USP Chapter 41 Weighing Requirements

USP Chapter 41 Weighing Requirements

Weighing affects the entire analytical workflow process––any error in the process can lead to inaccurate results. To avoid errors during the weighing process, the United States Pharmacopeia (USP) has rigid measurement requirements for balances for weighing analytes and quantitative measures. 

These unyielding requirements are applicable to all pharmaceutical QC activities globally, not just exclusively in the United States. The General Chapter 41 “Balances” describes requirements that a balance must meet when weighing analytes for quantitative measures. USP Chapter 41 weighing requirements are an integral part in the pharmaceutical quality control laboratory. 

For a balance to conform to the revisions, it must meet three requirements:

  • Accuracy. In order for a balance to satisfy its conditions, it must provide accuracy. Accuracy is usually assessed during a test with a specific acceptance criteria. 
  • Repeatability. As described in Chapter 1251, the concept of minimum weight in Chapter 41 is being made mandatory
  • Calibration. The balance must be calibrated––tested for accuracy––periodically before it is used for quality-relevant measurements. 

The new weighing requirements review the USP revisions and explain what changes mean for daily lab procedures, including details on repeatability and accuracy testing. To ensure that an instrument is accurate and consistent, it’s important that you practice routine tests. 

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