Photodegradation studies

The need to characterise and define light sources in photodegradation studies was outlined by investigators from the FDA [73]. They reported on UV-A-induced photolytic decomposition products of the anti-diuretics, chlorothiazide and hydrochlorothiazide. Both drugs are reported to be potent photosensitisers however, their photodegradation had previously been reported only under very specific conditions [74,75]. 

Durand, G., D. Barcelo, J. Albaiges, and M. Mansour (1990). Utilisation of liquid chromatography in aquatic photodegradation studies of pesticides A comparison between distilled water and seawater. Chromatographia, 29 120-124. 

Penuela, G.A. and D. Barcelo (2000). Comparative photodegradation study of atrazine and desethylatrazine in water samples containing titanium dioxide/hydrogen peroxide and ferric chloride/hydrogen peroxide. J.A.O.A.C. Int., 83 53-60. 

An interesting outcome of photodegradation studies on polymers is the finding that tensile and shear stress can accelerate the rate of photochemical degradation.9,19,63 For example, recent studies of this phenomenon showed... 

Table 10.7 Synthesis of results (photoproduction rates of NH4+ and DFAA) from this and other DOM photodegradation studies that emphasize nitrogen dynamics. 

Moore DE (1996) Standardization of Photodegradation Studies and Kinetic Treatment... 

As reported by Bansal et al. [12], glimepiride was stable to dry heat (50 °C for 31 days) since no decreasing of glimepiride peak area was observed. Similar result was also showing by photodegradation study. Exposure of 1.2 million lux hour fluorescent and 200 Wh/m of UV-A... 

Moore DE. Principles and practice of drug photodegradation studies. J Pharm Biomed Anal 1987 5 441 55. 

Moore DE. Standardization of photodegradation studies and kinetic treatment of photochemical reactions. In Tonnesen HH, ed. The PhotostabUity of Drugs and Drug Formulations. 1st ed. London Taylor and Francis, 1996 63-82. 

A critical aspect of the design and execution of meaningful (and reproducible) pharmaceutical photostability studies involves the presentation of the samples being tested to the photon source. Different considerations need to be made for forced photodegradation studies and confirmatory photostability studies. The choice of... 

The main focus of this chapter is on two well-studied series of photochromic compounds, spiropyrans and spirooxazines, and the comparison of their photo-reactive excited states and molecular structures. The discussion of their photodegradation takes into account the results obtained from spectrophotometric measurements together with the identification of the fragments resulting from photodegradation. Different mechanisms are proposed for the photooxidation reaction. The experimental apparatus and procedures for photodegradation studies are also described. 

G. Baillet, G. Giusti, and R. Guglielmetti, Comparative photodegradation study between spiro[indo-line-oxazine] and spiro[indoline-pyran] derivatives in solution, 7. Photochem. Photobiol. A 70 157— 161 (1993). 

Whilst the dimer, bis(3,4-mcthylcnedioxy-6-propy] benzene Jet her. was observed in soil photodegradation studies, it occurred in both irradiated soil and the dark control. The product was not seen in other soil studies, so if it were formed it must have been very rapidly degraded to undetectable levels. 

Fabric. A plain weave fabric (Testfabrics 361) made from spun, delustered nylon 6,6 was used in this study. The fabric was chosen because it was representative of the type of nylon fiber used outdoors and the type of fabric used in previous photodegradation studies (21-23). 

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