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Osmium assay in fixatives and stained rat tissues by means of acid and o,o′-dihydroxo substituted monoazo dyes and some flavonoids

100%
Rydchuk M., Mykhalyna G., Dobryanska O., Korkuna O., Vrublevska T.
Open Chemistry
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2011
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vol. 9
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issue 5
886-895
EN
New simple, rapid and accurate spectrophotometric techniques for osmium assays in fixatives and stained tissues have been elaborated using acid (Tropaeolin O, Tropaeolin OOO-I, Tropaeolin OOO-II, Orange G), o,o′-dihydroxo substituted azo dyes (Eriochrome Blue Black R, Acid Chrome Dark-Blue, Eriochrome Black T) and flavonoids (morin, quercetin, luteolin). Methods are based on sensitive osmium(IV) reactions with reagents and the formation of stable coloured compounds. Tolerance ratios of main matrix components of histological specimens during Os(IV) spectrophotometric determination with reagents has been established. Results of osmium determination in fixatives and fixed tissues, obtained by means of different reagents, appeared to be sufficiently similar, although effects of matrix components differ. The accuracy of spectrophotometric osmium assay in fixatives with azo dyes has been confirmed with voltammetric investigations. Results obtained from osmium uptake by rat gum tissues are valuable for clinical testing of dental drugs, indicating the influence of drug treatment on the gums. [...]
2
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Spectrophotometric determination of aqueous acidity constants of three azo dyes

88%
Alizadeh K., Rezaei B., Maddah B.
Open Chemistry
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2010
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vol. 8
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issue 2
392-395
EN
The two successive steps acidity constants of three azo dye derivatives D1–D3, were determined by a spectrophotometric method using 0.10 M KNO3 as supporting electrolyte in water solvent. The electronic spectra of the compounds were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants can be solved very satisfactorily from absorbance data, by combining the data obtained in the spectrometric determinations with graphic methods as the absorbance diagrams. An A-diagram shows the relative absorbance changes at two wavelengths as a function of the pH. For a one-step system, the absorbance at any wavelength must be proportional to the absorbance at any other wavelength, so an A-diagram for all wavelength combinations for such a system must be linear (rank, s=1). However, if a system is governed by two or more equilibria, the A-diagrams corresponding to multi-step titrations will change direction every time a new equilibrium becomes dominant in the system. Analysis of the each uniform sub-region can then be used in evaluating of the corresponding equilibrium. A-diagrams for all wavelength combinations suggest that these systems have the rank two(s=2). The results revealed that the Ka(1) and Ka(2) values of different azo dyes follow the order D3>D2>D1. [...]
3
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Characterization and photocatalytic activity of Ti/TinOm∙ ZrxOycoatings for azo-dye degradation

88%
Sakhnenko N., Ved M., Bykanova V., Nikiforow K.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
Anodic oxidation of VT1-0 titanium and E-125 zirconium alloy in aqueous electrolyte solutions based on H2SO4 and K4P2O7 was used to obtain oxide coatings composed of Zr/ZrO2, Ti/TiO2, and mixed oxide systems Ti/TinOm ∙ ZrxOy. It was shown that, depending on the electrolyte рН, the films contained from 0.17 to 2.1% wt. of zirconium. The catalytic activity of the synthesized coatings in the oxidation reaction of the methyl orange azo dye under UV irradiation was established. The process rate constants and synergy factors for the mixed systems were calculated.
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