Development of a prototype capacitive balance for freeze-drying studies

A capacitive balance that is able to work in the severe environment of a fr eeze-drying process has been conceived, constructed and tested. The influen ce of temperature variations had to be taken into account: a model of the i nstrument which makes use of the temperature of several components measured by three thermocouples was developed to correct the frequency signal gener ated by the device and to convert it into mass; the model parameters were i dentified by a least-squares method from blank lyophilisation runs. This ba lance offers the possibility of optimising the freeze-drying process throug h the accurate investigation of the process kinetics. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.