New Proposals for Analytical Balances and Quality-Relevant Weighing Processes in the American Pharmacopoeia
The repeatability of the measurements must be smaller than 0.1 %.
The accuracy (verification through certified OIML or ASTM weights) must be better than 0.1 % (new!).
Short weight check (new!).
In determining the repeatability, the hitherto used expansion factor k=3 is now replaced by an expansion factor k=2. As a direct consequence of this, the minimum sample weight for the quality-relevant weighings affected by USP <41> is reduced by one third.
The emphasis of the new draft is on the routine operation of the balance: Typically, repeatability and accuracy are assessed before the balance is put into operation (e.g. during IQ, OQ, PQ) and afterwards periodically, in accordance with the effective SOPs. Usually, a weight check with internal or external check weights is conducted on every day on which the balance is used or in other appropriate intervals defined by the laboratory in SOPs.
<1251> Weighing on an Analytical Balance
The draft for this General Chapter was harmonised with the new proposal for Chapter USP <41>. The formerly effective General Chapter USP <1251> should be deleted entirely and replaced by a completely new text.
The new draft includes among others the following sub-topics:
Here, attention should be paid to the fact that General Chapter USP <41> is mandatory for quality-relevant tests within the framework of USP's scope of application, whereas the Chapter USP <1251> merely represents a recommendation and gives additional pieces of advice not mentioned in Chapter USP <41>.
The deadline for commenting both of the new drafts was 15 October 2007. It is to be expected that revised drafts for the two new chapters will be published in the Pharmacopeial Forum in the first quarter of 2008