Before anything else: what was the gradient, and at what wavelength? Area percent at different wavelengths is not the same number even on the same sample because different species absorb differently at different wavelengths. With the method stated, I can tell you something useful. Without it, all I can say is that there is one large peak.
This follows post #6 rather than contradicting it.
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.
The number is defensible. The precision I gave it is not.
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.
Post #15 and I disagree about the size of the effect, not about the direction.
Reporting rather than recommending, on Theoretical plates. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
Read the full topic (22 posts)
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What a reversed-phase purity number actually is
The question in the title: What a reversed-phase purity number actually is I will give what I have already checked below so nobody repeats it. I would like to understand what this number means before I repeat…
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+87 | 101 | 27k | 4h |
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[2026 update] Detection wavelength and why 214 nm and 280 nm disagree
Detection wavelength and why 214 nm and 280 nm disagree — setting out what I have, and where I think it stops being reliable. I would like to disagree carefully with the settled view on Detection wavelength,…
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+69 | 76 | 920 | 6h |
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Why 99.2% and 97.8% on the same lot can both be correct
Why 99.2% and 97.8% on the same lot can both be correct I have a specific reason for asking rather than idle curiosity, and the context is below. I would like to understand what this number means before I…
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+16 | 20 | 3.1k | 11h |
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System suitability injections: if they failed, the run did not happen
Posting this under the heading it deserves: System suitability injections: if they failed, the run did not happen Everything below is what sits behind that. Proposing that system suitability injections…
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+23 | 27 | 6k | 11mo |
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About the HPLC & UHPLC category
Reversed-phase separations, gradients, columns, integration, and reading a chromatogram properly. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is recorded…
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4 | 137 | 18h |
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Repeatability versus intermediate precision — what changed since
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4 | 21k | 5h | |
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Seven-day rolling means and why weekly readings mislead
Seven-day rolling means and why weekly readings mislead Writing it up because I had to work it out twice and would rather nobody else did. Posting a series rather than a conclusion, with the method first.…
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+109 | 125 | 42k | 10h |
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Blinding yourself: practical methods and their limits — the long version
Blinding yourself: practical methods and their limits — the long version Writing it up because I had to work it out twice and would rather nobody else did. A narrow question about Blinding yourself,…
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+7 | 11 | 1.8k | 22h |
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Coming back to: Specificity, linearity, accuracy, precision, range, robustness — with real criteria
On the subject in the title: Specificity, linearity, accuracy, precision, range, robustness — with real criteria Working notes rather than a conclusion. Trying to establish the boundary conditions on…
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+93 | 99 | 1.4k | 6d |
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Cleaning a self-reported dataset and what you throw away — what changed since
Posting this under the heading it deserves: Cleaning a self-reported dataset and what you throw away — what changed since Everything below is what sits behind that. What changes if the standard account of…
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2 | 2k | 1h |