Interaction of cationic amphiphilic drug nortriptyline hydrochloride with TX-100 in aqueous and urea solutions and the studies of physicochemical parameters of the mixed micelles

The interaction of amphiphilic antidepressant drug nortriptyline hydrochloride (NOT) with nonionic surfactant Triton X-100 (TX-100) was studied in this work using tensiometry in aqueous and in urea (500 mmol ∙ kg− 1 and 1000 mmol ∙ kg− 1) solutions at 303.15 K. Various models such as Clint, Rubingh, and Rosen etc. were employed to get the information regarding the nature of interaction between the compounds in bulk and at the interface. The CMC values of the mixed systems of NOT and TX-100 were found to be in between the CMC value of pure components, which suggest nonideal mixed system having attractive interactions in the absence and presence of urea. Enhancement in the surface charge of the micelles was obtained in the company of urea followed by halt of the micelles formation. Various physicochemical parameters, such as, micellar mole fraction (X1Rub) of TX-100, interaction parameters (βσ, βm) at monolayer air-water interface as well as in bulk solutions, thermodynamic parameters, activity coefficients (f1m, f2m), surface pressure at the CMC (πCMC), for the TX-100 and NOT in the mixed micelles were determined as discussed in detail. Thermodynamic parameters (minimum energy of surface (Gmin), standard Gibbs energy of adsorption (ΔGads∘), free energy of micellization (ΔG°m), excess Gibbs energy of the mixed monolayer (ΔGexσ), excess Gibbs energy of the micelle formation (ΔGexm) and free energy of micellization (ΔGMaeda0) (calculated by Maeda model)) and surface properties exposed that the addition of urea changes the relevant physicochemical properties which influence the process of micellization.