New USP proposal for updating identity checks in U.S. Pharmacopeia

Recommendation
10/11 September 2025
In the Pharmacopeial Forum 41(2), an article entitled 'Stimuli to the Revision Process' on the modernisation of the general chapter on identity checks <191> has been published in USP/NF. The same issue of PF 41(2) also contains the proposal to revise this existing general chapter <191>.
The chapter <191> treats the identification of ions or counterions in active substances that exist as salt compounds. The plan is to replace the existing flame test from <191> since it is not particularly meaningful. In future, selecting the options for identity checks in chapter <191> will be more flexible. Users will be able to apply other methods as long as they have been properly validated.
The following instrumental methods are being considered:
- X-ray fluorescence (XRF)
- Atom spectrometry (AA)
- ICP-OES
- ICP-MS
- IR
- Raman
- Ion chromatography
Other methods can also be used. However, the prerequisite here is that the user must document the specificity of a method as part of the validation.
For detailed information on the USP proposal, please see the USP website of Pharmacopeial Forum (PF).
Source: USP
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