Chromatography Forum

Im quantifying a peak for assay and the current developed method we have., has a small degradant on the tail of the peak causing the peak purity to fail!!...is there any way i can justify this , thus allowing me to continue using this method

If your software can integrate the contaminant as a skimmed peak then you might be able to justify it.

"is there any way i can justify this , thus allowing me to continue using this method" - sure you can, just show how much impurity can be present, that is not causing assay results to be different

If the peak has an impurity peak on its tail it IS NOT pure. It is simply not separated. And if it is not pure and not separated there is no sense in using peak purity.

If the impurity was on the far tail and you could convince your integrator to make a valley-to-valley integration the peak might turn out pure.
What do you do in assay? Do you intergrate with the impurity peak?

Your question worries me a little. The method was setup to check peak purity for a reason... and the reason was just triggered. As already stated you really have to separate it so the integration does not include it in the main peak. in this scenario it may be that your peak purity settings are a bit too sensitive and you need to reset the threshold (noise reject) value.
Always remember that in UV peak purity you can never be sure of purity (co-eluant may have spectrum very close in appearance to main peak). Impurity detection can be fooled by noise at front and tail of peak. only the right settings allow you to be sure of impurity co-eluant. It's a bit of a subjective art at the best of times.

Can you do peak purity by MS instead? Much more valuable in my experience than doing so by DAD.