Use of Triethylamine as an Ion-Pairing Reagent

Evidence that triethylamine (TEA) functions as an ion pairing reagent (IPR) in a mobile phase system (20 mmol/L acetic acid, 20 mmol/L phosphoric acid, 30 mmol/L TEA, pH 7.0) under both gradient and isocratic elutions is presented. The retention of anions (nicotinic, xanthurenic, anthranilic, and 3-hydroxyanthranilic acids) was increased with increasing TEA (cations) concentration; that of cations (benzylamine) was decreased and that of zwitterions or neutrals (kynurenine, 3-hydroxykynurenine, and aniline) exhibited no changes. TEA is shown to be a useful IPR in gradient elution due to its rapid equilibration time with the column. Proper selections of detection wavelength and gradient program are important to eliminate the interference of impurities in many commercial TEA preparations.