Chromatography Forum

Hello all,
Someone asked as to extend runtime three times of mean peak for the assay of validation butches.
Injections concerned: blank, one inj of standard and one sample inj.
are there any guidance regarding this.
in the practice, we do that for related substances test, for all injections (even for system suitability in isocratic mode)
I would like to know more about run times duration, how and where.
thank you.

I'm not aware of any specific recommendation, but common sense suggests that going out to about 20 x the dead time should be sufficient. That's a k' value of 19. Other things being equal, peak height is proportional to 1/(1+k'), so by the time you're out that far, any trace peaks will be essentially indistinguishable from the baseline.

Additional note - if the method has been validated, presumably forced degradation samples have already had similar treatment done on them. If there were no late eluters then, you have no reason to suspect that the validation batches would be harboring any. On to the PQRI samples!

Thank you for the answer, it's what I suggested.(about the validated methode).