Standard PAT Instrumentation: Pressure Gauges and Vapor Pressure Sensors

Le résumé fourni par la source

Pressure measurement plays an essential role in pharmaceutical freeze-drying (FD), with the entire process, as well as all ancillary processes, being controlled with the help of various pressure sensors. This chapter provides an overview of pressure and vapor pressure measurement in pharmaceutical FD, highlighting their importance for process understanding and control. It introduces the principles of gas pressure, units, and the behavior of real versus ideal gases are introduced before describing standard pressure sensors used in lyophilization – particularly capacitance manometers and Pirani gauges – and their calibration, performance, and redundancy in GMP environments. The chapter then explores the thermodynamic basis of water vapor pressure, including Dalton's law, dew and frost points, and the Clausius–Clapeyron and Antoine equations linking vapor pressure and temperature. These relationships underpin key drying parameters such as sublimation rate, interface temperature, and collapse temperature. Finally, the measurement of water vapor pressure is discussed through chilled-mirror hygrometers, polymeric dew-point sensors, and spectroscopic techniques, providing comparative insight into their precision, limitations, and suitability for process monitoring and control.

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