KERN offers the testing and determination of the minimum sample weight according to United States Pharmacopeia (USP) chapter 41 and European Pharmacopoeia (Ph.Eur.) chapter 2.1.7 as a service.
In the following, we explain the differences between the two variants of the minimum sample weight:

European Pharmacopoeia (Ph.Eur.)

The European Pharmacopoeia (Ph.Eur. for short) is the only reference work for the quality control of medicinal products in Europe. It is therefore binding for all pharmaceutical companies wishing to export medicinal products to the European market. It is legally binding in a similar way to its American counterpart USP (United States Pharmacopeia) and also has similar requirements.

The Ph. Eur. Chapter 2.1.7, however, explicitly states that a calibration should include the uncertainty of measurement and emphasizes the importance of as-found and as-left calibration. In addition, the test and determination differs in that according to USP a test of the accuracy and according to Ph.Eur a test of the sensitivity of the balance is performed.

The requirements of the German Pharmacopoeia are defined in chapter 2.1.7 of Ph.Eur., which is legally binding since 01.01.2022:

• Repeatability
• Sensitivity

These specifications are used to calculate the minimum sample weight of the balance, i.e. the smallest sample weight that may be measured on the balance.

United States Pharmacopeia (USP)

The USP is the American equivalent of the German Pharmacopoeia and is also used as a guide by many companies in Germany. The requirements of the USP for balances are set out in two chapters:

• Chapter 41 is binding and includes requirements for:
  
  • Repeatability
  • Accuracy
  These specifications are used to calculate the minimum sample weight of the balance, i.e. the smallest sample weight that may be measured on the balance.
  
  
• Chapter 1251 is not mandatory and includes recommendations on installation location and also suggestions for regular (e.g. annual) testing of scales as part of a "Performance Qualification" (pQ). This includes further tests and acceptance criteria for:
  
  • Eccentric load
  • Linearity
  These additional tests correspond to a DAkkS calibration.

Compared to the minimum sample weight as an attachment to the DAkkS calibration certificate, only repeatability is taken into account for the minimum sample weight according to USP/Ph.Eur..

In the DAkkS calibration certificate, parameters such as off-center load or linearity are taken into account in addition to the accuracy of use on which the minimum initial sample weight is based. However, these have only a minor influence with small initial weights.

Can we assist you with compliant weighing?

Then please contact us for testing and determination of the minimum weight according to Ph.Eur. and/or USP:

+49 7433 9933-400

testservices-onsite@kern-sohn.com