Acido-basic properties of lipophilic substances: A surface potential approach

A general procedure allowing the acido-basic properties of lipophilic compounds to be defined is described. Drugs are spread at the air-water interface and the surface potential is recorded at different pH values of the aqueous subphase. Comparison of this experimental parameter and the Gouy-Chapman theory prediction allows the calculation of the acid (or basic) dissociation constants and the surface charge density.