An osmotic effect operative in frontal gel chromatography

The osmotic effect operative in frontal gel chromatography was quantitatively studied. When mixtures of a non-penetrating solute (Kav = 0) and a partially penetrating solute (0 less than Kav less than 1) were subjected to frontal gel chromatography, the latter formed a coextensive concentration gradient across the trailing boundary of the former, leading to the formation of a second plateau where the concentration exceeded that of the original solution plateau. It was shown that this anomaly, which we have previously predicted, was a direct consequence of osmotic perturbation of the bead size of the Sephadex gel and could be satisfactorily described by an equation based solely on the osmotic distention of the gel beads. Finally, the implications of the osmotic effect in the frontal chromatographic analysis of acceptor-ligand interactions is discussed and a method for correcting this effect is presented.