Single-vial monitoring

The various techniques available to monitor the primary drying can be roughly divided into three groups as they can be used to monitor single vials, a group of vials or the whole batch (Barresi et al, 2009a) these techniques will be discussed and compared in the following sections. 

Besides spectroscopy methods, other techniques have also been proposed for the in-line monitoring of the water content in single vials among them, dielectric measurements (Suherman et al, 2002) seem the most promising, at least for detection of the endpoint the electrodes can be placed outside the vial to reduce interference with the process. Monitoring of electric properties, and in particular of the product resistance (or inductance), has also been proposed. The technique seems suitable especially for substances that show a sharp eutectic melting, as in this case... 

While the sensors described in the previous paragraph allow monitoring of only single vials, a balance placed directly in the vacuum chamber of the freeze-dryer allows monitoring of a group of vials the direct weight measurement enables the... 

The sample rack is unique in that it possesses pitch both front to back and side to side. A single robot pick-up point is defined, and an optical (IR) sensor constantly monitors the pick-up point for the presence of a sample. Vials placed in the rack roll down to the pickup point, under the influence of gravity. The rack allows implementation of a novel processing scheme. 

---