Separation of Lithium Isotopes by Tetraazamacrocycles Tethered to Merrifield Peptide Resin

Tetraazamacrocyclic ion exchangers tethered to Merrifield peptide resin (DTDM, TTTM) were prepared and the ion exchange capacity of these was characterized. The isotope separation of lithium was determined using breakthrough method of column chromatography. The isotope separation coefficient was strongly dependent on the ligand structure by Glueckauf's theory. We found that the isotope separation coefficients were increased as the values of distribution coefficients were increased. In this experiment the lighter isotope, ⁶Li was enriched in the resin phase, while the heavier isotope, ⁷Li in the solution phase. The ion radius of lighter isotope, ⁶Li was shorter than the heavier isotope, ⁷Li. The hydration number of lithium ion with the same charge became small as mass number was decreased. Because ⁶Li was more strongly retained in the resin than ⁷Li, the isotopes of lithium were separated with subsequent enrichment in the resin phase