Topic summary

Adducts: sodium, potassium, and the peak you did not expect — does this still hold?

Analytics › Mass spectrometry high-resolution MS charge states mass error (ppm) MALDI-TOF counter-ion content Solved

This is a generated summary. It shows the 9 most-liked posts from a topic of 120, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

crossover_entryTL3Regular7 Jan 2026#4

Second this, and I would have said it less carefully.

29 likes 7mo

a.kwiatkowskiTL2Member Solution13 Jan 2026#8

Quantitation by MS: most quantitation is done by LC-UV detection at 214 nm, not by MS, because extinction coefficients are better known. MS can quantify if an internal standard is used but that requires preparation.

22 likes 6mo

k.haddadTL219 Jan 2026#12

Resolution and mass accuracy are different specifications. An instrument can resolve two species and still assign their masses imprecisely, and the reverse is also possible.

Not a conclusion. A place to stand while looking for one.

32 likes 6mo

c.tullochTL27 Feb 2026 · edited#30

The reason Adducts keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer is unknown.

28 likes 6mo

y.adebayoTL218 Feb 2026#41

Resolution: "high resolution" commonly means <5 ppm across the mass range. Unit-resolution instruments achieve ±1 Da at best and cannot distinguish two species differing by less than 1 Da in total mass.

32 likes 5mo

t.abubakarTL25 Mar 2026#58

Post #55 is right about the mechanism and I think understates the practical bit.

The question underneath Adducts is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.

Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.

31 likes 5mo

VPoulsenTL3Regular9 Mar 2026#62

Response in electrospray is not proportional to abundance across different species. Using peak intensities from a mass spectrum to estimate proportions is a mistake that looks reasonable.

29 likes 5mo

a.nascimentoTL29 Apr 2026#101

My experience of Adducts contradicts the reply above. I am posting it as a data point rather than as a refutation, because one person's experience is exactly that.

29 likes 4mo

bench_notesTL4 Moderator22 Apr 2026#118

Clear enough that I do not think I have a follow-up, which is unusual.

30 likes 3mo

Read the full topic (120 posts)

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Reading an MS report that only gives you a single number — the long versionAnalytics › Mass spectrometry · 2 replies

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