Calorimetry studies of chlorpromazine hydrochloride in solution

Yoshihito David Saito, Shandiz Tehrani, Manko M. Okamoto, Henry H. Chang, Phoebe Dea

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Abstract

The self-association of the tranquilizer chlorpromazine hydrochloride in aqueous solution was studied. Using isothermal titration calorimetry, the critical micelle concentration and solvent-micelle interactions were evaluated as a function of temperature, ionic strength, and pH. The enthalpy of demicellization, ΔHdemic, was directly measured from the experimental enthalpy values, which showed that the spontaneous demicellization of chlorpromazine hydrochloride is a highly endothermic process under all experimental conditions studied. The thermodynamic parameters were subsequently calculated from the temperature dependent thermograms. At 25 °C, the critical micelle concentration was determined to be 3.2 mM at pH 6.5 with a ΔHdemic of 12.5 kJ/mol, a ΔGdemic of 24.3 kJ/mol, and a TΔSdemic of -10.1 kJ/mol. Our results suggest that the enthalpy-entropy compensation theory may be applied to these micelles. In addition, using differential scanning calorimetry, a broad endothermic demicellization peak was observed in postmicelle solutions during heating scans at approximately 45 °C. Cooling scans revealed a very broad peak centered around 40 °C that corresponds to the heat of micellization.

Original languageEnglish (US)
Pages (from-to)6391-6395
Number of pages5
JournalLangmuir
Volume16
Issue number16
DOIs
Publication statusPublished - Aug 8 2000
Externally publishedYes

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ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry

Cite this

Saito, Y. D., Tehrani, S., Okamoto, M. M., Chang, H. H., & Dea, P. (2000). Calorimetry studies of chlorpromazine hydrochloride in solution. Langmuir, 16(16), 6391-6395. https://doi.org/10.1021/la991297l