Fig. 6 shows the structure of the three ligands compared in this study according to wikipedia site. The malate structure has up to 4 possible active sites for complexion with Nd ions. This number is reduced to three only in case of citrate, as two sites were not available for complexion due to steric hindering. Glycolate has only one possible site for complexion with Nd. The number of possible complexion sits of the three ligands takes the order Malate > Citrate > Glycolate, which agree with the order of isotope effects of the three systems as studied by the separation coefficients shown above.