Indigo carmine, oxidation

Several methods using colorimetric estimation of peroxides have been used for LOX assays, but none are generally suitable. The thiocyanate method (Koch et al., 1958) is very sensitive but nonstoichiometric (Axelrod, 1974). Iodide oxidation, much used for peroxide determinations on fats and oils, is not suitable for enzyme assays, but it has been used in spot tests for column fractions (Wallace, 1972) and for enzyme localization in disc gel electrophoresis (Guss et al., 1%7), although several laboratories have experienced poor results with the latter. deLumen and Kazeniac (1976) have reported that dimethoxybenzidine is better than potassium iodide or thiocyanate for gel staining. Drapron and Nicholas (1977) have proposed the use of indigo carmine oxidation as a simple method for LOX determination. 

In order to explain the results shown in Fig. 2., the solution pH as a function of time was measured by a pH meter, and the results are displayed in Fig. 3. As can be seen from the data in the figure, when the initial solution pH is over 3.0, as reaction time increases, the solution pH decreases very fast to around 3.5 within 10 minutes, then reaches a lowest value of around 3.2 at 60 minutes, followed by a slight increase. What causes this interesting phenomenon We believed that the rapid decrease in solution pH is due to the fact that acidic intermediates are formed during the mineralization of 0.2 mM Indigo Carmine. Because of its complicated molecular structure, theoretically, it caimot be oxidized completely into CO2 and H2O in one step. 

Photoreactions on ZnO powder in aqueous suspension and in contact with gases have often been studied during the last few decades, and only a few aspects of this work are reviewed here. For example, nitrous oxide and methyl iodide were found to decompose when brought into contact at 20 °C with the illuminated surface of ZnO and nitrate, indigo carmine and p-nitrosodimethylaniline were found to be reduced in aqueous suspensions ZnO is of special interest as it is one of the standard electrode materials in conventional semiconductor electrochemistry and photo-electrochemistry Colloidal ZnO has not been available until recently. It... 

Fig. 3.12 The dependence on pH of the oxidation-reduction potential for c0x = cRcd (1) 6-dibromphenol indophenol, (2) Lauth s violet, (3) methylene blue, (4) ferricytochrome c/ferrocytochrome c, (5) indigo-carmine... 

The great oxidation power of electro-Fenton with BDD has also been confirmed in the comparative treatment of acidic aqueous solutions containing up to 0.9 g dm-3 of the dye Indigo Carmine by electro-Fenton and photoelectro-Fenton using BDD/02 and Pt/02 cells (Flox et al. 2006). The application of both methods... 

Beta-carotene indigo carmine iron oxides sunset yellow FCF tartrazine titanium dioxide. 

The use of an external indicator is somewhat tedious, but the titration can be simplified by using indigo carmine. This substance is readily decolorized by the available chlorine. A measured volume of arsenious oxide solution such as 25 ml, together with a little hydrochloric acid, are placed in a titration flask and a few drops of indigo carmine solution are added. The hypochlorite is then run in from a burette until the blue colour changes to a yellowish tinge. 

Kinetic spectrophotometric determination methods for Ag(I) were proposed, based on the strong catalytic effect of this ion on the controlled oxidation of various dyes, by measuring the rate of change of absorbance. Some recently published examples are Ag(I)-catalyzed peroxodisulfate oxidation of brilliant cresyl blue (33)104 or gallocyanine (34)105, both in the presence of 1,10-phenanthroline (35) and hexacyanoferrate (36) oxidation of indigo carmine (37)106. 

To cause these changes, take the yellow solution and slowly pour it from one beaker into another (thus allowing oxygen from the air to dissolve in). The solution will turn red, and then green and then back to yellow. These changes in color are the result of reversible oxidation and reduction reactions that indigo carmine undergoes under the experimental conditions. 

The use of the Pt/GDE system with UVA irradiation, i.e., the PEF process, is illustrated in Fig. 2 for the treatment of clofibric acid with 1.0 mM Fe ". The much quicker TOC abatement with > 90 % mineralization at 360 min is due to the contribution of reactions (10) and (11). The photolysis of Fe(III)-oxalate by-products that are quite refractory to the OH-mediated oxidation is the crucial, distinctive event. For some pollutants, the efficiency of the PEF process can be further enhanced by using a metal ion cocatalyst. The action of Co ", Mn ", and Ag", among others, has been surveyed, but the most interesting effect has been demonstrated for the Cu VCu" couple. In the case of indigo carmine dye shown in Fig. 2, for example, the positive synergistic effect of Fe " and Cu " that promotes the quicker mineralization is accounted for by the easier oxidation of some nitrogenated complexes of Cu(II) (e.g., with oxamate) compared with the competitively formed Fe(III) complexes, which are more slowly removed by OH and can only be photodegraded. In this system, Cu" can be... 

Diamino-diphenylene oxide Catalytic acceleration of the oxidation of indigo carmine with 0.003 193... 

Riffault et al. (1874) describe this pigment as s3monymous with indigo carmine (q.v.). There is however, a further contradictory reference to this in Riffault et al. as synonymous with smalt (. v.), Saxony being where this colour is prepared the best . Tingry (1804) also considers this to be vitreous oxide of cobalt or smalt. See also Saxon blue. 

The oxidation of indigo carmine by H20a is catalysed by the metal ions ... 

---