Interaction between antidepressant drug and anionic surfactant in low concentration range in aqueous/salt/urea solution: A conductometric and fluorometric study

Aqueous/salt/urea micellar solutions of amphiphilic antidepressant drug amitriptyline hydrochloride (AMT) and anionic surfactant sodium dodecylbenzenesulfonate (SDBS) have been examined by conductivity and fluorescence measurements at different temperatures and composition. From the conductometric study, values of critical micelle concentration (cmc) of drug have been evaluated and analyzed in terms of effect of surfactant on the hydrophobic nature of AMT-SDBS complex. The values of critical micelle concentration (cmc) and other aggregation parameters, micellar mole fraction (X1) and interaction parameters (β) were obtained and discussed in detail. In mixtures of AMT and SDBS, the synergistic interactions in mixed micelles formation increases with the raise in mole fraction of surfactant in absence and attendance of salt/urea. Thermodynamic parameters of the mixtures in aqueous as well as in salt/urea solution have been evaluated by means of a pseudo-phase model. The effect of NaCl shows the salting-out effect, which promotes aggregate formation of AMT and SDBS as well as their mixed systems at lower concentration relative to aqueous solution. The micelle aggregation number (Nagg) of drug increases with the raise in surfactant mole fraction in mixtures. Nagg value of individual and mixed amphiphiles rises in the presence of electrolyte while reduces in the occurrence of urea.