Rare earth elements are important for many scientific applications. The purity and separation of lanthanides is very important for these technologies. Cation exchangers and elution by complexing agents are commonly used for the separation of lanthanides by the use of ion exchange methods. Within the group of hydroxyacids, α-hydroxyisobutyric acid (α-HIBA), is used as an eluent and is one of the most favourable eluents in this group. α-HIBA, buffered with ammonium hydroxide (NH4OH), results in good separation of dysprosium(III) (Dy), terbium(III) (Tb) and gadolinium(III) (Gd) and can be used at room temperature. Simply increasing the concentration of α-HIBA gives elution of the lanthanides, but little is know about the effect of the pH of the eluent.