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Organic Impurities Procedures: Format Change for Presenting Relative Retention Times

Type of Posting: General Announcement
Posting Date: 29-Oct-2021

This notice announces a format change for presenting relative retention times within Organic Impurities procedures in USP-NF monographs. According to USP’s current style, monographs have typically co-located the impurity name; its relative retention time; its acceptance criterion; and its relative response factor, if applicable, in a single table within the Acceptance Criteria subsection. Impurities and/or other compounds with no specified acceptance criteria have also been included in the same table as an aid to peak assignment, and when this was the case, instructions in a footnote were usually provided to exclude these impurities from being reported or included in the total degradation products or total impurities.

USP is implementing the following format changes for Organic Impurities procedures in new and revised USP-NF monographs:

  1. The table within the Acceptance criteria subsection will no longer include any compound that does not have a specified acceptance criterion.
  2. The table within the Acceptance criteria subsection will continue to list limits for specified impurities or specified degradation products, Any unspecified impurity or Any unspecified degradation product, and Total impurities or Total degradation products, as appropriate. Relative response factors will also be listed in this table, when applicable. 
  3. A separate table will provide relative retention times, as information that could aid in peak assignment, for all compounds of interest (when the information is available to USP), including specified impurities or specified degradation products; counterion(s) of the active pharmaceutical ingredients (APIs); compounds used for system suitability evaluation; internal standards; and identified impurities with no specified limits (e.g., process impurities in some drug product monographs). This table will be located within the System suitability subsection of the test.  

The impurity profile presented in a monograph is based on available information representing one or more approved drug product. This impurity profile may not be applicable to all approved products. It is incumbent upon the manufacturer to characterize, by appropriate means, the impurity profile of their product to establish those process impurities and/or degradation products that may be present.

USP will implement this change as monographs come up for In-Process Revision but will not revise monographs exclusively for the purpose of implementing this format change .  New and revised monographs with the new format will go through the Pharmacopeial Forum (PF) process for public comment. The format change will be introduced over the next several PFs in monograph proposals containing organic impurities acceptance criteria that are amenable to this change.  

Refer to FAQs: Organic Impurities for answers to some frequently asked questions about organic impurities tests for drug substances and drug products, and related concepts. Should you have any questions, please contact USP Monographs representative.