[en] The isotope fractionation of calcium has been obseved in cation exchange chromatographic Processes. It is found that the heavier isotope is preferentially retained by the resin phase in the case of a strongly acidic cation exchange resin, while the lighter isotope is enriched in the resin phase with a weakly acidic cation exchange resin. Estimated values of the elemental separation coefficient epsilon (per unit mass) are 0.3 x 10^-4 in Ca-acetate, 0.5 x 10^-5 in Ca-citrate for the strongly acidic cation exchange resin, and 0.3 x 10^-4 for the weakly acidic cation exchange resin. (author)