Mass-independent isotopic fractionation of tin in chemical exchange reaction using a crown ether.

Tin isotopes were fractionated by the liquid-liquid extraction technique with a crown ether, dicyclohexano-18-crown-6. The isotopic ratios of (m)Sn/(120)Sn (m: 116, 117, 118, 119, 122 and 124) were measured by multi-collector inductively coupled plasma spectrometry (MC-ICP-MS) on a Nu Plasma 500 with a precision better than 0.05 permil amicro(-1) on each isotopic ratio. Odd atomic mass isotopes ((117)Sn and (119)Sn) showed depletions compared to the even atomic mass isotopes ((116)Sn, (118)Sn, (122)Sn and (124)Sn). We show that this odd-even staggering property originates from the nuclear field shift effect. The contribution of the nuclear field shift effect to the observed isotope enrichment factor was estimated to be approximately 35%.