SUBLIMATION DURING LYOPHILIZATION DETECTED BY TEMPERATURE PROFILE ANDX-RAY TECHNIQUE

The goal of the investigation was to obtain a more precise picture of the processes in a vial during lyophilization. The sublimation front d uring freeze-drying of a mannitol solution could be inferred from a te mperature profile, according to which the ice sublimates mainly from t op to bottom, and, to a lesser extent, from outside to inside. These f indings contradict the previous assumption that the sublimation front proceeds symmetrically from all sides, in a spherical fashion. Apart f rom glass, other container materials (aluminium and plastic) were also tested. The process of sublimation is the same, except that aluminium speeds up the process of drying while the isolating plastic slows it down. In order to check these results, X-ray photographs were taken at different points of time during primary drying. They confirm the resu lts obtained from the temperature profile.