Abstract
Herein, we have investigated the interaction between a phenothiazine drug promethazine hydrochloride (PMT) and nonionic surfactant t-octylphenoxypolyethoxyethanol (TX-100) in aqueous solutions using a conductometric technique at different temperatures and compositions. The evaluated critical micelle concentration (cmc) values are lower than cmc(id) values suggesting attractive interactions of mixed micelles components. It is observed that with the increase in temperature, the cmc value increases first and after the value decreases at higher temperature. At 298.15 K, the maximum cmc values were attained in presence or absence of TX-100. The bulk properties of solution were studied by means of different theoretical models reported in the literature such as Clint, Rubingh, Motomura, and Rodenas for explanation and comparison of results of different binary mixtures of the drug and TX-100. The negative values of interaction parameter (beta) obtained from the regular solution theory (RST) recommend synergistic interactions. Activity coefficients (f(1) and f(2)) calculated by all theoretical models used herein were obtained to be always below unity indicating nonideality in all binary mixtures. Thermodynamic parameters (like standard Gibbs energy (Delta Gm degrees), enthalpy (Delta H-m degrees), and entropy (Delta S-m degrees)) are also evaluated which propose dehydration of hydrophobic portion of the drug at higher temperatures. The above results obtained may be helpful in model drug delivery systems.