Chemiluminescence characterisation of the reaction system Tb(III)-amino acid-peroxynitrous acid

Chemiluminescence of the reaction system tryptophan-hydrogen peroxide-nitrite-Tb(III)-H2SO4 was used for the determination of tryptophan. The chemiluminescence intensity observed in the system tryptophan-hydrogen peroxide-nitrite-sulfuric acid, in the presence of Tb(III) ions was five times higher than that in a solution without Tb(III) ions. The chemiluminescence spectrum obtained for the system tryptophan-hydrogen peroxide-nitrite-sulfuric acid solution showed one band, with λmax ∼ 520 nm, whereas in the presence of Tb(III) ions two bands with λmax ∼ 520 nm and 550 nm were observed. The peak centered at ∼550 nm, corresponding to the 5D4 → 7F5 transition, which is typical for the Tb(III) ion. A linear dependence was found for the CL intensity versus the tryptophan concentration, in the range of 1.2 × 10−7 to 1 × 10−4 mol/l. Terbium(III) ions play the role of sensitizer in the reaction mixture tryptophan-hydrogen peroxide-nitrite-sulfuric acid.