Use of the capacitance manometer gauge in vacuum freeze-drying.

Abstract

This paper discusses the effect of pressure on the lyophilization, or vacuum freeze-drying. process, and the various types of vacuum gauges typically used for such pressure measurements. Location of the gauge on the process system, sterilization procedures, potential chemical contaminants, measurement dependence on gas composition, and other unique requirements of the freezedrying process on vacuum gauges are outlined. Of particular significance for freezedrying. the capacitance manometer gauge is discussed in greater detail, including theory of operation, construction, accuracy, and operation and calibration procedures. A comparison study is made of a capacitance manometer, a Hg McLeod gauge, and a thermocouple gauge on a commercial lyophilization system. When operated and calibrated properly, the capacitance manometer provides the accurate, repeatable pressure measurements that are prerequisite to successful lyophilization.