Chapter 41, which covers the minimum accuracy of weights and balances used to perform assays, was one of a few that had remained unchanged for twenty years. With the help of panels of experts, USP regularly and frequently updates and modifies the standards it sets. While some have suggested that the modifications require the purchase of expensive new high resolution measuring equipment or services from outside parties, in fact many laboratories can easily and efficiently comply themselves, using their existing equipment-if they understand the nuances of Chapter 41 and follow a few simple guidelines. The actual results from the methods detailed in the new standard will likely be in a similar range as those in the previous standard, but the techniques required and the wording of the standards are a bit more complex. A global team of experts drafted the new version, which was recently approved for release by the USP and officially goes into effect in December 2013. The Chapter 41 standard, previously used in assays to determine drug content and potency, was last updated more than twenty years ago. Pharmacopeial Convention’s (USP) Chapter 41 1 minimum quality standards for weights and balances.

Additional information is presented in general information chapter Weighing on an Analytical Balance, appearing elsewhere in this issue of PF.Pharmaceutical manufacturing companies have been nervously awaiting the fallout from major modifications in the U.S. The use of 0.4d as the minimum repeatability value is taken from Guidelines on the Calibration of Non-Automatic Weighing Instruments, EURAMET/cg-18, v.03.0 (2011) and SIM Guidelines on the Calibration of Non-Automatic Weighing Instruments (2008), equation (7.1.1-12). Thus, from a practical perspective, the effective specification remains essentially unchanged. The repeatability requirement is similar to the one in the current chapter, but in order to reflect current metrology practices, the limit has been changed from 0.1% to 0.10% and the coverage factor has been changed from 3 to 2. In this new chapter, requirements for balances used for materials that must be accurately weighed are redefined in terms of repeatability and accuracy. The General Chapters-Physical Analysis Expert Committee proposes replacing the existing chapter Weights and Balances with a new chapter titled Balances.

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