Antioxidant Degradation

The silica gel corresponding to each of the six observed bands was then separately scraped off from the plate and reheated with absolute ethyl alcohol to desorb the organic matter. The six extracts, obtained were then prepared into potassium bromide micro-discs and examined by IR spectroscopy in the 2.5-15 pm range. The results suggested that upon milling into PE at 260 C, Santonox R degrades into at least two products, i.e., a phenolic breakdown product (band 2) and non-phenolic hydrocarbon (band 4). The phenolic breakdown product (band 2) has some resemblance to the material produced upon heating Santonox R in air for 30 minutes at 250 C. 

Excess ferric ions react with Santonox R but not with the oxidation products to produce ferrous ions which can then be determined by the spectrophotometric 2,2 -dipyridyl method, giving an estimate of the unoxidised Santonox R content of the extract  

Other polymers that have been examined by EGA include polyvinylchloride (PVC) [17-19], polystyrene [20-23], styrene-acrylonitrile copolymers [24-26], PE and PP [27-32], polyacrylates and their copolymers [33-36], and polyethylene terephthalate, polyphenylenes, and polyphenylene oxides and sulfides [36-41]. Studies involving the use of chromatography include the thermal degradation of PVC [42], vinyl plastics [43] and polysulfone [44], 

Muezelaar, J. Haverkamp and ED. Hileman, Pyrolysis Mass Spectroscopy of Recent and Fossil Biomaterials, Elsevier, Amsterdam, The Netherlands, 1982. 

Yamada, T. Oura and T. Haruki in Proceedings of the International Conference of Thermal Analysis, Budapest, Hungary, 1974, Part 3, p.l029. 

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Phospholipid hydrolysis Cholesterol autooxidation Antioxidant degradation Physical stability Vesicle size distribution submicron range... 

One of the drawback of radiation crosslinking of NR latex is the poor ageing property of the film. This poor ageing property may be coming from two causes natural antioxidant degrade under radiation and autoxidation due to the presence of trapped radical in NR matrix. 

Unlike some of the other common test methods, the XRF technique does not provide any structural information about the antioxidants detected. In addition to the total concentration, chromatographic and infrared based methods can also provide information on the degree of antioxidant degradation products (such as the phosphate content, which is the oxidized form of phosphite antioxidants, normally created during polymer processing). The XRF technique also has limited utility when more than one phosphite or thioester antioxidant is present in the sample, because the total phosphorus or sulfur concentration does not provide the degree of distribution from each antioxidant. 

Localized Antioxidant Degradation in Relation to Promotion of Lipid Oxidation... 

In conclusion, monitoring antioxidant degradation in localized areas of tissue can prove useful as a marker for the onset of a product s quality loss. The multifaceted protection available to biological membranes, though, would suggest that measurements of more than one antioxidant are warranted during storage. 

While the examples presented in this chapter were from model system incubations, similar valuable information will be obtained by monitoring antioxidant degradation in specific membrane fractions from stored tissue. 

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