1. To what degree can a chromatographic procedure be modified and still be in compliance? Can column length, internal diameter, mobile phase composition be modified?

    Chromatography <621> contains a list of allowed adjustments to chromatographic systems. However, the user should verify the suitability of the method under the new conditions by assessing the relevant analytical performance characteristics potentially affected by the change (see section System Suitability under Chromatography <621>).

  2. What brand of HPLC/GC column was used in the development and/or validation of a particular test? Is there an alternative chromatographic column for a particular test?

    The information about the brand of HPLC Columns, used for the development of USP–NF methods, is available in the electronic version of the USP–NF under Chromatographic Columns. The link to the information is at the end of each monograph. The complete database, called Chromatographic Columns could also be searched through a Quick Search, or through ‘Advanced Search’ under ‘General’. Print copies of the publication "Chromatographic Columns" are available through USP Customer Service: phone 301-881-0666 or Please note that the identification of chromatographic column reagents by brand name is provided solely for informational purposes as a matter of convenience, without implication or approval, endorsement, or certification. In addition, the omission of a particular brand or product does not indicate that the article was judged to be unsatisfactory or inadequate. This response has been provided for informational purposes only, and should not be construed as an official interpretation of USP text, or be relied on to demonstrate compliance with USP standards or requirements.

  3. How much deviation is allowed from a relative retention time prescribed in a monograph?

    From <621>, the deviations of relative retention time values measured for the test substance from the values obtained for the reference compound and mixture should not exceed the reliability estimates determined statistically from replicate assays of the reference compound. Also, relative retention times may be provided in monographs for informational purposes only, to aid in peak identification. There are no acceptance criteria applied to relative retention times.

  4. Can a USP scientist analyze/interpret spectra/chromatograms/data?

    USP scientists cannot review and interpret data, per the Official Statements and Interpretations policy: “USP shall not provide an official opinion as to whether a particular article does or does not comply with compendial requirements, except as part of an established USP verification or other conformity assessment program that is conducted separately from and independent of USP's standards-setting activities.”