Retention of bile salts in micellar electrokinetic chromatography: relation of capacity factor to octanol–water partition coefficient and critical micellar concentration

The capacity factors of 16 anionic cholates (from six bile salts, including their glyco- and tauro-conjugates) were determined in a micellar electrokinetic chromatography (MEKC) system consisting of buffer, pH 7.5 (phosphate–boric acid; 20 mmol/l) with 50 mmol/l sodium dodecyl sulfate (SDS) as micel...

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Bibliographic Details
Published in:Journal of chromatography. B, Biomedical sciences and applications Biomedical sciences and applications, 2001-12, Vol.765 (2), p.113-120
Main Authors: Lucangioli, Silvia E, Carducci, Clyde N, Tripodi, Valeria P, Kenndler, Ernst
Format: Article
Language:English
Subjects:
Analysis
Bile Acids and Salts - chemistry
Bile salts
Biological and medical sciences
Cholates
Chromatography, Micellar Electrokinetic Capillary - methods
General pharmacology
Medical sciences
Micelles
Octanols - chemistry
Pharmacology. Drug treatments
Water - chemistry
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Summary:The capacity factors of 16 anionic cholates (from six bile salts, including their glyco- and tauro-conjugates) were determined in a micellar electrokinetic chromatography (MEKC) system consisting of buffer, pH 7.5 (phosphate–boric acid; 20 mmol/l) with 50 mmol/l sodium dodecyl sulfate (SDS) as micelle former and 10% acetonitrile as organic modifier. The capacity factors of the fully dissociated, negatively charged analytes (ranging between 0.2 and 60) were calculated from their mobilities, with a reference background electrolyte (BGE) without SDS representing “free” solution. For comparison, the capacity factors were derived for a second reference BGE where the SDS concentration (5 mmol/l) is close to the critical micellar concentration (CMC). The capacity factors are compared with the logarithm of the octanol–water partition coefficient, log P OW, as measure for lipophilicity. Clear disagreement between these two parameters is found especially for epimeric cholates with the hydroxy group in position 7. In contrast, fair relation between the capacity factor of the analytes and their CMC is observed both depending strongly on the orientation of the OH groups, and tauro-conjugation as well. In this respect the retention behaviour of the bile salts in MEKC seems to reflect their role as detergents in living systems, and might serve as model parameter beyond lipophilicity.
ISSN:0378-4347
1387-2273
DOI:10.1016/S0378-4347(01)00417-0