Method validation is the demonstration that a method can separate the compound from its degradation products and impurities reliably. A method that cannot resolve an impurity from the parent peak will not detect that impurity.
Adding the caveat now so it does not have to be extracted later.
Building on post #35 rather than restating it.
Retention time is only comparable within a laboratory on a given method. Quoting a retention time across two reports as evidence of identity is not a valid comparison.
Worth separating two things that post #60 runs together.
On Resolution and tailing factor: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.
A shoulder on the trailing edge is most often a closely related species rather than an artefact. The way to find out is to change the gradient slope, not to argue about the integration.
It took me longer than it should have to see that.
Purity by chromatography answers "what proportion of what I detected is the intended species". It does not answer how much is in the vial, which is a separate assay.
If this contradicts something upthread, the upthread version may well be the better one.
Injection volume matters because column overload distorts peak shape, and an overloaded main peak can swallow a small neighbour. A certificate without injection volume is missing something load-bearing.
This follows post #93 rather than contradicting it.
Small methodological point on Resolution and tailing factor: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.
Post #105 put the caveat in the right place and I want to underline it.
Answering the Resolution and tailing factor question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken.
Read the full topic (113 posts)
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Injection volume, overload, and peak distortion — one year on
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Revisiting: Theoretical plates: useful number or ritual?
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+16 | 21 | 1.2k | 1d |
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[2026 update] Detection wavelength and why 214 nm and 280 nm disagree
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+69 | 76 | 920 | 6h |
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Gradient steepness and apparent purity: a worked comparison
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2 | 51k | 22mo | |
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What a reversed-phase purity number actually is — the long version
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Carryover and the ghost peak from last week's standard
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+80 | 92 | 16k | 16mo |
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Blinding yourself: practical methods and their limits
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+40 | 44 | 33k | 5d |
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Revisiting: Sample size in a voluntary survey: the selection problem
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2 | 56k | 9mo | |
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