Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2486641 | Journal of Pharmaceutical Sciences | 2011 | 15 Pages |
Abstract
The real (εâ²) and imaginary (εâ³) components of the complex permittivity of anhydrous lactose and microcrystalline cellulose (MCC) under different bulk densities, moisture contents (MCs), and times of hydration (for anhydrous lactose) were measured nondestructively using a microwave resonator sensor operating in the range of 700-800 MHz. Measurements of sensor resonant frequency and conductance allow, through calibration, determination of the complex dielectric properties εⲠ(relative permittivity) and εⳠ(relative dielectric loss) of the test material. Characteristic graphs of εⳠversus εâ²Â â 1 curve for each powder were generated as a function of bulk density and MC. Such data can be used to develop empirical models for the simultaneous in situ measurement of the bulk density and MC of the powders. Unlike MCC, anhydrous lactose is converted to its hydrate form in the presence of moisture, which causes a reduction in the amount of physisorbed and “free” water and a subsequent change in the dielectric properties. For powders such as anhydrous lactose that can form a crystal hydrate in the presence of moisture, a combination of techniques such as vibrational spectroscopy together with microwave resonator measurements are appropriate to characterize, in situ, the physical and chemical properties of the powder.
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Authors
Pei-Fang Sung, Yi-Ling Hsieh, Kristen Angonese, Don Dunn, Ray J. King, Rachel Machbitz, Andrew Christianson, William J. Chappell, Lynne S. Taylor, Michael T. Harris,