Strontium isotope effects in ligand exchange reaction

Strontium isotope effects in ligand exchange reaction were investigated. Strontium chloride was extracted into dicyclohexano-18-crown-6/chloroform from the aqueous phase of 4-9 M HCl/H2O. The distribution ratios of strontium increased with HCl concentrations. Strontium extracted into the organic phase had a complex form of Sr2+ crown, Sr2+- crown-HCl or Sr2+-crown-(HCl)(2) depending on the concentration of hydrochloric acid in the aqueous phase. Isotope enrichment factors changed from epsilon(84-88)=0.0075 to epsilon(84-88)=0.0263. The maximum, epsilon(84-88)=0.0263 was found at the complex form of Sr-crown-(HCl)(0.5) in the organic phase, where Sr-crown and Sr-crown-HCl coexisted at a ratio of 1 : 1. The enrichment factor dependency on HCl concentrations was found to be brought about from complex forms in the organic phase; Sr-crown in the diluted HCl system, Sr-crown-HCl in the medium HCl system, and Sr-crown-(HCl)(2) in the concentrated HCl system.