Nuclear field shift effect of chromium(III) in repeated extraction using a crown ether

Fujii, Toshiyuki*; Suzuki, Daisuke   ; Yamana, Hajimu*

Chromium isotopes were fractionated by continuous extraction using dicyclohexano-18-crown-6 as an extractant. This system was designed for accumulating isotope effect into the aqueous phase. After a long period operation, the Cr isotope ratios in the residual aqueous phase were precisely measured by using a multi-collector thermal ionization mass spectrometer with the total evaporation technique. The analytical results showed a clear mass-independent isotope fractionation. The mass-independent property was consistent with that obtained from a batch extraction. The isotopic mass balance was verified to be preserved in the continuous extraction. The Bigeleisen's 1996 theory gave the consistent explanation on the Cr isotope effect, in which the mass-independent isotope effect was identified to be the nuclear field shift effect.