The organic solvent-water partition coefficient (LogD or LogP) is measured using the shake flask methodology. The aqueous phase used is a 10mM solution of sodium phosphate buffer adjusted to pH 7.4. Octanol is typically used as the organic solvent, but this may be substituted with the desired choice of alternative organic solvent that best models the environment in which the test compound is intended to be applied.
The lipophilicity of n-octanol is considered to resemble lipid-bilayer membranes, and distribution of chemicals between n-Octanol and the aqueous phase simulates their ability to passively diffuse across biological membranes.
