Phenol oxidation test

As mentioned earlier, physiological concentrations of carotenoids in vivo are in the micromolar range, mainly because of limited bioavailabiUty. Also, the antioxidant efficiencies of carotenoids after absorption are probably limited. Concentrations before absorption are much higher and can justify possible antioxidant actions in vivo. To test this hypothesis, Vulcain et al. developed an in vitro system of lipid peroxidation in which the oxidative stress is of dietary origin (metmyoglobin from meat) and different types of antioxidants (carotenoids, phenols) are tested. 

A widespread method for determining the induction period for autoxidation of oils and fats consists of passing a continuous stream of air through the heated sample and collecting the volatile acids evolved in a water trap, where they are determined on a real time basis. The time plot usually presents a flat appearance for a certain period and then takes off in an accelerated manner. This test is the basis of several national and international standards (e.g. AOCS Cd 12b-92—oil stability index" ISO 6886—accelerated oxidation test for oxidative stability of fats and oils ) and the design of the Rancimat equipment, where the end determination is based on conductivity measurements . In addition to oxidation stability as determined by the Rancimat method and POV, which negatively affects virgin olive oil stability, other nonstandard properties were proposed for better assessment of the quality of this oil, namely LC determination of Vitamin E (21), colorimetric determination of total polar phenols and UVD of total chlorophyll. ... 

Tea extracts and tea polyphenols inhibit copper- and peroxide-induced oxidation of LDL in vitro (116,123,124). The inhibitory concentration for 50% reduction (IC50) values for inhibition of copper-induced oxidation of LDL by some phenolic antioxidants are listed in Table 7. The IC q for epigallocatechin gallate was found to be 0.075 [imM, which was the most potent of all the phenolic antioxidants tested (123,124). Similar results have been reported elsewhere (115,116,125,126). 

In order to study the Fe-assisted FC mineralization of phenol, experiments were typically performed for the FC oxidation of phenol to determine the optimum pH at which the rate of oxidation was the highest possible in the reactor setup employed for this study. Then a series of tests were carried out to identify the aromatic and carboxylic intermediates of phenol oxidation at the optimum pH value. Subsequently, more tests with those aromatics identified as phenol oxidation intermediates were performed to unveil the intermediates produced during their corresponding FC oxidations and also to compare with the Fe-assisted FC reactions. 

Total Phenolics by Folin Ciocalteau. The Folin-Ciocalteau total phenol level decreased with all fining agents and significantly with carbon and bentonite at all levels and PVPP at the highest level (Table III). One interference in the Folin-Ciocalteau assay is protein (29). This is of specific importance in this study because the vsdnes are diluted to equivalent total phenol levels according to this assay for the subsequent LDL oxidation tests. New finished wines have very low levels of protein, however, the concentration of proteins that remain after fining has not been well documented. 

Color reactions Boric acid (hydroxyquinones). Dimethylaminobenzaldehyde (pyrroles). Ferric chloride (enols, phenols). Haloform test. Phenylhydrazine (Porter-Silber reaction). Sulfoacetic acid (Liebermann-Burchard test). Tetranitromethane (unsaturation). Condensation catalysts /3-Alanine. Ammonium acetate (formate). Ammonium nitrate. Benzyltrimethylammonium chloride. Boric acid. Boron trilluoride. Calcium hydride. Cesium fluoride. Glycine. Ion-exchange resins. Lead oxide. Lithium amide. Mercuric cyanide. 3-Methyl-l-ethyl-2-phosphoiene-l-oxlde. 3-Methyl-1-phenyi-3-phoipholene-1-oxide. Oxalic acid. Perchloric acid. Piperidine. Potaiaium r-butoxIde. Potassium fluoride. Potassium... 

