[Question] how do you actually verify LC-MS
how do you actually verify LC-MS — that is what I am asking, and I have already read the wiki twice. Reading a trace posted here, in the order I actually look at things. Axes first — if the wavelength and the time axis are not labelled, I stop. Then the baseline: where has it been drawn, and does the drawing absorb…
214nm sees the peptide bond, 280nm sees the aromatics
Started reporting my own integrations with the baseline choice stated. Arguments in my threads dropped by about half.
Sent the same vial to Janoshik and VendorInvestigate. 99.1% against a claimed 99.0%. The difference was the gradient, not the material.
That is area percent, not mass percent. The trace cannot give you the second one.
you cannot report to two decimals off that baseline
Small fix — 214nm, not 210. It matters for the comparison you are making with the other run.
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.
a shoulder is not an impurity until you can resolve it
Yes. Retention time is a hypothesis about identity. Mass is the answer.
Can you post the trace with the axes labelled?
system suitability before you believe any number on the run
Yes.
Disagreeing with this bit: that spread is ordinary inter-lab variance, not a disagreement about the material.
reproducibility beats resolution if you only get one of them
a blank injection between samples costs four minutes and settles most arguments
This. A shoulder that does not baseline-resolve is a question, not a quantity.
ghost peak, check the plumbing first, it is always the plumbing