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[nihal]

Hi,
I have been working at drug quality control laboratories.I m not experienced yet.Can you explain me that;
what means specified unidentified degradation product and what means unspecified degradation product?
If you answer me ı will be very happy.
Thank you for now.

[David Blais]

Hi Nihal,

specified unidentified degradation product = a peak in your chromatogram that is a known degradation product, but has yet to be identified (either by MS, NMR, IR, etc) and characterized

unspecified degradation product = a peak in your chromatogram that has not been seen before

At least, that's what I think you mean by your phrases.

-Dave

[Dan]

Hello nihal,

Dave has given good definitions. If you want more information, then check out the ICH which is the group that developed the definitions in its guidelines.

The ICH is the International Conference on Harmonisation:

http://www.ich.org/UrlGrpServer.jser?@_ ... MPLATE=254

The ICH guideline you want is Q3B(R):

http://www.ich.org/MediaServer.jser?@_ID=421&@_MODE=GLB

Regards,
Dan

[adam]

An interesting question. This is one of those issues that seems to go endlessly in circles.

Personally, I would define these terms differently. The ICH guidances on impurities specify a reporting limit (above which values should be reported) and an identification limit (above which an attempt should be made to identify the impurity).

By convention, a specification is generally set at or above the reporting limit (no sense setting a spec below the level at which the agency is interested).

So for impurities which are consistently observed above the reporting limit, but below the identification limit, we would have a specification (hence it is specified) but we would usually not know what it is (hence, it is unidentified). However, for impurity peaks that are not consistently observed above the reporting limit, we would generally not set a spec. So these would be unspecified impurities.


In summary

Specified: Means it has a specification.

Identified: Means we know what it is.

It is a common mistake (at least in my opinion) for people to define 'specified' as known, but I think that's incorrect.

I am curious to hear what others have to say on this topic.

Adam

[kiknos]

i myself is very interested in how to collect the unspecified/unidentified components(impurities) in certain crude pharmaceutical for identification?

LC/MS system can be very helpful, but some amount of those pure impurities may still need to be collected for characterization such as IR, NMR, etc. then how to get those impurities?

I just heard about something interesting:
use LC/MS to deduce what are the impurities(the molecule structures), then by organic synthesis to get some amount, then do the comparison.

your experiences?thanks!

kiknos in sunny but cold shanghai.