A tridentate ligand, trimethoxysilylpropyldiethylenetriamine, was bound to silica and studied as a stationary phase for reversed-phase ligand-exchange chromatography. The tridentate stationary phase “triamine” yielded more stable metal complexes, i.e., better metal loading efficiencies than previously reported diamine and monoamine stationary phases. This triamine packing with its enhanced metal loading properties was evaluated to identify the key factors that effect solute retention and selectivity. Mobile phase properties like buffer ionic strength and metal concentration greatly affected retention, while type of metal, i.e., Zn II, Cd II, Hg II, Cu II, or Ni II greatly affected selectivity. The choice of mobile phase organic modifier signigicantly affected both retention and selectivity. Methanol—water mobile phases elicited relatively little metal binding per triamine site, with Hg II, Zn II, Ni II and Cd II occupying 32, 9.5, 7.8 and 5.7, respectively. Changing the organic modifier from methanol to acetonitrile provoked a dramitically different but consistent pattern of metal loading to the triamine. The ratio of loaded metal with the acetonitrile modifier was 2.3 ± 0.1 fold higher than that observed for the methanol modifier in each of the cases tested. Factors found to affect metal loading to the stationary phase were the type of metal and the mobile phase solvent. The loading of metals onto the silica-bound triamine correlated directly to metal basicity. The variety of solute selectivities obtained in this study indicate that the key solute—metal interactions are a function of metal and solute functional group basicities and the number and spacing of solute functional groups possessing lone-pair electrons capable of interacting with the metal. Retention can be greatly enhanced when multiple functional groups possessing donatable electrons are present: functionalities containing nitrogen, sulfur or oxygen. Ring-substituted nitrogen, sulfur or oxygen atoms i.e. piperdines, pyrimidines, purines, xanthines and triazoles, enhance retention more than non-ring-substituted functionalities, such as carboxylic and sulfonic acids. The presence of non-electron-donating functionalities in close proximity to strong interacting groups resulted in significant decreases in retention due to steric hindrance of solute lone-pair electrons to the metal coordination sphere. It is suggested that the mechanism of ligand-exchange retention on this triamine phase involves the reversible binding of a metal to the stationary phase followed by outer-sphere solute—metal complexation.