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Journal of Pharmaceutics
Volume 2013 (2013), Article ID 892632, 9 pages
http://dx.doi.org/10.1155/2013/892632
Research Article

Influence of Air Temperature and Humidity on Dehydration Equilibria and Kinetics of Theophylline

1Ecole Nationale d’Ingénieurs de Gabès (ENIG), Université de Gabès, rue Omar Ibn-Elkhattab, Gabès 6029, Tunisia
2Université de Lyon, Université Lyon 1, 69622 CNRS, UMR 5007, Laboratoire d’Automatique et Génie des Procédés (LAGEP), Campus de la Doua, bât. CPE, 3 rue Victor Grignard, 69616 Villeurbanne, France
3Institut Supérieur des Sciences Appliquées et de Technologie de Gabès (ISSAT), Université de Gabès, rue Omar Ibn El-Khatab, Gabès 6029, Tunisia
4Institut Supérieur des Sciences et Technologies de l’Environnement (ISSTE), Université 7 Novembre de Carthage, Technopôle de Borj Cédria, Hammam-Lif 1003, Tunisia

Received 17 August 2012; Accepted 30 October 2012

Academic Editor: Pornsak Sriamornsak

Copyright © 2013 Amira Touil et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The effect of hygrothermal conditions (air temperature and relative humidity) on the dehydration of theophylline monohydrate was investigated. Firstly, the equilibrium states of theophylline were investigated. The data from gravimetric analysis at constant temperature and humidity were reported as desorption isotherms. The PXRD analysis was used to identify the different polymorphic forms of theophylline: the monohydrate, the metastable anhydrate, and the stable anhydrate. Solid-solid phase diagrams for two processing times were proposed. Secondly, the dehydration kinetics were studied. The water content evolutions with time were recorded at several temperatures from 20°C to 80°C and several relative humidities from 4% to 50%. Different mathematical models were used to fit the experimental data. The spatially averaged solution of 2D Fickian transient diffusion equation best represented the water mass loss versus time experimental relationship. The dehydration rate constant was found to increase exponentially with air temperature and to decrease exponentially with air relative humidity.