Moisture and temperature dependence of the dielectric properties of pharmaceutical powders

T. R. A. Magee, W. A. M. McMinn, G. Farrell, L. Topley, Y. S. Al-Degs, G. M. Walker, M. Khraisheh

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The dielectric properties of pharmaceutical powder-(paracetamol, aspirin, lactose, maize starch, adipic acid) solvent (water) mixtures were measured at 2,450 MHz at a range of moisture contents (0-1.0 kg kg(-1), dry basis) and temperatures (20-70 A degrees C). The dielectric constant (epsilon'), loss factor (epsilon aEuro(3)) and penetration depth (d (p)) were found to be dependent on frequency, moisture content, temperature and powder type. For powder-water mixtures, a linear increase in the dielectric properties with moisture content was observed, whilst the temperature dependence was of quadratic form. The penetration depth was also significantly affected by temperature and moisture content. Although, epsilon aEuro(3) also increased with increasing temperature, variation with moisture content was temperature dependent. This information on dielectric properties is essential for mathematical description of the pharmaceutical product temperature history during microwave heating and for the design of microwave drying equipment.

Original languageEnglish
Pages (from-to)2157-2164
JournalJournal of Thermal Analysis and Calorimetry
Issue number3
Early online date09 Oct 2012
Publication statusPublished - Mar 2013

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Copyright 2012 Elsevier B.V., All rights reserved.

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Magee, T. R. A., McMinn, W. A. M., Farrell, G., Topley, L., Al-Degs, Y. S., Walker, G. M., & Khraisheh, M. (2013). Moisture and temperature dependence of the dielectric properties of pharmaceutical powders. Journal of Thermal Analysis and Calorimetry, 111(3), 2157-2164.