Chromatography Forum

Thank you all for your comments. I do not really understand the need to determine impurities in an assay method when you already are determining impurities in an impurity method. The concentration of API in the impurity method is much greater then in the assay in order to be able to see impurities. I may not even detect the same impurities in my assay method due to concentration (roughly 1 / 10 as concentrated).

If you can’t detect some impurities or/and degradation products in your assay, so be it.
The point here is specificity and in the context of the assay it means that you - as far as possible – should separate the API (the mail peak) from the rest, so that the result is based only on the active substance. So, you should see it the other way around – if you can’t detect something it doesn’t count.
On the other hand, if it is detectable, then it should be separated. Not necessarily quantitated, because it’s the role of the purity method of analysis.

Hope the above clarifies my point.

Best Regards

Thanks danko, I can see your point.