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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

PXRD patterns of theophylline processed at 3.8% RH and 20°C.
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fig6: PXRD patterns of theophylline processed at 3.8% RH and 20°C.

Mentions: The evolution of PXRD patterns of theophylline during processing at 3.8% and 20°C (conditions which favor the occurrence of the anhydrous metastable form) is presented in Figure 6. The pattern after 12 hours corresponds to a mixture of the monohydrate M, the metastable anhydrate III [12], and stable anhydrate II but with a prevalence of form III. One can observe in this pattern that the most noticeable characteristic peaks are those of the form III (9.4, 11.3, 12.5, and 15.4°2θ).


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)

PXRD patterns of theophylline processed at 3.8% RH and 20°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4595972&req=5

fig6: PXRD patterns of theophylline processed at 3.8% RH and 20°C.
Mentions: The evolution of PXRD patterns of theophylline during processing at 3.8% and 20°C (conditions which favor the occurrence of the anhydrous metastable form) is presented in Figure 6. The pattern after 12 hours corresponds to a mixture of the monohydrate M, the metastable anhydrate III [12], and stable anhydrate II but with a prevalence of form III. One can observe in this pattern that the most noticeable characteristic peaks are those of the form III (9.4, 11.3, 12.5, and 15.4°2θ).

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