USP <621> - Chromatography

What it says

General Chapter <621> sets general requirements for the chromatographic methods used in USP monographs, including liquid, gas and thin-layer chromatography. It defines the terms used, sets out system suitability requirements such as resolution, repeatability, tailing and sensitivity, and defines the adjustments to method parameters that are allowed without full revalidation.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• System suitability is a check that the whole system is performing adequately on the day of analysis. It does not replace method validation or instrument qualification, and failing it means the run cannot be used.
• Allowed adjustments, for example to column dimensions, particle size, flow rate, temperature, mobile phase composition and injection volume, stay within defined limits. Changes beyond those limits are method changes that need to be justified and validated.
• The chapter works together with the laboratory data integrity expectations for chromatographic data systems, including integration and reprocessing.

What inspectors look for

• Whether system suitability was run, met and documented before sample results were reported.
• Whether integration and reprocessing of chromatograms follow controlled procedures, and whether changes are justified and visible in audit trails.
• Whether any method adjustments stayed within the allowed limits and were documented.

Related regulations