title: Dielectric spectroscopy of small molecule pharmaceuticals-effect of sample configuration.
abstract: 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.
authors.affiliation: Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota, 55455.
authors.forename: Khushboo
authors.initials: K
authors.lastname: Kothari
authors.forename: Vishard
authors.initials: V
authors.lastname: Ragoonanan
authors.forename: Raj
authors.initials: R
authors.lastname: Suryanarayanan
mesh_terms: D058266:Dielectric Spectroscopy / Q000379:methods*; D004364:Pharmaceutical Preparations; D033362:Powder Diffraction
chemical_list: D004364:Pharmaceutical Preparations
keywords: amorphous; mobility; relaxation time; solid state; spectroscopy