Photochemical degradation sunlight

Photodegradation. The photochemical degradation products of diflubenzuron in strictly aqueous solution are unreported, perhaps because of the compound s refractory solubility. Exposure of thin films on glass or a 0.1 ppm aqueous solution to sunlight... 

Ascorbic acid (0.8% w/v) in aqueous solution degraded according to apparent first order kinetics, with a rate constant of 2.34 x 10 2/hour, when irradiated by artificial sunlight [40]. The presence of 5% aspartame in the solution decreased the rate constant to 1.48 x 10 2/hour, thus stabilizing ascorbic acid to photochemical degradation by about 37%. Similar effects were also seen with some carbohydrate sweeteners. 

Natural fibers may be adversely affected by sunlight, air pollutants, acids and alkali, bleaches and other oxidizing agents, and chemical finishing processes. However, the effects of photochemical degradation are by far the most problematic in the conservation of textiles and therefore have received the most attention. 

Direct photochemical degradation of 1,1,1-trichloroethane in the troposphere is not expected to be an important fate process, because there is no chromophore for absorption of ultraviolet light (>290 nm) found in sunlight at tropospheric altitudes (Hubrich and Stuhl 1980 VanLaethem-Meuree et al. 1979). A laboratory experiment performed in sealed Pyrex ampules showed loss of 1,1,1-trichloroethane in 2 weeks under the influence of sunlight however, catalysis by the Pyrex surface was probably responsible for the enhanced reactivity (Buchardt and Manscher 1978). 

Sunlight and ultraviolet light have been shown to decrease the 15% index (in distilled water). This effect relates to the total radiation on the hair [58]. These findings were interpreted as photochemical degradation of disulfide bonds and have been confirmed by Robbins and Kelly [59]. This work involved analysis of amino acids of both proximal and distal ends of human hair where a significantly larger amount of cysteic acid and a significantly smaller amount of cystine were found in distal ends. Harris and Smith [60] have provided evidence for ultraviolet disruption of cystine in wool. 

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