Chromatography Forum

Hi all,
The System suitability test when we determine the related substances in a drug according to pharmacopoeia is usually resolution check. As long as a resolution of API peak and an impurity peak is higher 1.5 for example, we can run the sequence.
But how do we know that the system is stable or not without injecting a set of samples?
How about your lab?
Thank you!

Are you assessing any sort of repeatability along with your resolution solution? Generally in the past for related substances methods I have worked on, you would have the following:

-sensitivity solution
-resolution solution
-working standards x5 or x6 to assess repeatability
-bracketing standards throughout the run

However that's just a very generic example. I would definitely assess %RSD of peak areas or responses of working standards. Depending on the level your working standards are at, the requirements for %RSD are generally not as tight as those for an assay.

You should be able to assess system suitability prior to injecting any samples.

^or be thoroughly prepared to disregard all data collected after a failing SST result. Consult your SOPs.