Revisiting: Why I ask for the gradient before I discuss the number
System suitability testing: injections run before and during the sample run to establish whether the instrument, column and method were performing when the sample was analysed. If suitability did not pass, the sample results from that run are uninterpretable.
A single observation, in a thread that deserves better than single observations.
Everything in post #6 holds. The case it does not cover is the one I have.
Change the wavelength and the proportions change even though the sample has not. That is the reason the wavelength has to be on the document for the number to mean anything.
I would be glad to be shown a cleaner way of putting this.
Post #13 answers the question as asked. The question underneath it is different.
Peaks that do not elute do not appear in the area percentage. Aggregates and strongly retained species can be entirely invisible to a standard method, which is a ceiling on what any purity figure can claim.
I would put a moderate confidence on that and no more.
If two laboratories disagree by more than two or three percentage points, work through method, integration, sample handling, whether it was the same lot and the same vial, and whether suitability passed. After all five, a gap needs an explanation.
Anyone with a larger sample, please post it.
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