Published: Journal of Chromatographic Science, Volume
37, Number 9, October 1999, pp. 375-382
Development and Validation of a Procedure for Estimating
the Hydrophobicity of Structurally Unrelated Compounds by Micellar Liquid Chromatography
I. Beleña-Pozo, R.M. Villanueva-Camañas,
S. Sagrado, and M.J. Medina-Hernández
Reversed-phase liquid chromatography has been used most often
to estimate values of log P, but despite years of study, there is no universally
accepted method of performing these estimations. The main problem has to do with
the fact that the hydrophobic parameter, log kw, depends on the hydrogen bond
acceptor–donor character of the compounds. The use of micellar mobile phases
to perform these estimations is evaluated here, and the influence of the nature
of the surfactant (anionic, cationic, and nonionic) on the log k–log P relationships
is studied. The use of a nonionic surfactant, such as Brij35, to prepare the mobile
phases provided adequate results regardeless of the hydrogen bond acceptor–donor
character of the compounds, whereas noncongener behaviors are found with anionic
and cationic surfactants. This enabled the establishment of a calibration set
consisting of 7 compounds with variable hydrophobicity in order to calibrate new
columns and predict log P values. In these conditions, the hydrophobicity of structurally
unrelated compounds in the –0.1 < log P < 4.5 range can be measured.
To evaluate the accuracy of predictions, the hydrophobicity of 27 compounds is
determined and compared with the log P values calculated using the ACD–log
P program. Nonsignificant differences between the predicted and the theoretical
log P values were achieved at 95% probability level.
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