Absorption oxidative degradation

Analysis of Trace or Minor Components. Minor or trace components may have a significant impact on quaHty of fats and oils (94). Metals, for example, can cataly2e the oxidative degradation of unsaturated oils which results in off-flavors, odors, and polymeri2ation. A large number of techniques such as wet chemical analysis, atomic absorption, atomic emission, and polarography are available for analysis of metals. Heavy metals, iron, copper, nickel, and chromium are elements that have received the most attention. Phosphoms may also be detectable and is a measure of phosphoHpids and phosphoms-containing acids or salts. 

Revised structures have been proposed for these compounds. The brownish-yellow acid obtained with maleic anhydride has been shown by ultraviolet, infrared, and nuclear magnetic resonance absorption measurements and oxidative degradation to have the tricyclic structure... 

The oxidative degradations of binuclear azaarenes (quinoline, isoquinoline, and benzodrazines) by hydroxyl and sulfate radicals and halogen radicals have been studied under both photochemical and dark-reaction conditions. A shift from oxidation of the benzene moiety to the pyridine moiety was observed in the quinoline and isoquinoline systems upon changing the reaction from the dark to photochemical conditions. The results were interpreted using frontier-orbital calculations. The reaction of OH with the dye 3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-(l,8)(2//,5//)-acridinedione has been studied, and the transient absorption bands assigned in neutral solution.The redox potential (and also the pA a of the transient species) was determined. Hydroxyl radicals have been found to react with thioanisole via both electron transfer to give radical cations (73%) and OH-adduct formation (23%). The bimolec-ular rate constant was determined (3.5 x lO lmoU s ). " ... 

Extremely inhomogeneous conditions are found in oxidative degradation processes induced by vacuum ultraviolet (VUV) irradiation of aqueous reaction systems. In fact, the absorption cross section of water for an almost monochromatic excitation at 172 nm (Xe excimer lamp, vide infra) being very... 

After a short period of use in the average engine, changes start to occur. Initially, a loss of the zinc based antiwear/antioxidant additive ZDDP is observed by negative absorptions at 1000 cm 1 and 715 cm 1. Oxidative degradation of oil follows soon after and this is observed by positive absorptions, represented by carbonyl, hydroxy, nitro and C-O- species. The ER spectroscopy of lubricants can reflect additive depletion and the formation of oxidation products (Coates and Setti, 1984 Coates etal., 1984). 

In proving the structure of the anhydro compound, Huebner, Lohmar, Dimler, Moore, and Link22 established first the presence of the benzimidazole moiety through its ultraviolet absorption spectrum and through its oxidative degradation by permanganate to 2-benzimidazole-... 

Formation of zero-valent copper clusters with glutathione has been studied anaerobically. The ligand has been reported to provide a snbstantial degree of surface passivation. Rednction of a Cu(II)-GSH complex prodnced nanoparticles with a plasmon resonance band at 363 nm. These nanoparticles possessed a diameter of 9.7 4.3nm as demonstrated by TEM analysis. Under aerobic conditions, the nanoparticles oxidatively degrade as evinced by the loss of the plasmon absorption band over time. 

Several workers have reported on the changes in IR spectra with heating time during termo-oxidative degradation (13). No report on the temperature dependence could be found, however. Our results on this question demonstrated an almost identical pattern of changes in both the hydroxyl-, carbonyl- and ether-absorption... 

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