Surface, micellar, and thermodynamic properties of antidepressant drug nortriptyline hydrochloride with TX-114 in aqueous/urea solutions

This paper deals with a comprehensive study of the mixed micellization and adsorption behavior of mixed systems enclosing an amphiphilic antidepressant drug nortriptyline hydrochloride (NOT) and Triton X-114 (TX-114) (nonionic surfactant) in aqueous/urea (500 mmol·kg−1 and 1000 mmol·kg−1) solutions by tensiometric method. The NOT is used for the cure of depression. For comparison purpose cmc value of pure drug NOT was also evaluated by conductimetric technique. Different theoretical models like Clint, Rubingh, and Rosen were used to get information about the nature of interaction between the components in bulk and at the interface. Because of the occurrence of urea increase in the surface charge of the micelles was obtained resulting a delay of the micelles formation. The cmc values of the mixed systems of NOT and TX-114 were found to be in between the cmc values of pure components, which signify nonideal mixed system having attractive interactions in the absence and presence of urea. Various parameters such as micellar mole fractions of TX-114 (X1m, X1σ) in solution and at interface, interaction parameter (βm/βσ) in solution and at interface, and activity coefficient in solution and at interface were evaluated and discussed using Rubingh's and Rosen's models. Surface excess (Γmax) increases that means minimum area per head group (Amin) decreases as mole fraction (α1) of TX-114 increases in the absence/presence of urea. Different thermodynamic parameters have been calculated and discussed. The ∆G0m values achieved are all negative both in the absence and occurrence of urea.