The binding affinity of uncharged aromatic solutes for negatively charged resins is enhanced by cations via cation–π interactions: The case of sodium ion and arginine

Salt solutions are widely used as eluents for ion-exchange chromatography. In general, salts reduce the retention of applied solutes on ion-exchange columns via electrostatic screening effects. The reverse phenomenon, namely, salt-enhanced retention, has not been reported. Here, we report that cations, including arginine, guanidine and sodium ions, enhance the retention of uncharged aromatic solutes on a cation-exchange resin, i.e., a negatively...