Radiolysis of azo dyes in aqueous solution: Apollofix Red

The UV-Vis absorption spectra of azo dyes in aqueous solutions strongly overlap with the spectra of intermediates produced in the reaction of these dyes with the intermediates of water radiolysis. This overlap complicates the investigation of reaction mechanisms. The paper describes a method for the separation of the two spectra on the example of Apollofix Red, a triazine and H-acid containing dye. The reactivity of water radiolysis intermediates (e⁻_aq, ^˙OH, ^˙H, ^˙O⁻₂/HO^˙₂) with the dye is also discussed. The most intensive discolouring was found in the reaction of e⁻_aq and ^˙H, which is due to the fast reaction of these intermediates with the azo group of the unreacted molecule, and their slow reaction with the transformed molecules.