USP Chapter <645> 'Water Conductivity' Revised

The recently issued second supplement to USP 31 (2008), the American Pharmacopoeia, includes the revised Chapter <645> on conductivity measurement. We already reported about the upcoming revision, which was published in the NF Pharmacopoeial Forum, in 2007.

As expected, the advantages of online measurement are clearly pointed out in the revision. This addition goes back to the FDA's wish and eventually represents a way of implementing FDA's initiative 'cGMPs for the 21st Century'.
Apart from that, the text mentions problems that can occur in samples taken offline due to the sampling method, environment and sampling containers, e.g. with regard to the CO2 content.

The methods to be applied are divided into the sections

  • Bulk Water (for purified water, WFI, condensate, pure steam, etc.) and
  • Packaged Water (for highly purified water, sterile water for inhalation, etc.)

This subdivision is new and has been introduced because of sample preparation and a distinction of conductivity requirements depending on the container volume of packaged water.

An important extension can be seen in the introduction of a further verification step meant to ensure the use of a device correctly calibrated for the lower measuring range.

Dr Robert Eicher
On behalf of the European Compliance Academy (ECA)

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