Rapid determination of dry layer mass transfer resistance for various pharmaceutical formulations during primary drying using product temperature profiles
Abstract
Mass transfer resistance of the dry layer during the primary drying phase of a lyophilizaton cycle is probably the most important factor affecting maximum product temperature and drying time. Product resistance parameters should be determined for each formulation because of their dependence of formulation composition and concentration. The purpose of this study was to determine the dry layer mass transfer resistance, using a simple and rapid method, for various pharmaceutical formulations during primary drying in a laboratory dryer, using monitored product temperature profiles. The mathematical tools used for the determination were a primary drying simulation program in conjunction with Powell's optimization algorithm. For each formulation studied, primary drying was performed using a shelf temperature of -15 or -20 degrees C and the chamber pressure controlled at 100 mTorr (0.1 Torr). The product temperature profiles (T(b)) during primary drying were recorded and became the input data for the parameter estimation. The normalized product resistance, R(pN), as a function of the dry layer thickness, l, can be described by: R(pN) = R(0) + A(1)l/(1 + A(2)l), where the constants R(0), A(1) and A(2) are product resistance parameters ...Continue Reading
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