Not only can molecular design improve the miscibility with other oils, it can also confer ILs with special functions, such as antioxidation and the ability to adapt to a broader temperature range. We synthesized three imidazolium-based ILs containing sterically hindered phenol groups with antioxidant functions and evaluated the tribological behaviors of these ILs as additives for PEG appfication in steeFsteel contacts on an Optimol SRV-IV oscillating reciprocating friction and wear tester, as well as on MRS-IJ four-ball testers [100]. The rotary bomb oxidation test (RBOT) test, thermal analysis, and Cu strip test results revealed that synthesized ILs possessed excellent antioxidation capability. 

The activity tests of catalysts for liquid-phase phenol oxidation were carried out at operating conditions for which both heat and mass transfer resistances were negligible. Residual phenol concentration as a function of time for some typical oxidation runs is illustrated in Figure 1. 

Finally, the chemical stability of the catalysts employed in this study was tested by means of XRD and EDXS analyses. The examination of fresh and used catalysts shows that during the reaction course metal ions are slowly leached into the aqueous solution, which can be attributed either to the temperature of operation or the presence of complexing carboxylic acids and benzoquinones in the liquid-phase. Contrary to the results obtained in continuous-flow fixed-bed reactors [8, 9], the extent of catalyst dissolution in the slurry reactor was considerable. This is probably due to the higher accumulation of benzoquinones which are known to form stable complexes with metal ions. Examination of the X-ray powder diffraction patterns of the molecular sieves before and after the liquid-phase phenol oxidation... 

Phenol concentration in the aqueous phase versus time in the photocatalytic oxidation tests performed in the PMC at pH 3.1 and 5.5 (Molinari R. eta/., unpublished data). 

The autoxidation of trilinolein was more complicated than that of the simple fatty esters and did not follow the same rate equation. The order of the reaction was about 0.84 compared to 1.0 for the simple fatty esters. The efficiency of the initiators used, DMVN, was increased to 100% in the trilinolein compared to about 75% in the simple fatty esters. The difference in kinetic behavior between trilinolein and methyl linoleate was attributed to the tendency of the triacylglycerol to form aggregates. The kinetic induction period approach used to measure oxidizability may be subject to errors because of the changes in efficiency of some of the artificial initiators used according to the system and the lipid substrate. Phenolic antioxidants such as a-tocopherol are also affected by the colloidal properties of the lipids used in the oxidation test system employed (Chapter 9). 

Phenol is commonly employed as a reference molecule for aqueous oxidation tests of heterogeneous catalysts in order to gain knowledge about its performance for abatement of aromatic compounds. Phenol CWO over our catalysts yields hydroquinone, benzo-quinone, cathecol, acetic acid, formic acid, oxalic acid, fumaric acid, maleic acid, maloiuc acid and carbon dioxide, but with different distribution. 

Colorimetric Methods. Numerous colorimetric methods exist for the quantitative determination of carbohydrates as a group (8). Among the most popular of these is the phenol—sulfuric acid method of Dubois (9), which rehes on the color formed when a carbohydrate reacts with phenol in the presence of hot sulfuric acid. The test is sensitive for virtually all classes of carbohydrates. Colorimetric methods are usually employed when a very small concentration of carbohydrate is present, and are often used in clinical situations. The Somogyi method, of which there are many variations, rehes on the reduction of cupric sulfate to cuprous oxide and is appHcable to reducing sugars. 

Property ASTM Test Phenolics Foamedin Syntactic Place Castable Polyvinyl Chloride Rigid Closed Cell Phenylene Oxide Foamable Resin Polycarbonate Polystyrene Medium-Density Foam Polystyrene Molded Extruded Polyurethane Rigid Closed Cell... 

Attempts have been made to exploit the intrinsic C2 symmetry of the phenolate-based dinickel core in enantioselective catalytic reactions. Therefore, enantiomerically pure C2-symmetric ligands such as (736a) and the corresponding dinickel systems (736b) have been prepared ( Equation (27)),1890 and (736b) was tested in the epoxidation of unfunctionalized alkenes with sodium hypochlorite as the oxidant. The catalytic reaction was found to be highly pH dependent with an optimum at a pH of 9. While the complex is catalytically active, significant enantioselectivity was not achieved. 

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