V. Borek

The use of redox reactions in the analysis of dyes and dye intermediates: XIV. Direct current polarography of 4,4′-disubstituted azobenzenes in acetonitrile

Abstract The polarographic reduction of some 4,4′-disubstituted azobenzenes in an acetonitrile medium was studied. The diffusion character of the observed limiting currents was confirmed and a mechansim of polarographic reduction proposed. The possibility of analytical application is briefly discussed.

The use of redox reactions in the analysis of dyes and dye intermediates: XV. Direct current polarography of some water-insoluble azo pigments in acetonitrile

Abstract The polarographic behavior of five water-insoluble azo pigments was studied in an acetonitrile medium. The diffusion character of the observed limiting currents was confirmed and a mechanism was proposed for the polarographic reduction. The possibility of an analytical application is briefly discussed.

The analysis of dyes and dye intermediates by physico-chemical methods: I. Thin-layer chromatographic and spectrophotometric behavior of some azobenzene derivatives

Abstract Thin-layer Chromatographic behavior of 14 azobenzene derivatives was studied, suitable eluents were found, and the R f values were determined. Spectrophotometric behavior of these substances in acetonitrile was studied, as well as the influence of acids and bases on the studied spectra. The validity of the Lambert—Beer law in a concentration region from 1 × 10 −5 to 7 × 10 −5 was verified.

The use of redox reactions in the analysis of dyes and dye intermediates: XVI. The influence of proton donors on direct current polarographic behavior of 4,4′-disubstituted azobenzenes in acetonitrile☆

Abstract The influence of water and perchloric acid on the polarographic behavior of 4,4′-disubstituted azobenzene derivatives in acetonitrile has been investigated. The conditions were defined for the polarographic determination of the test substances in acetonitrile containing various concentration of water. The presence of strong acids prevents analytical use of these reactions.

The use of redox reactions in the analysis of dyes and dye intermediates: XI. A chromometric determination of some azobenzene derivatives in an acetonitrile-methanol-water mixed medium☆

Abstract Optimal conditions for a direct and indirect determination of 14 azobenzene derivatives with chromium(II) chloride have been found.

The use of redox reactions in analysis of dyes and dye intermediates: X. Polarographic and constant-potential coulometric determination of 4,4′-dihydroxyazobenzene and 4-nitro-4′-hydroxyazobenzene☆

Abstract Conditions have been found for a polarographic and constant-potential coulometric determination of 4.4′-dihydroxyazobenzene and 4-nitro-4′-hydroxyazobenzene in buffered media.

The use of redox reactions in the analysis of dyes and dye intermediates: XVIII. Determination of 4,4′-disubstituted azobenzenes in acetonitrile using TAST and DP polarography☆

Abstract The TAST and DP polarographic behavior of 4,4′-disubstituted azobenzenes in acetonitrile in the presence of tris-(hydroxymethyl)-aminomethane was investigated. It has been found that this substance decreases the adverse effect of water and proton donors by functioning as a buffer. The use of DPP enables an improvement in the sensitivity of the polarographic determination of the test substances.

The analysis of dyes and dye intermediates by physicochemical methods: II. Thin-layer chromatographic and spectrophotometric behavior of some water-insoluble azo-pigments

Abstract Thin-layer chromatographic behavior of 5 azo-pigments was studied, suitable eluants were found, and the R f values were determined. Spectrophotometric behavior of these substances in acetonitrile was studied, as well as the influence of acids and bases on the studied spectra. The validity of the Lambert-Beer law in a concentration region from 1 × 10 −5 to 7 × 10 −5 M was verified.

The use of redox reactions in the analysis of dyes and dye intermediates: XVII. The influence of proton donors on direct current polarographic behavior of some water-insoluble azo pigments in acetonitrile

Abstract The influence of water and perchloric acid on the polarographic behavior of some water-insoluble azo pigments in acetonitrile has been investigated. The conditions were defined for the polarographic determination of the test substances in a mixed acetonitrile-water medium. The presence of strong acids prevents analytical use of these reactions.

The use of redox reactions in the analysis of dyes and dye intermediates: XIII. A titanometric determination of azo pigments

Abstract The test azo pigments (I–V) were determined reductometrically with a standard solution of trivalent titanium, in a buffered solution containing citrate ions.