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Anal Bioanal Chem. 2004 Oct;380(4):664-8. Epub 2004 Sep 24.

Determination of acidity constants of enolisable compounds by capillary electrophoresis.

Author information

1
Laboratoire d'Analyse des Systèmes Organiques Complexes, UPRES EA 2659(SMS) IRCOF et IFRMP, Université de Rouen, 55 rue Saint Germain, 27000 Evreux, France.

Abstract

Research on the structure-activity relationships of molecules with acidic carbon atoms led us to undertake a feasibility study on the determination of their acidity constants by capillary electrophoresis (CE). The studied molecules had diverse structures and were tetronic acid, acetylacetone, diethylmalonate, Meldrum's acid, 3-methylrhodanine, nitroacetic acid ethyl ester, pyrimidine-2,4,6-trione, 3-oxo-3-phenylpropionic acid ethyl ester, 1-phenylbutan-1,3-dione, 5,5-dimethylcyclohexan-1,3-dione and homophthalic anhydride. The p Ka range explored by CE was therefore very large (from 3 to 12) and p Ka values near 12 were evaluated by mathematical extrapolations. The analyses were carried out in CZE mode using a fused silica capillary grafted (or not) with hexadimethrine. Owing to the electrophoretic behaviour of these compounds according to the pH, their acidity constants could be evaluated and appeared in perfect agreement with the literature data obtained, a few decades ago, by means of potentiometry, spectrometry or conductimetry. The p Ka of homophthalic anhydride and 3-methylrhodanine were evaluated for the first time.

PMID:
15448970
DOI:
10.1007/s00216-004-2784-x

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