Study of ionizable drugs transfer across the water/1,2-dichloroethane interface with phase volume ratio equal to unity using a three-electrode system

The electrochemical behavior of ionizable drugs (Amitriptyline, Diphenhydramine and Trihexyphene- dyl) at the water/1,2-dichloroethane interface with the phase volume ratio (r = Vo/Vw) equal to 1 are investigated by cyclic voltammetry. The system is composed of an aqueous droplet supported at an Ag/AgCl disk electrode and it was covered with an organic solution. In this manner, a conventional three-electrode potentiostat can be used to study the ioni-zable drugs transfer process at a liquid/liquid interface. Physicochemical parameters such as the formal transfer potential, the Gibbs energy of transfer and the standard par-tition coefficients of the ionized forms of these drugs can be evaluated from cyclic voltammograms obtained. The ob-tained results have been summarized in ionic partition dia-grams, which are a useful tool for predicting and interpret-ing the transfer mechanisms of ionizable drugs at the liq-uid/liquid interfaces and biological membranes.