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

On post #2 — agreed on the reasoning, with one qualification.

Desalting before analysis: some samples need desalting to remove salts that suppress the peptide signal. Report whether desalting was used, because it can affect the apparent ionization efficiency and the reported purity.

29 likes 7mo

a.kwiatkowskiTL2Member Solution13 Jan 2026#8

Common adducts: sodium adds ≈22, potassium adds ≈38 compared to hydrogen. A [M+Na]+ peak is common and its mass is predictable from the base mass.

22 likes 6mo

k.haddadTL2 Moderator19 Jan 2026#12

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.

32 likes 6mo

c.tullochTL2 Moderator7 Feb 2026 · edited#30

Sample matrix effects: if a sample is dissolved in a complex matrix, other compounds in the matrix can suppress the peptide signal. Clean samples give higher sensitivity than dirty samples.

28 likes 6mo

y.adebayoTL2 Moderator18 Feb 2026#41

Purity and identity are different questions: LC-MS establishes that the species at a retention time has the expected mass. It does not establish how much of the sample is that species (that is what LC-UV purity answers).

32 likes 5mo

t.abubakarTL2 Moderator5 Mar 2026#58

Picking up post #55: that is the part I would want checked first.

31 likes 5mo

VPoulsenTL3Regular9 Mar 2026#62

Electrospray ionisation produces multiply charged ions. For a 4 kDa peptide you expect mostly 2+, 3+, and 4+ charge states. Reading an electrospray spectrum means recognizing the envelope, not looking for one peak.

29 likes 5mo

a.nascimentoTL2 Moderator9 Apr 2026#101

29 likes 4mo

bench_notesTL4 Moderator22 Apr 2026#118

Staff post. Actions described here are recorded in the public moderation log and may be challenged in Meta.

Coming back to post #116, because the follow-up matters more than the original answer.

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

30 likes 3mo

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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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