Oxidation products, analysis

Since aldehydes are very common amongst periodate-oxidation products, analysis for them has been well developed and widely used. Most emphasis has been placed on methods for the assay of formaldehyde, as this is the most common product. Formaldehyde was first determined (in periodate work) by an oxidation method.2 47 66... 

Thiobarbituric acid (TBA), secondary lipid oxidation products analysis, 535... 

Dutta, P.C., Savage, G.P. 2002. Harmonization of cholesterol oxidation product analysis. In Cholesterol and Phytosterol Oxidation Products Analysis, Occurrence, and Bological Effects (F. Guardiola, P.C. Dutta, R. Codony, G.P. Savage, eds.), pp. 114-123, AOCS Press, Champaign, IL. 

Stanton, C., Devery, R. 2002. Formation and content of cholesterol oxidation products in milk and dairy products. In Cholsterol and Phytosterol Oxidation Products Analysis,... 

P. Corti, G. Corbini, E. Dreassi, N. Politi, and L. Montecchi, Thin layer chromatograohy in the quantitative analysis of drugs—determination of rifaximine and its oxidation products, Analysis, 79 257 (1991). 

Kinter, M. Analytical technologies for lipid oxidation products analysis. J. Chromatogr. B 671, 223-236 (1995)... 

Oxidation product analysis by GLC shows that the only dibenzyl ether oxidation product is benzaldehyde At the same time during the oxidation process small amounts of benzyl alcohol are detected in the reaction media Benzyl alcohol oxidation rate is five times higher than that for dibenzyl ether. The form of kinetic curves for benzyl alcohol oxidation is typical for intermediate products in consecutive processes. It must be emphasized that the benzyl alcohol formation is not a result of hydrolysis. Furthermore it was established that in early stages of oxidation both products benzaldehyde and dibenzyl ether are formed simultaneously. All these data obtained proved consecutive dibenzyl ether oxidation followed ... 

Nitration results from fuel combustion in engines. The products formed are highly acidic and they may leave deposits in combustion areas. Nitration will accelerate oil oxidation. Infrared analysis is used to detect and measure nitration products. 

Although Ce(IV) oxidation of carboxylic acids is slow and incomplete under similar reaction conditions , the rate is greatly enhanced on addition of perchloric acid. No kinetics were obtained but product analysis of the oxidations of -butyric, isobutyric, pivalic and acetic acids indicates an identical oxidative decarboxylation to take place. Photochemical decomposition of Ce(IV) carbo-xylates is highly efficient unity) and Cu(ll) diverts the course of reaction in the same way as in the thermal oxidation by Co(IIl). Direct spectroscopic evidence for the intermediate formation of alkyl radicals was obtained by Greatorex and Kemp ° who photoirradiated several Ce(IV) carboxylates in a degassed perchloric acid glass at 77 °K in the cavity of an electron spin resonance spectro-... 

Quantitative analysis can be carried out by chromatography (in gas or liquid phase) during prolonged electrolysis of methanol. The main product is carbon dioxide,which is the only desirable oxidation product in the DMFC. However, small amounts of formic acid and formaldehyde have been detected, mainly on pure platinum electrodes. The concentrations of partially oxidized products can be lowered by using platinum-based alloy electrocatalysts for instance, the concentration of carbon dioxide increases significantly with R-Ru and Pt-Ru-Sn electrodes, which thus shows a more complete reaction with alloy electrocatalysts. 

Yeom and Frei [96] showed that irradiation at 266 nm of TS-1 loaded with CO and CH3OH gas at 173 K gave methyl formate as the main product. The photoreaction was monitored in situ by FT-IR spectroscopy and was attributed to reduction of CO at LMCT-excited framework Ti centers (see Sect. 3.2) under concurrent oxidation of methanol. Infrared product analysis based on experiments with isotopically labeled molecules revealed that carbon monoxide is incorporated into the ester as a carbonyl moiety. The authors proposed that CO is photoreduced by transient Ti + to HCO radical in the primary redox step. This finding opens up the possibility for synthetic chemistry of carbon monoxide in transition metal materials by photoactivation of framework metal centers. 

The oxidizing agent (organic peracid) usually attacks the sulfur from the less hindered side of the substrate to produce the less hindered oxidation product as a major isomer Thus, the observed stereoselectivity means the exclusive formation of the rmti-isomer (a). This conclusion was confirmed by NMR analysis (see Section III.B.4.b) and, clearly, can be extended and generalized with respect to larger cyclic sulfoxide systems. 

Studies conducted by Barenghi eta.1. (1990) and Lodge etal. (1993) independently have demonstrated the facile, multicomponent analysis of a wide range of PUFA-derived peroxidation products (e.g. conjugated dienes, epoxides and oxysterols) in samples of oxidized LDL by high-field H-NMR spectroscopy. Figure 1.9 shows the applications of this technique to the detection of cholesterol oxidation products (7-ketocholesterol and the 5a, 6a and 5/3,60-epoxides) in isolated samples of plasma LDL pretreated with added coppcr(Il) or an admixture of this metal ion with H2O2, an experiment conducted in the authors laboratories. 

Figure 7.32 shows the identification of an oxidation product of Irganox 1330 by means of APCI-MS. LC-APCI-MS/MS (high-resolution sector field-ion trap hybrid) has also been used for the analysis (elemental composition and structure) of Irganox PS 802 [636]. 

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