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

Touil A, Peczalski R, Timoumi S, Zagrouba F - J Pharm (Cairo) (2012)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Ecole Nationale d'Ingénieurs de Gabès (ENIG), Université de Gabès, rue Omar Ibn-Elkhattab, Gabès 6029, Tunisia.

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.

No MeSH data available.


Related in: MedlinePlus

Scanning electron micrographs of different phases of theophylline at 3.8% RH and 20°C. (a) 0 hours (monohydrate), (b) after 12 hours (metastable anhydrate), (c) after 24 hours (stable anhydrate), and (d) after 7 days (stable anhydrate).
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fig7: Scanning electron micrographs of different phases of theophylline at 3.8% RH and 20°C. (a) 0 hours (monohydrate), (b) after 12 hours (metastable anhydrate), (c) after 24 hours (stable anhydrate), and (d) after 7 days (stable anhydrate).

Mentions: The transition between the monohydrate and the metastable form corresponds to the reversible loss of water through channels in the crystal lattice according to Phadnis and Suryanarayanan [8]. The crystal lattice of the metastable form was observed to collapse with time to produce the anhydrous stable form (see Figure 7).


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

Touil A, Peczalski R, Timoumi S, Zagrouba F - J Pharm (Cairo) (2012)

Scanning electron micrographs of different phases of theophylline at 3.8% RH and 20°C. (a) 0 hours (monohydrate), (b) after 12 hours (metastable anhydrate), (c) after 24 hours (stable anhydrate), and (d) after 7 days (stable anhydrate).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4595972&req=5

fig7: Scanning electron micrographs of different phases of theophylline at 3.8% RH and 20°C. (a) 0 hours (monohydrate), (b) after 12 hours (metastable anhydrate), (c) after 24 hours (stable anhydrate), and (d) after 7 days (stable anhydrate).
Mentions: The transition between the monohydrate and the metastable form corresponds to the reversible loss of water through channels in the crystal lattice according to Phadnis and Suryanarayanan [8]. The crystal lattice of the metastable form was observed to collapse with time to produce the anhydrous stable form (see Figure 7).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Ecole Nationale d'Ingénieurs de Gabès (ENIG), Université de Gabès, rue Omar Ibn-Elkhattab, Gabès 6029, Tunisia.

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.

No MeSH data available.


Related in: MedlinePlus