For example, I have a system suitability injection to determine the resolution between a main peak and an impurity, where I'm getting a resolution of More than 3.
But when I inject a sample solution, I can not apply resolution (i.e. no clear resolution) between both the peaks, as the impurity peak is eluting as a Rider peak.
Note: In system suitability solution known concentration of impurity is being spiked along with the main component.
Please suggest me whether it is acceptable?
Yes per USP you are demonstrating that your instrument is capable of this baseline separation. However, your chromatography (method) is NOT suitable since the sample is not matrix matched to your standard.
The solution may be as simple as diluting the sample 1/10 in mobile phase and injecting 10X the injection volume (20 uL to 200 uL). Your standard should be similarly diluted.
The system suitability is there to establish that your chromatography system is capable of performing analysis to the required standrad you require for successful analysis so I would say , yes. Is the main/impurity peak significantly larger than that shown in the System Suit peak? Perhaps excipient in your sample is causing peak broadening? If you have the flexibility to redevelop the method some more I would do so..
If you are getting good intraday and intraday accuracy...and precision...than you can go ahead
It will depend on how your system suitability test and your SOP is being set up.
The SST is a simple procedure to automatically check if the instrument and separation is still performing according to its initial definition. Usually a defined mixture, well known sample, or "check standard" is used for the SST.
Then we have the separation and analysis of real world samples. In case their composition, concentrations, concentration rations as severely different from the system suitability test, the SST conditions might not be fulfilled. If, however, the conditions being set for a successful analysis of your sample is fulfilled, you could go ahead. For your example this is not the case.
In many laboratories I saw that the SST do not only check for the general performance of the instrument, but also for the separation capabilities of the column. Many of our colleagues use a solution being quite close to how their samples are, so that they have a good grip on what's going on in terms of column aging etc.
If, as suggested by our colleagues above, the sample composition is too different and a dilution does not solve the issue, it might be time to rethink the method applied. Would a new column help? Different batch / source of organic modifier...
I cross the fingers that the solution in your case is as simple as a dilution or a smaller injection volume... Working in a validated environment (what I assume from your message) and changing an existed and validated method is a gigantic work...
Then to your situation: Integrating rider peaks is a science of itself. Can be easy, but also a nightmare. It will depend on the relative sizes of main-peak to rider. If the rider get small and smaller it will become very delicate to perform a meaningful peak area integration. Believe it or not: In such situations a lifesaver for us was peak height integration. And allow me to state the obvious: Baseline separation or slightly overlapping peaks (R > 1.3) would be much more reliable, than Rider integration. If possible, I would dilute, try working on the separation, use a different column selectivity, carbon load etc, if the SOP provides such changes.
Hope this helps.
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