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This white paper discusses the USP <645> water conductivity regulations for pharmaceutical bulk waters: Water for Injection (WFI), Purified Water (PW), and Pure Steam condensate. It covers the advantages of performing on-line testing over off-line testing and the importance of temperature compensation in conductivity measurements.
The three-stage test method for USP <645>, which covers both on-line and off-line testing, is explained in detail. The calibration requirements for conductivity sensor measuring electronics or transmitter, the sensor itself, and cable linking the sensor and transmitter are discussed, along with the recommended process for calibration.
The paper also presents the requirements for transmitters or measurement electronics and the sensors, such as cell constant and temperature accuracy, calibration traceability to ASTM or NIST, and resolution of display.
The UniCond conductivity/resistivity sensor, which integrates the measuring circuit and physical sensor into a single unit, is introduced as a system that is factory calibrated and meets the USP <645> water conductivity regulations compliance. Lastly, the USP <1644> test chapter, released in 2017, is mentioned as providing technical guidance for conductivity measurement systems.
