18 common questions about the new European Pharmacopoeia (Ph.Eur.) Chapter 2.1.7

1. When will the new chapter 2.1.7 “Balances for Analytical Purposes” take effect, and what are the weighing tasks affected?

The new chapter was released in, July 2021 and became effective from January 1st, 2022. The new chapter is essential for any analytical weighing procedure detailed in a Ph.Eur. monograph.

2. What does the European Pharmacopoeia detail and how does this new chapter impact users?

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The European Directorate for the Quality of Medicines & Healthcare (EDQM) published the Ph.Eur. It is “a single reference work for the quality control of medicines in the signatory states of the Convention on its elaboration.”

The European Pharmacopoeia is a compilation of monographs elucidating quality standards for dosage forms, ingredients and analysis techniques for medicines (both human and veterinary use). These standards affirm the quality of pharmaceutical products.

The Ph.Eur. is the legally binding reference for all pharmaceutical companies that are placing pharmaceutical products in the European member states’ market.

This indicates that it is relevant not only for European pharmaceutical companies but also for companies that are producers of medicines and/or substances for pharmaceutical exporting to the European market.

Chapter 2.1.7 impacts companies in these particular industries if they utilize “balances for analytical purposes.”

3. Are there any specific requirements for making a balance model compliant with the European Pharmacopoeia’s chapter 2.1.7?

There is no specific mention in the Ph.Eur. that determines whether a particular balance model is compliant or non-compliant with chapter 2.1.7. However, there are some general requirements in chapter 2.1.7, such as ensuring “that the installation and operating conditions do not have a negative impact on the performance of the balance.”

The only specific requirement is that the balance must be grounded, which is usually accomplished through the electrical supply in modern models.

4. What is the meaning behind “analytical purposes?” Is the regulation applicable to preparational weighings (for instance, preparing buffer solutions)?

The chapter states, “Any weighings performed as part of tests prescribed to establish compliance with a monograph of the Ph.Eur. must be carried out according to the principles outlined in this chapter.”

Users should consider this statement when determining whether a balance is affected and if in doubt, determine whether the weighing result is truly relevant for assessing compliance with the corresponding monograph.

It should also be noted that the new chapter of the European Pharmacopoeia may have an impact on the preparation of a buffer solution.

5. What are the requirements for the calibration of a balance in chapter 2.1.7?

A relationship between the known value of test weights and the associated indicated value of the balance is established during calibration. According to the chapter, “…instruments must be periodically calibrated […] by the user or by a suitable competent body.”

Chapter 2.1.7 of the Ph.Eur. enlists three requirements:

  1. Calibration must establish measurement results’ traceability to SI units.
  2. The calibration results must be accompanied by measurement uncertainty.
  3. Before any maintenance operation that considerably distorts measurements, it is recommended to perform an “as found” calibration, followed by a second calibration (“as left”). Repairs, mechanical adjustments and transfer of the balance to another location are all considered significant operations in chapter 2.1.7.

The calibrations should be carried out by an accredited calibration lab, as competence is ensured by accreditation, and the above requirements should be met.

6. How does the Cubis® II lab balance from Sartorius help comply with the European Pharmacopoeia's chapter 2.1.7?

Customers can use the pharma software package for Cubis® II balances to meet the requirements of both the new Ph.Eur. chapter 2.1.7 and the USP, chapter 41.

The USP Advanced QApp analyzes the performance of balances and provides a guided workflow for determining the minimum sample weight in accordance with USP chapter 41 or the new Ph.Eur. chapter 2.1.7.

The minimum weight application keeps track of the weight determined by the USP Advanced QApp and compares it to allowable ranges based on various guidelines. These apps can be used in conjunction with advanced software programs for calculating and monitoring measurement uncertainty.

7. What is the purpose of the performance checks required by chapter 2.1.7 of the European Pharmacopoeia?

Performance checks estimate the random and systematic error of a balance. These checks concentrate on repeatability and sensitivity.

8. What are the repeatability and sensitivity requirements?

A single-piece test load of no more than 5% of the balance’s maximum capacity, but at least 100 mg, is used for the repeatability check. This weight is placed on the weighing pan at least 10 times.

The balance is reset to zero before each measurement. The repeatability is satisfactory if two times the standard deviation of the measured values divided by the smallest net weight defined by the user is not greater than 0.10 %. 

When the standard deviation (s) is less than 0.41 × d (where d is the balance’s actual scale interval), s is replaced by 0.41 × d.

A single-piece test load with a weight between 5% and 100% of the balance’s capacity is placed on the balance for the sensitivity check. If the difference between the balance’s indicated value and the nominal weight of the test load (or its conventional mass) is not more than 0.05 percent, the sensitivity is satisfactory.

9. In compliance with chapter 2.1.7 of the European Pharmacopoeia, what is the smallest possible sample weight that can be weighed?

On a balance, the smallest possible sample weight, or minimum sample weight (mmin), is 2000 times the standard deviation of the repeatability measurement. Therefore, if the standard deviation s is, for instance, s = 0.00015 g, the smallest sample weight that can be weighed is mmin = 0.3000 g = 300 mg.

The additional requirement of replacing the determined standard deviation with 0.41 × d, in instances where the standard deviation is less than 0.41 × d (where d is the actual scale interval of the balance), sets the smallest possible sample weight that can be weighed on a balance at 820 × d.

This indicates that the smallest possible minimum sample weight for a four-digit analytical balance with d = 0.0001 g, for instance, can never be less than 0.0820 g or 82 mg.

10. Is it possible to weigh smaller samples on the balance with a tare weight that is greater than the minimum weight?

The mass of a tare vessel is not taken into account when determining the minimum sample weight. This means that, regardless of the tare load, the minimum sample weight applies to net loads over the balance’s entire weighing range. The net weight of each sample must be equal to or greater than the minimum sample weight, regardless of whether or not a tare vessel is used.

Please make sure to download the Pharmacopoeia Compliance Guide containing the full set of 18 FAQs for an in-depth discussion of Chapter 2.1.7 of the Ph.Eur.

About Sartorius Lab Instruments GmbH & Co. KG

The Sartorius Group is a leading international partner of life science research and the biopharmaceutical industry.

With innovative laboratory instruments and consumables, the Group’s Lab Products & Services Division concentrates on serving the needs of laboratories performing research and quality control at pharma and biopharma companies and those of academic research institutes.

The Bioprocess Solutions Division with its broad product portfolio focusing on single-use solutions helps customers to manufacture biotech medications and vaccines safely and efficiently. The Group has been annually growing by double digits on average and has been regularly expanding its portfolio by acquisitions of complementary technologies.

In fiscal 2021, the company earned sales revenue of some 3.45 billion euros. At the end of 2021, nearly 14,000 people were employed at the Group’s approximately 60 manufacturing and sales sites, serving customers around the globe. 

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Last updated: Apr 21, 2022 at 8:48 AM


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