PHOTOCHEMICAL STABILITY OF SULPHORHODAMINE-B

Commercially available and purified samples of Sulphorhodamine B in aq ueous solution appeared to be photostable over a range of pH when subj ected to simulated sunlight. The compound was degraded, however, in th e presence of hydrogen peroxide (100 vol.), the reaction following fir st order kinetics. Inclusion of mannitol into this mixture greatly inc reased the rate constant. Further addition to the mixture of acetaldeh yde rendered the dye non-photodegradable, suggesting that its breakdow n with hydrogen peroxide was hydroperoxy radical mediated. The latter reaction was strongly affected by the wavelength of light impinging on the reactants.