Determining the Density and Moisture Content of Powders Using Microwave Dielectric Spectroscopy
Talesha T. Hall and Michael T. Harris. Chemical Engineering, Purdue University, 480 Stadium Mall Drive, FRNY 3007, West Lafayette, IN 47907
The pharmaceutical industry provides a significant opportunity to derive value by focusing on improvements in development and manufacturing. One improvement that could transform the way in which drugs are manufactured is the development of continuous manufacturing processes, as opposed to the typical batch processes currently used in the industry. The emergence of continuous processes requires the development of new sensors that can be easily integrated into equipment currently being used in industry. These sensors need to have the ability to monitor and control bulk flow properties. Fundamental limitations of most existing sensors reside in the lack of transferability of calibration across instruments and the need for individual calibration for each type of material. Some of the reasons are related to the fact that these calibrations are often established for instrument specific parameters. They are based on statistical analysis and lack any physical foundations. The transformative impact lies in understanding material properties at a fundamental level and using that information to develop new sensors and/or configurations of existing sensors. In this study, a dielectric probe in conjunction with a microwave network analyzer was used to establish fundamental relationships between density, moisture content, and the dielectric properties of common pharmaceutical excipients. This microwave probe method allows the monitoring of both density and moisture content using one device. This is an important asset because both of these physical properties, density and moisture content, were found to be important in controlling the drug dosage during the manufacturing of tablets.