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 ε84-88=0.0075 to ε84-88=0.0263. The maximum, ε84-88=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.