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Is it normal practice not to perform an LOD for a GC related substances method validation. If so, how can this be justified to a regulatory agency.
Hi
The short version is that ICH Q2 R1 and FDA draft on method validation from 2000 both indicate that it "may be needed in some cases". Quite vague, and in my experiance most validation I have seen/done for quatification of related substances includes some LOD investigation and most authorities seems to expect some discussion around it (I also get LOD questions on new monographs in pharmacopieas sometimes).
A longer version.
If your validation includes particular toxic impurities and specification limits below the normal ones, then I would strongly recommend that you go for LOD and spend some time on it.
If you work against the "normal" report limits as per ICH Q3a (APIs)(0,03/0,05%) then I think an "estimated" LOD would be sufficient by making a dilution from LOQ and estimate LOD.
Unless you have response issues, working against the ICH report limits is normally not a big problem .
The above is based on the assumption that signal to noise ratio is used for LOD/LOQ. I know there has been a huge debate around what tool to use.
Hope it helped a bit and do not forget to include relevant chromatograms for LOQ/LOD (as per ICH Q2).
Anyone with experiance where pharma authoriyties have accepted exclusion of LOD?
