FLOW-INJECTION AND LIQUID-CHROMATOGRAPHIC POSTCOLUMN DETECTION OF AMINO-ACIDS BY MIMETIC PEROXIDASE-CATALYZED CHEMILUMINESCENCE REACTION

Four amino acids were determined on the basis of the finding that the catalytic activity of mimetic peroxidase (metalloporphyrin) in the chemiluminescence reaction between luminol and hydrogen peroxide is inhibited in the presence of an amino acid. The degree of chemiluminescence inhibition is a measure of the amino acid concentration. The electrostatic interaction between amino acid and metalloporphyrin was confirmed by comparing the degree of inhibition of cationic and anionic metalloporphyrin-catalysed chemiluminescence reactions. More than 20 amino acids were tested, and only L-cysteine, L-tyrosine, L-tryptophan and L-cystine significantly quenched the chemiluminescence intensity. Detection limits were 6.8 X 10(-8), 1.3 X 10(-7), 8.5 X 10(-6) and 2.2 X 10(-5) M, respectively. The detection approach is demonstrated with a silica-based liquid chromatographic separation of amino acids using phosphate buffer (pH 7.3) as mobile phase. Compared with other chemiluminescence analyses, this method is faster, can be run at room temperature and, in favourable cases, has a lower detection limit.