Separation of 18 6-aminoquinolyl-carbamyl-amino acids by ion-pair chromatography.

Eighteen 6-aminoquinolyl-carbamyl (AQC)-amino acids were separated by ion-pair chromatography, using tetrabutylammonium (TBA) as a counterion. Optimum separation was obtained on a C8 reverse-phase column using gradient elution with two mobile phases, A (5 mM TBA, 75 mM ammonium acetate, pH 7.5) and B (80% acetonitrile). The AQC-amino acids were detected by fluorescence with excitation at 250 nm and emission at 395 nm, and the analysis time was 65 min. The response factors of individual AQC-amino acids to AQC-phenylalanine ranged from 0.42 to 1.08 (except for tryptophan at 0.01), with an average of 0.8. Detection limits by fluorescence ranged from 11.8 fmol (threonine) to 51.7 fmol (methionine), except for tryptophan (1.8 pmol).