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

Abstract

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 (Γmax) and the minimum area per surfactant molecule at the air/water interface (Amin) parameters are evaluated. Γmax increases and cmc as well as Amin 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 (Gmin(s)), the standard Gibbs energy change of micellization (ΔmicG0), the standard Gibbs energy change of adsorption (ΔadsG0), the excess free energy change of micellization (ΔGexm)).