Displacement chromatography has attracted signifcant attention as a powerful technique for the purification of bioherapeutic proteins and oligunucleotides. Displacement chromatography enables simultaneous concentration and purification in a single step, which is significant in the purifcation of biopharmaceuticals. However, the major obstacle in implementing this technique is the lack of a sufficient diversity of appropriate displace candidates that are applicable across a wide spectrum of bioseparation demands. This invention is directed to methods of modifying amunoglycosides with linear polyamines to construct a library of candidates for use as high affinity cation-exchange displacers. These candidates are superior in binding to other known displacers, and they can be used in extremely low concentrations, increasing the purity and resolution of the target protein. Additionally, using these diplacers in displacement chromatography concentrates the target protein rather than diluting it (as most other chromatography methods do).