PHOTOSENSITIZED BLEACHING OF β‐CAROTENE WITH LIGHT AT 632·8 nm FROM A CONTINUOUS‐WAVE GAS LASER

Abstract

Abstract— β‐Carotene was not affected when irradiated with a monochromatic beam of light (632·8 nm) from a continuous‐wave gas laser. However, β ‐carotene undenvent numerous changes when irradiated in the presence of the photosensitizing dye toluidine blue. Initially there was a considerable decrease in the absorbance of the β‐carotene, accompanied by small shifts of the absorption maxima to shorter wavelengths as well as the formation of two new peaks at 400 and 375 nm. Ultimately a complete bleaching of the solution was observed. By the use of column and thin layer chromatography up to 13 different compounds including cis‐isomers, epoxides and possibly hydroxy compounds were shown to be formed by the photosensitization of the β‐carotene. These reactions were found to be oxygen‐dependent.