Although the ability to carry out simultaneous concentration and purification in a single displacement step has significant advantages for downstream processing of pharmaceuticals, a major impediment to the implementation of displacement chromatography has been the lack of suitable displacer compounds. An important recent advance in the state of the art of displacement chromatography has been the discovery that low-molecular-weight dendritic polymers can be successfully employed as displacers for protein purification in ion-exchange systems. In this article, protected amino acid esters (based on arginine and lysine) are shown to be useful displacers for protein purification in cation-exchange systems. A dynamic affinity plot is employed to evaluate the affinity of these low-molecular-weight compounds under displacement conditions. In contrast to large polyelectrolyte displacers, the efficacy of these low-molecular-weight displacers was shown to be dependent on both the initial carrier salt concentration and the displacer concentration. In addition to the fundamental interest generated by low-molecular-weight displacers, it is likely that these displacers will have significant operational advantages as compared with large polyelectrolyte displacers.