In dielectric spectroscopy, a technique traditionally used to characterize molecular mobility in polymers, the sample is usually analyzed as a thin film. In recent years, the technique has been extended to characterize both drug substances and drug products and has revealed a correlation between molecular mobility and stability. However, for pharmaceutical systems, analysis of powders is strongly preferred over films. Therefore, the dielectric behavior of several compounds of pharmaceutical interest-nifedipine, indomethacin, itraconazole, and griseofulvin-obtained using powder and film samples were compared. The magnitudes of the intrinsic dielectric properties were affected by the sample configuration with the powder samples consistently yielding lower values. The use of effective medium theories enabled us to account for the effect of air in the powder samples. The relaxation time, a property of immense importance to the pharmaceutical community, was not influenced by the sample configuration.
Bibliographical noteFunding Information:
We are grateful to Prof. Gregory McKenna, Prof Ronald Siegel, Dr. Sarat Mohapatra, and Dr. Sunny Bhardwaj for their valuable comments. Khushboo Kothari was partially supported by the Center for Pharmaceutical Processing and Research and Doctoral Dissertation Fellowship, University of Minnesota. The project was partially funded by the William and Mildred Peters endowment fund.
© 2014 Wiley Periodicals Inc. and the American Pharmacists Association.
Copyright 2017 Elsevier B.V., All rights reserved.
- Relaxation time
- Solid state