Photostability of solid-state ubidecarenone at ordinary and elevated temperatures under exaggerated UV irradiation.

The photostability of ubidecarenone was investigated. Two irradiation apparatus, a grating monochromator and a high-pressure mercury vapor lamp, were employed at ordinary and elevated temperatures. Both physicochemical and chemical stabilities were significantly affected by irradiation wavelength, with UV light causing the greatest changes. The degree of degradation was a function of the light absorption properties of the substrate and markedly increased when the absorption became greater than 30%. The photolytic degradation followed apparent first-order kinetics at all wavelengths and was promoted with temperature elevation. The Arrhenius plot gave an activation energy in the solid state different from that in the liquid state. These activation energies linearly decreased with increasing intensity of UV light.