The isotopes separation of certain element by ion exchange chromatography is best achieved by the band displacement technique. This operation is characterized by sandwiching a band of the ions of the element to be studied, Nd3+, between two other chemical species bands, Cu2+ and NH4+, maintaining self-sharpening band boundaries at both the migration band ends. During this operation, the band of the isotopic chemical species of the element to be separated is eluted through the column by a displacing eluent solution. The velocity of the band displacement is controlled by the eluent type and concentration in the solution phase, equilibrium between the solution phase and the resin phase as well as by the flow rate of the solution.