Document Detail

Determination of the dissociation constants of sulfonated azo dyes by capillary zone electrophoresis and spectrophotometry methods.
MedLine Citation:
PMID:  11403485     Owner:  NLM     Status:  MEDLINE    
The dissociation constants of 10 sulfonated azo dyes, six of the most common food colours used as additives (Food Yellow 4, Food Yellow 3, Food Red 9, Food Red 7, Food Red 17 and Food Blue 5), and four commonly used as textile dyes (Acid Orange 7, Acid Orange 12, Acid Red 26 and Acid Red 88), have been determined by two different systems, one by using capillary electrophoresis (CE) with diode array detection and the other by using UV-visible absorption spectrophotometry, which has been used as reference method to obtain the pKa values. The pKa values obtained by CE were determined in two ways, first on the basis of the electrophoretic mobilities (calculated from the migration times), and after we propose a new methodology, in which the dissociation constants are determined from the spectra corresponding to the maxima of electrophoretic peaks. The pKa values obtained by using these CE methods have been compared with those obtained by using the spectrophotometric method. The results show that the pKa values obtained by the CE proposed method are in general closer to the reference values than those obtained from the electrophoretic mobilities. Moreover, the proposed method retains the advantages of CE, as the possibility of working with small amounts of sample, despite its purity.
M Pérez-Urquiza; J L Beltrán
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of chromatography. A     Volume:  917     ISSN:  0021-9673     ISO Abbreviation:  J Chromatogr A     Publication Date:  2001 May 
Date Detail:
Created Date:  2001-06-13     Completed Date:  2001-10-25     Revised Date:  2009-01-15    
Medline Journal Info:
Nlm Unique ID:  9318488     Medline TA:  J Chromatogr A     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  331-6     Citation Subset:  IM    
Department de Química Analítica, Universitat de Barcelona, Spain.
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MeSH Terms
Azo Compounds / chemistry*
Coloring Agents / chemistry*
Electrophoresis, Capillary / methods*
Hydrogen-Ion Concentration
Spectrophotometry, Ultraviolet / methods*
Reg. No./Substance:
0/Azo Compounds; 0/Coloring Agents

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