Post #6 describes the usual case. This is about the unusual one.
Specificity: the method can distinguish the intended compound from related impurities and degradation products. Tested by comparing results on pure compounds, mixtures of compounds, and degraded samples.
I have changed my mind on this once already, so take it as current rather than settled.
Where I part company with post #46, and it is a narrow parting.
Validation is compound-specific and matrix-specific. A method validated for one peptide is a starting point for another and not a validated method for it.
I would treat that as a working assumption and revisit it.
Everything in post #60 holds. The case it does not cover is the one I have.
Something worth flagging about forced degradation studies: the strongest-sounding claims in this thread are the ones with no source attached, which is the usual pattern and not a coincidence.
A definition problem is doing most of the work in this forced degradation studies discussion. Once the term is pinned down I suspect the disagreement mostly goes away and what is left is small.
Why two laboratories may disagree: after validating the same method, they may still report different purity on the same sample due to integration differences, column age differences, subtle differences in mobile phase pH or temperature. This is normal and not a sign that one is wrong.
I am aware this is the third time this month I have made this point.
Post #93 describes the usual case. This is about the unusual one.
Forced degradation studies is well covered in the tag pages, and the older discussions are better than the recent ones because they were argued out properly. Worth twenty minutes before adding to this one.
Read the full topic (107 posts)
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Forced degradation studies: designing one that is informative — does this still hold?
The question in the title: Forced degradation studies: designing one that is informative — does this still hold? I will give what I have already checked below so nobody repeats it. The question about Forced…
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+37 | 41 | 1.2k | 12mo |
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An inter-laboratory comparison on one lot, tabulated — what changed since
An inter-laboratory comparison on one lot, tabulated — what changed since — setting out what I have, and where I think it stops being reliable. What changes if the standard account of inter-laboratory…
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+24 | 28 | 3.3k | 7mo |
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LOD and LOQ: definitions people get wrong
LOD and LOQ: definitions people get wrong — setting out what I have, and where I think it stops being reliable. What changes if the standard account of LOD and LOQ is wrong? I ask because I have been treating…
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2 | 43k | 8mo | |
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About the Method validation category
Specificity, linearity, precision, accuracy, robustness, system suitability, and why two labs disagree. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is…
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+1 | 5 | 468 | 5mo |
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Relative retention time as a better inter-laboratory comparator
On the subject in the title: Relative retention time as a better inter-laboratory comparator Working notes rather than a conclusion. What changes if the standard account of relative retention time is wrong? I…
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+7 | 11 | 28k | 14mo |
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Why one laboratory's 98.4% and another's 96.1% may not contradict
Why one laboratory's 98.4% and another's 96.1% may not contradict I have a specific reason for asking rather than idle curiosity, and the context is below. Posting the method first, because I know what the…
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+28 | 37 | 457 | 7mo |
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Robustness: the parameters worth deliberately varying
Robustness: the parameters worth deliberately varying Writing it up because I had to work it out twice and would rather nobody else did. A narrow question about robustness, deliberately narrow, because the…
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+53 | 57 | 664 | 8mo |
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Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on
Asking directly, because I could not find a straight answer: Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on Posting the method first, because I know what the first three…
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+10 | 14 | 13k | 5mo |
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Repeatability versus intermediate precision
Repeatability versus intermediate precision — setting out what I have, and where I think it stops being reliable. Trying to establish the boundary conditions on repeatability versus intermediate precision.…
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+119 | 134 | 34k | 13mo |
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Relative retention time as a better inter-laboratory comparator — does this still hold?
Relative retention time as a better inter-laboratory comparator — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. What changes if the standard…
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+11 | 15 | 21k | 21mo |