Theory of chromatography of rigid molecules on hydroxyapatite columns with small loads

Taves and Reedy postulated that phosphate ions are adsorbed at hydroxyl positions on the surface of hydroxyapatite, and proposed a model for the adsorption of tripolyphosphate on the crystal surface. On the basis of this model and the hypothesis that a hydroxyl position on the crystal corresponds to a chromatographic C site, the experimental chromatogram for a mixture of AMP, ADP, ATP and adenosine tetraphosphate obtained by Bernardi was analysed by using the theory developed in an earlier paper in this series. It was estimated that the energy of adsorption on a C site for a univalent phosphate group on the polyphosphate chain of nucloside polyphosphate is 0.9–1 kcal/mole and that the adenosine group of the molecule covers at most only one crystal site. Some other experimental parameters were lso evaluated. The reasonable results obtained in the calculation strongly support the hypothesis of the one-to-one correspondence between a hydroxyl position and a chromatographic C site and the model of Taves and Reedy.