In this work, the the influence of the position of the vial on the shelf of a laboratory lyophilizer on the lyophilization process was examined. A vial with a 5% mass fraction of sucrose in an aqueous solution was placed in six different places on the heating-cooling shelf of the lyophilizer. The temperature of the vial and the temperature and heat flux at the contact of the vial with the shelf were monitored during freezing, primary drying and secondary drying. The results showed a range of primary drying duration from 6,60 h to 7,20 h between individual vial positions, which confirms the inhomogeneity of the temperature field on the shelf of the laboratory lyophilizer. Based on the analysis performed, we propose that, in order to more accurately determine the primary drying time, the least favorable location should be determined for each lyophilizer, which is most exposed to external influences and thus exhibits the longest primary drying time.
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