Revised USP Chapter <831> Refractive Index Published again for Comments

In the Pharmacopeial Forum, PF 48(3), a new proposal of USP Chapter <831> Refractive Index has been published for comments.

The text has been revised again to take into account the comments received on the previous proposal published in PF 47(3). Therefore, the previous proposal has been canceled.

According to the briefing notes, the revisions to the chapter include, besides minor editorial change, the following:

• Add a specification for an apparatus that provides a means of operation at the prescribed temperature with readings to at least ±0.1°.
• Add a specification for a certified reference material used that must have an equal or better expanded uncertainty than ±0.001.
• Add operational qualification requirements for accuracy that state that the measurement of a certified reference material should agree with the stated certified value within the limits of the expanded uncertainty of the reference material added to the performance specification of the instrument. In some cases, additional uncertainty components may be added to the uncertainty acceptance criteria, including temperature uncertainty or repeatability uncertainty. These components may be included at the user's discretion based on the intended use of the system.
• Revise the repeatability requirements for operational qualification to be determined using six replicate measurements and an acceptance criteria established based on the stated repeatability performance specification of the instrument.
• Clarify the performance qualification requirements, clarifying the frequency of testing and the suitability of reference materials used.

The deadline for submitting comments is July 31, 2022.

The draft of the revised chapter is available on PF Online. (Please note: a one-time registration is required to access the Pharmacopeial Forum.)