Solubility and stability of anhydrate/hydrate in solvent mixtures

Research output: Contribution to journalArticleScientificpeer-review

Researchers

Research units

  • Lappeenranta University of Technology

Abstract

In this paper, the thermodynamics of the anhydrate/dihydrate carbamazepine (CBZA/CBZH) in ethanol-water mixtures was studied by measuring the solubility of anhydrate and dihydrate carbamazepine at 0-60 °C. Both stable form solubility and metastable form solubility were measured, the latter with the assistance of Raman immersion probe. The thermodynamic properties of the anhydrate/dihydrate system, such as the relative stability, and enthalpy and entropy of dissolution, were estimated by plotting the measured solubility data according to the van't Hoff equation. The anhydrate/dihydrate carbamazepine showed an enantiotropic relationship in the studied mixtures and temperature ranges. It was shown that at a certain temperature, there was an equilibrium water activity value at which the anhydrate and dihydrate carbamazepine were in equilibrium. This equilibrium water activity value depends significantly on the temperature. The lower the temperature, the smaller is the water activity value needed to attain equilibrium between anhydrate and dihydrate. The obtained results are useful in determining crystallization parameters to achieve a desired anhydrate or hydrate phase. The approach can be applied to other anhydrate and hydrate systems.

Details

Original languageEnglish
Pages (from-to)101-107
Number of pages7
JournalInternational Journal of Pharmaceutics
Volume321
Issue number1-2
Publication statusPublished - 14 Sep 2006
MoE publication typeA1 Journal article-refereed

    Research areas

  • Carbamazepine, Hydrate, Metastable solubility, Phase transition, Solubility, Water activity

ID: 10773105