Thermodynamic studies on mixed micellization of amphiphilic drug amitriptyline hydrochloride and nonionic surfactant Triton X-100

In the present work, we report the surface properties and mixed micellization of a tricyclic antidepressant drug amitriptyline hydrochloride (AMT) with nonionic surfactant poly(ethylene glycol) t-octylphenyl ether (TX-100) using surface tension measurements. The surface properties in aqueous solution of AMT drug in the absence and presence of TX-100 are presented. The critical micelle concentration (cmc), maximum surface excess concentration at the air/water interface (Gamma(max)) and the minimum area per surfactant molecule at the air/water interface (A(min)) parameters are evaluated. Gamma(max) increases and cmc as well as A(min) decrease with increasing concentration (mole fraction) of the additive (TX-100). We also report the thermodynamics of AMT in the absence and presence of TX-100 and evaluated Gibbs energies (viz., at air/water interface (G(min)((s))), the standard Gibbs energy change of micellization (Delta(mic)G(0)), the standard Gibbs energy change of adsorption (Delta(ads)G(0)), the excess free energy change of micellization (Delta G(ex)(m))). (C) 2012 Elsevier B.V. All rights reserved.