Oxidation stabilisation against

Retard efficiently oxidation of polymers catalysed by metal impurities. Function by chelation. Effective metal deactivators are complexing agents which have the ability to co-ordinate the vacant orbitals of transition metal ions to their maximum co-ordination number and thus inhibit co-ordination of hydroperoxides to metal ions. Main use of stabilisation against metal-catalysed oxidation is in wire and cable applications where hydrocarbon materials are in contact with metallic compounds, e.g. copper. 

Impurities in other solvents may affect chromatographic behaviour, or detection, or both. Chlorinated solvents such as di- or trichloromethane are stabilised against oxidative breakdown by the addition of small amounts of methanol or ethanol. 

It was suggested that the role of the partly reducible metal oxide additive is to contribute to the formation of new active sites and increase N2O dissociation. On the other hand, alkali and alkaline earth metal oxides stabilise gold particles against sintering. 

In terms of stabilisation against discolouration, primary phenolic antioxidants exhibit some inhibition activity whereas combinations with phosphites can display powerful synergism. This is consistent with the involvement of a free radical oxidation process in deacetylation through ketone/hydroperoxide initiation. 

Polyolefins such as polyethylene and polypropylene contain only C—C and C—H bonds and may be considered as high molecular weight paraffins. Like the simpler paraffins they are somewhat inert and their major chemical reaction is substitution, e.g. halogenation. In addition the branched polyethylenes and the higher polyolefins contain tertiary carbon atoms which are reactive sites for oxidation. Because of this it is necessary to add antioxidants to stabilise the polymers against oxidation Some polyolefins may be cross-linked by peroxides. 

Oxidation reactions of fried food occur rather intensively on storage as the thin film of flying oil left on the surface of fried food is easily attacked by oxygen from the air. The stabilisation of fried food against oxidation on storage thus offers a more important problem than does oxidation during the flying operation. 

Nowadays, consumers would like those antioxidants present in food products not only to stabilise food lipids, but also to be absorbed through the intestinal wall and protect the lipids of blood plasma against oxidation. This effect is relatively evident in the case of tocopherols (which are liposoluble) or ascorbic acid (which is hydrophilic), but much less evidence is available on antioxidants of medium polarity, such as flavonoids, rosemary oleoresins or green or black tea catechins. 

Epididymis Carnitine Inositol Phosphatidylcholine Cholesterol Glycoproteins Facihtates acetyl-CoA oxidation by spermatozoa (Chapter 9) Precursor for formation of phosphatidyhnositol bisphosphate Buffer to maintain pH and a source of chohne Stabilises membranes They coat the surface of the sperm to protect against IgA... 

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