Calorimetric and spatial characterization of polymorphic transitions in caffeine using quasi-isothermal MTDSC and localized thermomechanical analysis

Manduva, Radhesh, Kett, Vicky L., Banks, Simon R., Wood, John, Reading, Mike and Craig, Duncan (2008) Calorimetric and spatial characterization of polymorphic transitions in caffeine using quasi-isothermal MTDSC and localized thermomechanical analysis. Journal of Pharmaceutical Sciences, 97 (3). pp. 1285-1300. ISSN 0022-3549

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Abstract

We describe a novel integrated approach to the study of polymorphic transformation that includes quasi-isothermal modulated temperature differential scanning calorimetry (QI-MTDSC) and microthermal analysis (MTA), with a view to studying the thermal, kinetic and spatial characteristics of the process. Form II and I caffeine was prepared and conventional DSC and hot stage microscopy performed. The Form II to I transition at circa 413 K was associated with a change in crystal habit to needle shaped crystals. QI-MTDSC was used to measure the heat capacity of the system as a function of temperature, while MTA was able to spatially differentiate between the two polymorphs in compressed systems. We present a novel extension of the reduced temperature method whereby we apply it for the first time to linear rising temperature data corresponding to the transition; the analysis suggests a close approximation to Arrhenius behavior. We also describe a heat transfer model that allows calculation of the thermal gradients within a hermetically sealed pan for the first time. The combined approach has therefore allowed the characterization of the thermodynamics and kinetics of the transformation process as well as spatial identification of the distribution of the transformation in compressed systems.

Item Type: Article
Faculty \ School: Faculty of Science > School of Pharmacy
Related URLs:
Depositing User: Rachel Smith
Date Deposited: 08 Mar 2011 15:58
Last Modified: 21 Apr 2020 17:54
URI: https://ueaeprints.uea.ac.uk/id/eprint/25770
DOI: 10.1002/jps.21048

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