchange with the chelating functional group iminodiacetate yielded a small equilibrium separation factor of 1.00011 +/- 0.00003, which was more typical of calcium ion exchange isotope effects. Comparisons of the above chemical system based on separative power showed crown chemical exchange to be an improvement over cryptand and iminodiacetate exchange. The cryptand system was rendered impractical as a consequence of a slow exchange rate and a resulting large stage residence time contribution to the separative power, on the order of 45 min. The separation factor for the iminodiacetate system was too small for practical applicability.