Ultraviolet photo-oxidation

Ultraviolet photo-oxidation techniques can be used as a method for organic nitrogen. The organic nitrogen compounds are oxidised to nitrate and nitrite then determined by the standard seawater analysis methods [17,18,23]. 

Both the persulfate and ultraviolet oxidation methods have much to recommend them. Ultraviolet photo-oxidation methods have an advantage in that they are easily automated. 

Comparison of Results Obtained by Evaporation-Dry Combustion and Ultraviolet Photo-oxidation... 

Skjemstad, J. O., Janik, L. J., Head, M. J., and McClure, S. G. (1993). High energy ultraviolet photo-oxidation a novel technique for studying physically protected organic matter in clay- and silt-sized aggregates. J. Soil Sci. 44,485-499. 

Skjemstad, J.O. et al., High energy ultraviolet photo-oxidation A novel technique for studying physically protected organic matter in clay and silt-sized particles, J. 

Degradation of polyolefins such as polyethylene, polypropylene, polybutylene, and polybutadiene promoted by metals and other oxidants occurs via an oxidation and a photo-oxidative mechanism, the two being difficult to separate in environmental degradation. The general mechanism common to all these reactions is that shown in equation 9. The reactant radical may be produced by any suitable mechanism from the interaction of air or oxygen with polyolefins (42) to form peroxides, which are subsequentiy decomposed by ultraviolet radiation. These reaction intermediates abstract more hydrogen atoms from the polymer backbone, which is ultimately converted into a polymer with ketone functionahties and degraded by the Norrish mechanisms (eq. 

Agemian and Chau [55] have described an automated method for the determination of total dissolved mercury in fresh and saline waters by ultraviolet digestion and cold vapour atomic absorption spectroscopy. A flow-through ultraviolet digester is used to carry out photo-oxidation in the automated cold vapour atomic absorption spectrometric system. This removes the chloride interference. Work was carried out to check the ability of the technique to degrade seven particular organomercury compounds. The precision of the method at levels of 0.07 pg/1, 0.28 pg/1, and 0.55 pg/1 Hg was 6.0%, 3.8%, and 1.00%, respectively. The detection limit of the system is 0.02 pg/1. 

Photo-oxidation was seen as a possible route to a total phosphorus method. Again, early work on the method was done by Armstrong et al. [15] and Armstrong and Tibbitts [36]. Grasshoff [37] adapted the method to continuous automatic analysis a variation on this method is considered the standard method for automatic analysis today [18]. Bikbulatov [38], on the other hand, feels that such important phosphorus compounds as ATP and DI are not completely decomposed by ultraviolet irradiation and that persulfate oxidation gives better results. 

This type of degradation can also be referred to as photodegradation or ultraviolet (UV) degradation. It includes photo-oxidation. It produces some of the more familiar signs of degradation of plastics embrittlement, discoloration and loss of transparency. 

Particle mobility and zeta potential can now be measured by more sophisticated techniques. With photoelectrophoresis, particle mobility is measured as a function of pH under the influence of ultraviolet radiation. At pH < 8, the electrophoretic mobility of irradiated hematite particles (A = 520 nm) was markedly different from that measured in the absence of UV irradiation. This was attributed to the development of a positive surface charge induced by photo-oxidation of the surface Fe-OH° sites to (Fe-OH) sites (Zhang et al., 1993). The electroacoustic technique involves generation of sound waves by the particles in the colloidal dispersion and from this data. 

Ultraviolet Radiation The portion of the electromagnetic spectrum emitted by the sun adjacent to die violet end of die visible light range. Often called black light , it is invisible to the human eye but when it falls on certain surfaces it causes them to fluoresce or emit visible light responsible for the photo-oxidation of certain compounds including hydrocarbons. 

Armstrong, F. A. J., Williams, P. M., and Strickland, J. D. H. (1966). Photo-oxidation of organic matter in seawater by ultraviolet radiation, analytical and other applications. Nature 211, 481 183. 

Our immediate need was to develop a more elegant way of stabilizing the images that were made by photo-oxidation of leucodyes. One obvious way was to truncate the absorption spectrum of HABIs, so that the activation occurred only in the ultraviolet region—at wavelengths <380 nm. Despite a significant synthetic effort, this was not accomplished. The spectra of a number of HABIs are shown in Figure 4.1. 

Methacrylates are exceptionally stable to ultraviolet (UV) light and to oxygen owing to the absence of tertiary hydrogens on the polymer chain which prevent photo-oxidative and thermo-oxidative attack. Acrylate ester polymers are somewhat less resistant to both UV light and thermal oxidation owing to the presence of tertiary hydrogen atoms. 

In vitro studies have demonstrated that. vera latex derived anthraquinones in presence to ultraviolet light A (UVA) exhibited significant photo-oxidative damage to both cellular RNA and DNA 61). Several studies on photostability and phototoxicity of A vera extracts indicate that in presence of UV light it can generate the formation of free radicals 62, 63). 

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