Chemical Engineering Communications, Vol.199, No.4, 461-471, 2012
Study of Clouding and Dye Solubilization in Clomipramine Hydrochloride-Electrolyte Systems
Clomipramine hydrochloride (CLP), an antidepressant drug, is amphiphilic in nature and self-aggregates at 22mM (25 degrees C). The drug shows a critical demixing (liquid-liquid phase separation) when the temperature is raised. The critical point (CP; often referred to as the cloud point) is susceptible to the presence of additives. Herein, we report the clouding phenomenon occurring in CLP drug solutions in the presence of electrolytes. At a fixed drug concentration (50 mM) and fixed pH (6.25), CLP shows CP at 32 degrees C, which can be tuned with the addition of salts. With NaX (X=F-, Cl-, Br-) and MBr (M = Li+, Na+, K+) salts, the CP increases due to adsorption and salting-in/salting-out phenomenon. Quaternary salts, tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), and tetrabutylammonium bromide (TBAB) form mixed micelles and hence increase CP of the drug solution. Dye solubilization experiments on drug-electrolyte systems and energetic parameters evaluated for drug-NaF system also support the explanations forwarded for the process of clouding.