Mettler Toledo’s GWP weighing standard ensures USP compliance

The firm is offering a free on-demand webinar to clarify the new rules

USP has revised mandatory Chapter 41 on balances and Mettler Toledo says its global weighing standard can help pharmaceutical manufacturers meet requirements

United States Pharmacopeia (USP) published the revised mandatory Chapter 41 on balances in June, as well as new updates to the advisory Chapter 1251. With just six months to comply, Mettler Toledo says its global weighing standard, GWP, can help pharmaceutical manufacturers and suppliers to meet the new requirements.

The new revisions define modified balance test procedures for the US pharmaceutical industry and also apply to companies exporting to the US. With the revised chapters becoming official on 1 December, Mettler Toledo is providing a free on-demand webinar to explain how balance quality management will be affected, focusing on the determination of minimum weight and execution of routine testing. In addition, the firm is offering information on its website including a free white paper and a video, as well as the opportunity to register for an easy e-learning course.

For a long time balance users and manufacturers argued that balance assessment as per USP’s General Chapter 41 (‘Balances’) was unclear and difficult to comply with. In addition, they frequently commented that General Chapter 1251 (‘Weighing on an Analytical Balance’) no longer represented state-of-the-art weighing practices.

GWP Verification is a risk-based service that helps eliminate redundant or erroneous testing

The revisions to both chapters in the Second Supplement to USP 36-NF 31 aim to help US pharmaceutical manufacturers and suppliers ensure accuracy and eliminate costly over-testing. Mettler Toledo says its GWP can help consumers put the new standards into practice in a structured and effective way.

The new requirements of General Chapter 41 are mandatory. The revised chapter details a relatively demanding balance assessment, outlining accuracy and repeatability tests for calibrated balances used to weigh analytes for quantitative measures. Since accuracy can only be gauged using weights that are at least 5% of an instrument’s capacity, test weight selection criteria have also been modified accordingly (weights smaller than 5% cannot assess systematic deviations sufficiently well enough).

General Chapter 1251 provides additional clarification on the new procedures and extends the scope to any balance used for an analytical procedure. It details that balance performance verification should be carried out using a risk-based approach. It is recommended only to weigh net samples that weigh sufficiently more than the minimum weight to account for fluctuations in the balance's performance due to varying influences from the environment and the balance operators. This requirement is clearly applied to the sample weight itself – and not to the tare vessel. Additionally, daily testing recommendations have been dropped. This change is expected to provide significant timesavings which, if accompanied by weighing accuracy, will also offer monetary savings.

Tailored to each weighing application, Mettler Toledo says GWP Verification is a risk-based service that helps eliminate redundant or erroneous testing. Thanks to determining the minimum weight and measurement uncertainty for each and every balance and scale used in the weighing process, manufacturers not only optimise SOPs, ensure consistent product quality and pass air-tight audits, they also avoid potentially costly litigation and fines resulting from a poorly-formulated, out-of-specification product.

Mettler Toledo’s free webinar explaining the implications of the new USP revisions can be viewed at:

More information is available at