Hydrogen peroxide 788 INDEX

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

Figure 10.28 Effect of temperature on the whiteness index of linen bleached using urea-activated hydrogen peroxide [243], Treated with 7 g/l hydrogen peroxide and 8 g/l urea for 150 min at pH 6 and 50 1 liquor ratio...

Figure 10.38 Effect of treatment time on the alkali solubility and Jaquemart whiteness index of wool bleached with 2-vol. hydrogen peroxide at 40 °C and 50 °C [259,264]...

Colquhoun and Schumacher [98] have shown that y-linolcnic acid and eicosapentaenoic acid, which inhibit Walker tumor growth in vivo, decreased proliferation and apoptotic index in these cells. Development of apoptosis was characterized by the enhancement of the formation of reactive oxygen species and products of lipid peroxidation and was accompanied by a decrease in the activities of mitochondrial complexes I, III, and IV, and the release of cytochrome c and caspase 3-like activation of DNA fragmentation. Earlier, a similar apoptotic mechanism of antitumor activity has been shown for the flavonoid quercetin [99], Kamp et al. [100] suggested that the asbestos-induced apoptosis in alveolar epithelial cells was mediated by iron-derived oxygen species, although authors did not hypothesize about the nature of these species (hydroxyl radicals, hydrogen peroxide, or iron complexes ). 

Cleaning of SPR glass slides (optical grade SF2, refractive index 1.65, from UQG Optical Components). Sonicator (e.g., Lucas Dawe sonication bath) and different solutions hydrochloric acid/nitric acid 3 1 v/v (solution A) ammonium cerium nitrate (1M) (solution B) sulfuric acid/hydrogen peroxide 1 1 (Piranha solution) isopropanol. Use caution in handling these solutions harmful and corrosive. 

Index Entries Pretreatment newspaper ammonia hydrogen peroxide enzymatic digestibility surfactant. 

Figure 1.17 Refractive index range of hydrogen peroxide-water mixtures.

Bleaching of wool is necessary for the enhancement of whiteness and lustre. Using proteolytic enzymes alone [99] or in combination with peroxide [100], the degree of whiteness and hydrophilicity of the fibres are increased, comjjared with the oxidative treatment alone [99]. Serine protease stable to hydrogen peroxide is active in an alkaline medium and its activity increases with increasing peroxide level [94]. Higher whiteness index is caused by the decolourising action of the enzyme on natural colorants present in the wool fibre [100]. 

SCHEME 2.4 Damjanovic s oxygen electroreduction mechanism with three electrochemical rate constants ki for the direct reduction to water, f°r the parallel formation of adsorbed hydrogen peroxide, and k3 for the electrochemical decomposition of hydrogen peroxide to water. The species with the super index and 0 are located at the interface and in the bulk of the solution, respectively. The term dif symbolizes the diffusion to the bulk of the solution and vice versa. 

The term C, is the 20% index at time t and represents the amount of cleaved disulfide at time f is the 20% index at time zero and represents the total amount of disulfide before oxidation and a represents the fiber radius, assumed to be 40 pm. Considering these assumptions, one obtains an approximate diffusion coefficient of 1.8 x lO cm /min. This diffusion coefficient is of the anticipated magnitude, suggesting that the oxidation of the disulfide bond in hair by alkaline hydrogen peroxide is a diffusion-controlled reaction. 

One of the most interesting and important species in air is hydrogen peroxide (H2O2). Kok et al. (1978) suggested that H2O2 is an index of the HO2 radical concentration and better represents oxidation capacity than ozone. However, the relatively complicated and labor-intensive measurement technique hmits H2O2 measurements to very few sites and even then only occasionally (probably because of fixing to ozone as the oxidant leader species). 

Since the entire transformation is hyperhypsic, a net reduction has occurred. This corresponds to one of the oxygen atoms in hydrogen peroxide that is being reduced. The sulfur atom in sodium bisulfite is oxidized to sodium bisulfate, but since the sodium bisulfite reagent is a sacrificial one the oxidation number change at sulfur does not count in the calculation of the hypsicity index. 

Simms et a/. [76] recently used ATRP of nBMA in the miniemulsion systems, using a redox initiation system (ascorbic acid/ hydrogen peroxide) with a CuBr /EHAb-TREN catalyst. A high MW was obtained with Mn=10 g/mol (number average molecular weight) and polydispersity index (PDI)=1.25. In addition, the conversions above 80% were achieved in 8 h, as well as the particle size of 100 nm. 

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