Purity testing - distorted peak

[marina1111]

Hello everyone!
When I am running purity test of a basic compound I get a large tailing (4 and more). The tailing is only for this overloading quantity (for assay quantity the peak is symmetrical). Is this allowed? (I work with acidic pH and ion pairing agent). Also I will be glad to know in general if there are rulls for main peak in purity test.
Thank you!

[philippem]

Hi marina 1111,

Since you are overloading your column " normal" rules for chromatography do not count anymore.

Your objective is to determine the impurities. As long as your impurities are well separated from the mainpeak there is no problem,
Therefor it is advised (or agreable ) that the impurities elute before the mainpeak,so tailing of this mainpeak does not interfere with your impurities. This is however not always possible....
To achieve this, can be part of method development

regards

pHilippe

[marina1111]

Thank you for the unswer. Are those peak distortions also alowed in pharmaceutical analysis?

[philippem]

I would not accept those distortions during assay analysis. While doing method development for your analysis one should specifiy acceptance criteria and good chromatography should be challenged. those criteria are part of your ( validated) method.

pHilippe

[danko]

Hi Marina,

Philippe is absolutely right, as long as the method utilizes standards for the quantitation of these impurities.
But if you perform area % calculation i.e. the result is calculated as a ratio to the main peak area, than it is not acceptable to overload the latter either. The least you could do in this situation is to verify that impurity results are the same both with overloaded and with symmetrical main peak. But I’m not sure it’s quite possible.


Best Regards

[marina1111]

Thank you very much