USP <645> Water Conductivity

USP<645> details the proper measurement of pharmaceutical bulk water ionic conductivity based on sodium chloride model. Instruments must be accurate to ± 0.1 µS/cm or better and cell constant of ± 2%. All instruments must be calibrated with NIST-traceable resistors accurate to ± 0.1% of value. All values obtained are uncompensated for temperature and compared against a table of values at defined temperatures.

USP <645> describes three types of possible measurements:

Stage 1: Online or closed container (most commonly used)

Stage 2: Open container (lab)

Stage 3: Chemical-added pH measurement determination

The Hach Ultra Anatel line of TOC analyzers meet and/or exceed all requirements of USP <645>.