The values of the separation coefficients were plotted as a function of the mass number at 25 °C as shown in Fig. 5. A linear relationship was obtained between the mass number and the separation coefficient for the three ligands. The current discussion cannot be extended to the odd–even or mass anomaly phenomena due to the short migration of the bands that leads to high errors in the isotope ratio measurements carried out by ICP mass. The odd–even and mass anomaly phenomena were discussed for neodymium malate system elsewhere [9]