Photo-Stability of Cianidanol in Aqueous Solution and in the Solid State

Abstract

Cianidanol was exposed to light in aqueous solution and in the solid state for stability studies. Photo-decomposition of cianidanol occured by exposure to UV light below approximately 340 nm in aqueous solution and below approximately 310 nm in the solid state. In aqueous solution, photo-induced oxidation, which was liable to be remarkable with increasing pH value, and other photo-decomposition without participation of oxygen occured simultaneously. In the solid state, the photo-decomposition was inhibited by lowering the concentration of surrounding oxygen to below 0.1 % and cianidanol monohydrate was more stable to light than cianidanol tetrahydrate. Further, solid-state cianidanol exhibited remarkable coloration by exposure to light when mixed with magnesium alumina silicate and this coloration was inhibited by drying magnesium alumina silicate and removing water-soluble impurities contained in commercially available magnesium alumina silicate.