Hydrogen peroxide oxidation indices

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). 

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 2.5 Wroblowa s oxygen electroreduction mechanism with electrochemical rate constants k3 forthe direct reduction to water, k2 and k 2 for the parallel electrochemical reduction and oxidation of adsorbed hydrogen peroxide, k3 for the electrochemical decomposition of hydrogen peroxide to water, k4 for the chemical catalytic decomposition of hydrogen peroxide to oxygen, and ks and fc 5 for the parallel adsorption/desorption of the adsorbed hydrogen peroxide. The species with the super index and ° are located at the interface and in the bulk of the solution, respectively. The sub index ads refers to the adsorbed state, and 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. 

Polyvinyl alcohol oxidation affected by hydrogen peroxide in the presence of ferrous sulfate (II) in aqueous solutions is accompanied by chemiluminescence in the visible spectrum (Fig. 23.6). In Fig. 23.6, it is seen that luminous intensity passes through a maximum. This facts shows that luminescence emitter is an intermediate product of liquid-phase PVA oxidation. The analysis of the kinetic curve of chemiluminescence intensity showed that its initial part is well linearized (Fig. 23.6, the correlation index r = 0.998) in the equation coordinates... 

Properties Clear colorless sympy llq., odorless, sweet taste sol. in water, alcohol insol. in ether, benzene, chlotofonn m.w. 92.09 dens. 1.26201 (25/25 C) m.p. 17.8 C b.p. 290 C (dec ) flash pt. (OC) 176 C ref. index 1.4730 (25 C) Toxicology LD50 (oral, rat) > 20 ml/kg, (IV, rat) 4.4 ml/kg poison by subcut. route mildly toxic by ing. human systemic and Gl effects by Ing. skin and eye IrrIlanI nuisance dust human mutagenic data TSCA listed Precaution Combustible liq. exposed to heat, flame, strong oxidizers highly explosive with hydrogen peroxide ignites on contact with calcium hypochlorite explosive mixts. and violent reactions possible with many chems. 

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