Ruthenium (II) 1,10-Phenanthroline Salts as Mobile Phase Additives for the Separation and Indirect Detection of Free Amino Acids

Abstract

Ruthenium (II) 1,10-phenanthroline, Ru(phen)²⁺ ₃, salts are used as ion interaction reagents in a basic mobile phase for the retention, resolution, and indirect photometric detection (IPD) of free amino acids on a polystyrene divinylbenzene (Hamilton PRP-1) column. Mobile phase Ru(phen)²⁺ ₃ concentration and pH and type and concentration of organic modifier and counteranion affect retention and IPD. Underivatized amino acid elution order is influenced by side chain structure typical of ion exchange processes. Detection limits for the separation and detection of free amino acids using an isocratic elution condition are about 0.1 nmole for lower retained amino acids and 0.25 nmole for higher retained amino acids for a 3:1 signal:noise ratio. Gradient elution is possible but at higher detection limits.