FAQs: <621> Chromatography

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 General Chapter <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 most updated information on the brand name of the column used to validate any chromatographic procedure in USP—NF, together with possible alternatives, where applicable are available at the following www.uspchromcolumns.com.

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.