(185c) Non-invasive, continuous, quantitative detection of powder level, mass holdup and moisture fraction in pharmaceutical GMP vessels

We describe a quantitative, non-invasive, GMP-compatible capacitance technique that enables implementation of continuous processing control in pharmaceutical metallic vessels. To illustrate the technique, we describe a probe producing a rapid signal that varies continuously with powder level and/or mass holdup in the metal feed tube of a tablet press. We outline the principle of the processing electronics, provide an algorithm for the accurate interpretation of its signals, pose general design guidelines for embedding the instrument in metal vessels, and show how the technique can be paired with another non-invasive reference probe to operate with varying powder blend and moisture. In this example, we illustrate a control strategy that keeps powder level constant in the feed tube. We also show how the same technique can be used to monitor concentration of water or other solvents by exploiting the corresponding changes in dielectric properties of pharmaceutical blends.