SEPARATION AND INDIRECT DETECTION OF AMINO-ACIDS BY REVERSED-PHASE ION-PAIR CHROMATOGRAPHY

Fourteen amino acids were successfully separated and indirectly detected (without the need for pre- or postcolumn derivatization) via reversed-phase ion-pair liquid chromatography. To improve retention and detection sensitivity, we used α-naphthylamine as the ion-interaction reagent and sodium heptane sulfonate as the hydrophobic counterion in the mobile phase. We studied the effects of the nature and concentration of the counterion and the ion-interaction reagent, the pH, and the ionic strength of the mobile phase on retention and sensitivity. For most amino acids, the detection limit was below the nanomole level. We observed a linear relationship between the injected amount of amino acids (up to 20 nmoles) and the peak area, with correlation coefficients of greater than 0.99. © 1993, Oxford University Press.