Dielectric Spectroscopy: Choosing the Right Approach - Pharmaceutical Technology

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PharmTech Europe

Dielectric Spectroscopy: Choosing the Right Approach
This tutorial paper is meant to aid in dielectric-sensor selection

Pharmaceutical Technology
Volume 9, Issue 32, pp. 8293

Further reading

A significant amount of literature is available that describes the theoretical aspects of dielectric behavior, algorithms, and signal processing methods used for the processsing of dielectric data and sensor design for dielectric measurements. One of the earliest models describing the frequency dependence of dielectric behavior was proposed by Debye (43). Jonscher describes dielectric relaxation emphasizing solids materials (44). Dielectric spectroscopy also has been explored in detail for polymeric materials (36). An understanding of dielectric behavior for engineers is presented by Coelho (45). Specifically for pharmaceuticals, a comprehensive review of applications is provided by Craig (14). MacDonald provides a review of methods for measurement of dielectric properties (46). A number of algorithms have been proposed for calibration and correlating data to physical property distributions (47–49). Rapid advancements in microtechnology have resulted in an increase in the number and complexity of electrode structures available for dielectric measurements. Notable references for sensor design are also available (50–56). A comprehensive overview of interdigital dielectric sensors is provided by Sundara-Rajan (57). A detailed review of currently available dielectric spectroscopic systems can be found at http://www.ee.washington.edu/research/seal/pharmatech/.

A. Mathur is a graduate student, K. Sundara-Rajan* is a PhD candidate, G. Rowe is a PhD candidate, and A. V. Mamishev is an associate professor at the Sensors, Energy, and Automation Laboratory, Department of Electrical Engineering, University of Washington, Seattle, tel. 206.351.8101,

*To whom all correspondence should be addressed.

Submitted: Oct. 22, 2007. Accepted: Jan. 15, 2008


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5. A.G. Ozturk et al., "Mechanism of Release From Pellets Coated With An Ethylcellulose-Based Film," J. Controlled Release 14 (3), 203–213 (1990).

6. K.E. Peiponen et al., "Optical Coating Inspection of Pharmaceutical Tablets by Diffractive Element," Measure. Sci. Technol. 8 (7), 815–818 (1997).

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8. H. Wikstrom, P.J. Marsac, and L.S. Taylor, "In-Line Monitoring of Hydrate Formation During Wet Granulation Using Raman Spectroscopy," J. Pharm. Sci. 94 (1), 209–219 (2005).


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