Photodegradation solution

The antibacterial activity of curcumin is greatly enhanced by UV-VIS radiation (5). Photodegraded solutions of thiomerosal were found to be more active... 

The process by which a solubility differential between exposed and unexposed areas occurs is well known (74). Photodegradation products of the naphthoquinone diazide sensitizer, eg, a l,2-naphthoquinonediazide-5-sulfonic acid ester (11), where Ar is an aryl group, to an indene carboxylic acid confers much increased solubility in aqueous alkaline developer solutions. 

Studies have appeared where photolysis in natural bodies of water under normal sunlight conditions has been examined. For example, metolachlor was slowly photodegraded by sunlight in lake water, with a half-life of 22 days in summer and 205 days in winter (28). Addition of a 5% solution of dissolved organic matter to the water extended the half-Hves two to three times longer, depending on the season (see PHOTOCHEMICAL TECHNOLOGY, photocatalysis). ... 

Topochemical [24-2] photoreactions of diolehn crystals has been reviewed. The reactions clearly depart from typical solution chemistry crystal-lattice control offers a unique synthetic route into photodegradable polymers, highly strained [24-2] paracyclophanes, stereoregular polymers, and absolute asymmetric synthesis. However, achieving the desired type of crystal... 

Carey JH, ME Cox (1981) Photodegradation of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM). 1. Pathway of the direct photolysis in solution. J Great Lakes Res 7 234-241. 

Smith AE, J Grove (1969) Photodegradation of diquat in dilute aqueous solution and on silica gel. J Agric Food Chem 1 609-613. 

The purified sulfuric acid (i.e., preheated the commercial ultrapure grade H2SO4 at 200°C for 24 hr under vacuo to remove its decarboxylating contaminants and subsequently cooled to ambient temperature), 0.5 ml, was added to the bottom well of the decarboxylation flask and subsequently placed under vacuo. A known amount of a GC-standard (640 mm of 100 ppm C2Hg in He) was introduced into the flask for the total CO2 determination. The acid was then allowed to dissolve the photodegraded residual film on the side of the flask by tilting. The acid solution was left standing for 20 minutes at room temperature. 

A dramatic example of photolysis is the photodegradation of sodium nitroprusside in aqueous solution. Sodium nitroprusside, Na2Fe(CN)5NO-2 H20, is administered by intravenous infusion for the management of acute hypertension. If the solution is protected from light it is stable for at least one year if exposed to normal room light, it has a shelf life of only 4 hours [35]. 

The main route for the photodegradation of the polymers 10 and 11 in the solid films in air consists of radical scission of the silicon-silicon bonds, analogous to that observed in solution, but in the films, the resulting silyl radicals react with oxygen to give... 

FIGURE 12.4 Lycopene photodegradation in 0.02 M Triton X-100 aqueous solutions illuminated with a 150 W (> 380 nm) filament lamp. Inset evolution of the difference absorption spectrum (AA). 

FIGURE 12.6 Comparison of photodegradation kinetics of bixin in aqueous solutions containing malto-dextrin (MD) under different conditions ( ) microencapsulated and (A) not encapsulated. (From Barbosa, M.I.MJ. et al., Food Res. Int., 38, 989, 2005. With permission.)... 

Chen Y, Hu C, Hu X, Qu J (2009) Indirect photodegradation of amine drugs in aqueous solution under simulated sunlight. Environ Sci Technol 43 2760-2765... 

Tang WZ, Zhang Z, An H, Quintana MO, Torres DF (1996) Ti02/UV photodegradation of azo dyes in aqueous solutions. Environ Technol 18 1-12... 

Wilhelm, P. and Stephan, D. (2007) Photodegradation of rhodamine B in aqueous solution via Si02 Ti02 nanospheres. Journal of Photochemistry and Photobiology A Chemistry, 185, 19-25. 

The photodegradation of PVCa solutions has been studied to determine a mechanism for the photodegradation process and identify the excited states involved. The polymer was secondary grade (Aldrich Chemical Company) that was further purified by reprecipitation three times from methylene chloride solution by the dropwise addition into methly alcohol. Solutions in methylene chloride were found to yellow rapidly in air upon exposure to 360 nm light, whereas solutions degassed by the freeze-pump-thaw technique showed little yellowing. 

---