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c/hplc·submitted 1 year ago by u/ewan_zielinski

[Question] chromatogram — what am I missing here

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Question in the title, detail here: chromatogram — what am I missing here. Area percent is the integrated area of your peak over the total integrated area at one wavelength on one gradient. Change any of those and the number changes without the sample changing. System suitability — repeat injections, tailing factor,…

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7 comments, started 1 year ago
u/ignacio_vanhecke138 points·1 year ago

Mass spectrometry answers identity. UV purity answers relative quantity under the run conditions. A document with one and not the other is answering half the question, and the half it answers should be stated.

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u/nora_lundgren68 points·1 year ago

Carryover from a previous high-concentration injection looks exactly like a small impurity. The blank injection is four minutes and it removes the ambiguity entirely.

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u/medutest_mel0 points·1 year ago

Carryover from a previous high-concentration injection looks exactly like a small impurity.

nora_lundgren is right — the integration choice is a decision and it should be stated alongside the result.

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u/hamza_weiss1 point·1 year ago

Cosigning the wavelength point. Half the disagreements in this board are two people looking at different detectors.

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u/anya_erdogan23 points·1 year ago

Careful — you are treating retention time as identity. Two things can co-elute and the trace will not tell you.

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u/ewan_zielinski38 points·1 year ago

Mass spectrometry answers identity.

Adding one practical thing — run the blank. It answers this before anyone has to argue about it.

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u/andres_restrepo32 points·1 year ago

Ran a blank after a high-concentration injection and found the carryover I had been calling an impurity.

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