The Effects of pH on Chlorpromazine Hydrochloride Solution. Wen Lee & Jodie Matz

Abstract

Chlorpromazine hydrochloride (CPZ) is an amphiphilic compound that forms micellar aggregates in aqueous solution. This nanostructure minimizes the total energy of the system because the amphiphiles orient themselves to reduce hydrocarbon-water repulsion. The process of micellization/demicellization is a dynamic one, with micelles changing size and monomers going from bulk solution to different aggregates continuously. The effects of pH and concentration on the formation and breakdown of micelles were studied using differential scanning calorimetry at a temperature range of 20-60 ?C. We observed an enthalpy of demicellization of 11 kJ/mole and a peak temperature of 37.9?C for a 10mM CPZ sample at pH 6.5. An increase in the enthalpy of demicellization and a decrease in peak temperature were observed when the pH was changed from 6.0 to 6.5. Enthalpy values and peak temperatures were also obtained for CPZ concentrations of 10, 20, and 30 mM. It was found that with increasing concentration, peak temperatures increase and enthalpy values decrease. The peaks observed in the thermograms for micellization were quite broad compared to those for demicellization.