Impedance Spectroscopy: Recent Developments as a Process Analytical Technology for Pharmaceutical Freeze-Drying. Lyophilization Summit 13-14th February, Prague.

cite as:
Smith, G. (2019). Impedance Spectroscopy: Recent Developments as a Process Analytical Technology for Pharmaceutical Freeze-Drying. Podium presentation at Qepler Lyophilization Summit 13-14 Feb, Prague

Podium presentation describing the application of through vial impedance spectroscopy in the determination of nucleation temperatures and solidification end points. TVIS dielectric loss parameters Fpeak and Cpeak and the dielectric storage at low frequency (e.g. 10 or 100 Hz) appear to offer the opportunity for the registration of the nucleation point for the onset of ice growth. In addition the dielectric storage at high frequency (e.g. 200 kHz) shows little temperature sensitivity and so is an ideal measurement frequency for assessing the end point of ice solidification. Post solidification, the parameter log Fpeak can then be redeployed to determine the point at which all excess latent heat has left the sample and the product temperature then equilibrates with the shelf. This work paves the way for the determination of a new critical process parameter based on the time interval between ice growth onset and ice solidification end point (alongside the ice nucleation temperature).

Content of the presentation:
1. Introduction
2. Dielectric loss mechanisms
3. TVIS Theory
4. What frequency for what process?
5. Observations on ice (Ice nucleation and growth; ice solidification end point)