Title: Infrared thermography for monitoring of freeze-drying processes: instrumental developments and preliminary results
Citation: JOURNAL OF PHARMACEUTICAL SCIENCES vol. 103 no. 7 p. 2088–2097
Publication Year: 2014
JRC N°: JRC88873
ISSN: 0022-3549
URI: http://dx.doi.org/10.1002/jps.24017
DOI: 10.1002/jps.24017
Type: Articles in periodicals and books
Abstract: Coupling an infrared (IR) camera to a freeze dryer for on-line monitoring of freeze-drying cycles is described for the first time. Normally, product temperature is measured using a few invasive Pt-100 probes, resulting in poor spatial resolution. To overcome this, an IR camera was placed on a process-scale freeze dryer. Imaging took place every 120 s through a Germanium window comprising 30,000 measurement points obtained contact-free from −40◦C to 25◦C. Results are presented for an empty system, bulk drying of cheese slurry, and drying of 1 mL human serum in 150 vials. During freezing of the empty system, differences of more than 5◦C were measured on the shelf. Adding a tray to the empty system, a difference of more than 8◦C was observed. These temperature differences probably cause different ice structures affecting the drying speed during sublimation. A temperature difference of maximum 13◦C was observed in bulk mode during sublimation. When drying in vials, differences of more than 10◦C were observed. Gradually, the large temperature differences disappeared during secondary drying and products were transformed into uniformly dry cakes. The experimental data show that the IR camera is a highly versatile on-line monitoring tool for different kinds of freeze-drying processes.
JRC Directorate:Health, Consumers and Reference Materials

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