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c/hplc·submitted 6 months ago by u/yara_boateng

help me understand LC-MS, I have read the wiki twice

Labbranch of 8 comments

The title is the whole question — help me understand LC-MS, I have read the wiki twice — but here is why I am asking. 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. Reading a…

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8 comments, started 6 months ago
u/kofi_ferreira403 points·6 months ago

Gave the same trace to two people I trust and got two integrations about a point apart. That was the most educational afternoon I have had here.

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u/rosa_sandvik266 points·6 months ago

Yes — system suitability first. Without it the number is an assertion about the instrument, not the sample.

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u/georgi_chowdhury256 points·6 months ago

That is area percent, not mass percent. The trace cannot give you the second one.

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u/nora_lundgren177 points·6 months ago

Chased a ghost peak for three weeks. It was the plumbing. It is always the plumbing.

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u/gustav_solberg-31 points·6 months ago

A shoulder that does not baseline-resolve cannot be quantified honestly. You can report it as an unresolved shoulder, which is useful information, or you can develop the method until it resolves.

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u/amara_haddad1 point·6 months ago

A shoulder that does not baseline-resolve cannot be quantified honestly.

Disagreeing with this bit: that spread is ordinary inter-lab variance, not a disagreement about the material.

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u/cormac_roos1 point·6 months ago

That figure cannot be quoted to two decimals off that baseline. The precision is not in the data.

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u/first_hundred1 point·6 months ago

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

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