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Updated: Aug 21, 2026

A New Straightforward Method for Lipophilicity (logP) Measurement using 19F NMR Spectroscopy
Published on: January 30, 2019
Estimation of the ethanol/water solubility profile from the octanol/water partition coefficient
Stephen G Machatha1, Samuel H Yalkowsky
1College of Pharmacy, The University of Arizona, 1703 E. Mabel Street, Rm# 441, Tucson, AZ 85721-0207, USA. machatha@pharmacy.arizona.edu
Abstract:
While the ethanol/water solubility profiles of very polar and very non-polar drugs are monotonic, many semi-polar drugs show a maximum solubility at an ethanol volume fraction (f(max)) between 0 and 1. A sigmoidal relationship was observed between the value of f(max) and the log of the octanol/water partition coefficient (logK(ow)) of the solute. This relationship reasonably predicts the value of the volume fraction of ethanol that gives maximum solubility (f(max)). Combining this sigmoidal relationship with the previously reported linear relationship between the logK(ow) and the initial slope of the plot of log solubility versus ethanol composition [Li, A., Yalkowsky, S.H., 1994. Solubility of organic solutes in ethanol/water mixtures. J. Pharm. Sci. 83, 1735-1740] enables the estimation of the total ethanol/water solubility profile.
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