Effect of anionic surfactant and temperature on micellization behavior of promethazine hydrochloride drug in absence and presence of urea

The interaction between promethazine hydrochloride (PMH) drug and sodium dodecyl sulfate (NaDS) have been carried out conductometrically at various temperatures and concentration to examine the monomeric as well as micellar phases of aqueous solutions of mixed systems in absence and attendance of urea (NH2CONH2). PMH is belonged to the group of drugs called phenothiazines and is employed to care for allergy symptoms. Urea increases the cmc value because of enhancement in the surface charge of the micelles/mixed micelles. Relevant parameters were evaluated using the various theoretical models for binary mixed systems. The values of micellar mole fraction (X1m) and the ideal micellar mole fraction (X1id) were found to higher than the corresponding mole fraction (α1) of surfactant. The micellar interaction parameters (β), were determined from the critical micelle concentration (cmc) values using the approach of Rubingh's regular solution theory. Clint's model was also used to explain the nonideal behavior of the systems. In presence of urea the interaction between the studied components decreases. The evaluated excess free energy (ΔGexRub) explains the more stability of mixed micelles in comparison to micelles of the pure component; the stability decreases in attendance of urea. Also, activity coefficients (f1 and f2) are always less than unity suggesting non-ideality in the mixed solution. The ΔG0m for all studied systems were found out to be negative i.e., micellization processes are energetically favourable.