Monitoring dehydration kinetics using simultaneous thermal and spectral methods

Abstract

AbstractThe dehydration kinetics of theophylline monohydrate is a two‐stage process. The first stage involves loosening of the crystal water followed by a second stage in which the water evaporates from the sample. During differential scanning calorimetry (DSC) measurements, the kinetics of the two stages can be dramatically altered because of the sample environment and DSC pan type. In‐depth understanding of how the sample environment alters the dehydration process and the kinetics involved requires more than DSC experiments alone. This paper describes the use of a novel, simultaneous thermal and spectral technique to monitor the dehydration kinetics of theophylline monohydrate. The analysis of the results obtained on the combined DSC‐near‐infrared and DSC‐Raman equipment clearly detects the two stages of the dehydration process and the polymorphic structural changes that take place. The combined technique provides a powerful method to monitor the dehydration of hydrous systems. Copyright © 2010 John Wiley & Sons, Ltd.