Chemiluminescence behavior of the decomposition of hydrogen peroxide catalyzed by copper(II)–amino acid complexes and its application to the determination of tryptophan and phenylalanine Original Research Article

A weakly chemiluminescent (CL) emission has been observed during the decomposition of hydrogen peroxide catalyzed by copper(II) in basic aqueous solution. On adding an appropriate amount of amino acid solution into the mixed solution of hydrogen peroxide and copper(II), a strong CL emission was recorded. This CL emission depends on the kind of amino acid. The CL emissions for tryptophan and phenylalanine were fast, but for other amino acids, they were relatively slow. In the presence of a low concentration of carbonate in the basic solution, the CL emission was enhanced for all amino acids. This CL system was developed for the determination of amino acids with a flow injection system. The detection limits of tryptophan and phenylalanine were 4.5 × 10−6 and 1.1 × 10−5 M, respectively. After the liquid chromatographic separation of tryptophan and phenylalanine by means of an ODS-80Ts column (5 μm, 250 mm × 4.6 mm i.d.) with water as eluent, the present CL system was used as a post-column detector for these two amino acids in tablets without any special labeling treatment.