Oxidation pathways of natural dye hematoxylin in aqueous solution

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Title:Oxidation pathways of natural dye hematoxylin in aqueous solution
Creators:
Sokolová, Romana
Degano, Ilaria
Hromadová, Magdaléna
Bulíčková, Jana
Gál, Miroslav
Valášek, Michal
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 75, 11, pp. 1097-1114
Uncontrolled Keywords:Oxidation, Dye degradation, Cyclic voltammetry, Hematoxylin

Abstract

The oxidation mechanism of hematoxylin was studied in phosphate buffers and 0.1 M KCl by cyclic voltammetry and UV-Vis spectroscopy under deaerated conditions. The redox potential of hematoxylin in buffered solution strongly depends on pH. A two electron oxidation is preceded by deprotonation. The homogeneous rate of deprotonation process of hematoxylin in 0.1 M phosphate buffer is <i>k</i><sub>d</sub> = (2.5 ± 0.1) × 10<sup>4</sup> s<sup>–1</sup>. The cyclic voltammetry under unbuffered conditions shows the distribution of various dissociation forms of hematoxylin. The dissociation constants p<i>K</i><sub>1</sub> = 4.7 ± 0.2 and p<i>K</i><sub>2</sub> = 9.6 ± 0.1 were determined using UV-Vis spectroscopy. The final oxidation product was identified by gas chromatography with mass spectrometry detection as hemathein. The distribution of oxidation products differs under buffered and unbuffered conditions. The dye degradation in natural unbuffered environment yields hemathein and hydroxyhematoxylin, which is absent in buffered solution.

Title:Oxidation pathways of natural dye hematoxylin in aqueous solution
Creators:
Sokolová, Romana
Degano, Ilaria
Hromadová, Magdaléna
Bulíčková, Jana
Gál, Miroslav
Valášek, Michal
Uncontrolled Keywords:Oxidation, Dye degradation, Cyclic voltammetry, Hematoxylin
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:75
Number:11
Page Range:pp. 1097-1114
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc2010096UNSPECIFIED
ID Code:6265
Item Type:Article
Deposited On:12 Nov 2010 12:04
Last Modified:12 Nov 2010 11:04

Citation

Sokolová, Romana; Degano, Ilaria; Hromadová, Magdaléna; Bulíčková, Jana; Gál, Miroslav; Valášek, Michal (2010) Oxidation pathways of natural dye hematoxylin in aqueous solution. Collection of Czechoslovak Chemical Communications, 75 (11). pp. 1097-1114.

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