Experimental Aspects of Measuring the Vial Heat Transfer Coefficient in Pharmaceutical Freeze Drying

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SP Scientific

To view the full webinar, please visit: http://www.spscientific.com/WebinarDetail.aspx?id=3680 One of the current methods for cycle optimization in primary drying to is develop a design space based on quality by design (QbD). In order to calculate the design space the vial heat transfer coefficient (Kv) is needed. This value can be obtained relatively easily by probing the sublimation rate from the vials at different chamber pressures. However, this value is an average value for the whole shelf of vials. This study has determined that there is a large range of Kv values depending on the vials placement on the shelf. The further the shelf temperature from ambient the larger the edge effect (and hence the larger the range). Additionally, at low temperatures the effect of chamber pressure is more significant and leads to a larger increase in the edge effect compared to shelf temperature closer to ambient. These large ranges of Kv can significantly alter the design space such that edge vial have the propensity to fail. Another factor found important when determining Kv is importance in having all the vials open (ie. the thermocouple is held in place such that the opening is not obstructed), or have all the vials partially stoppered and use thermocouple with a thermocouple holder. Being aware of these effects on the vial heat coefficient will lead to a better design spaces and understanding of the primary drying cycle. Presented by: Lindsay Wegiel