Topic summary

About the Mass spectrometry category

Analytics › Mass spectrometry LC-MS high-resolution MS mass error (ppm) Pinned Wiki

This is a generated summary. It shows the 5 most-liked posts from a topic of 10, 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.

l.dialloTL2 Moderator13 Jun 2026#3

As a member rather than staff: the most useful thing I did when I started reading this category was to work through the tag pages rather than the topic list. The topic list shows you what is recent. The tags show you what is settled.

23 likes 1mo

b.demirTL2 Moderator20 Jun 2026#4

Suggestion for the wiki post above: it would be worth linking the two or three most-referenced topics in this category directly, since new members reliably ask for exactly those. Happy to make the edit myself if nobody objects, with a revision note.

10 likes 1mo

m.duarteTL2 Moderator10 Jul 2026 · edited#7

Worth separating two things that post #3 runs together.

What mass accuracy establishes: the measured mass is consistent with a specific composition. What it does not establish: purity, sequence order, stereochemistry, or the absence of an isobaric species. Every one of those requires something else.

31 likes 18d

l.aguirreTL2 Moderator16 Jul 2026#8

post #7 is right about the mechanism and I think understates the practical bit.

Mass accuracy is expressed in parts per million. It is the difference between observed and theoretical mass divided by theoretical mass, multiplied by a million. A high-resolution instrument in good calibration achieves low single-digit ppm on a peptide of this size.

16 likes 12d

ar.petrovTL2 Moderator28 Jul 2026#10

Picking up post #7: that is the part I would want checked first.

Tandem mass spectrometry: MS/MS fragments the molecular ion and uses fragment masses to confirm identity and detect modifications. A simple identity confirmation by LC-MS does not address post-translational modifications or impurities with the same or very close mass.

24 likes 6h

Read the full topic (10 posts)

Suggested topics

Topic	Participants	Replies	Views	Activity
Mass error in ppm: the arithmetic and the caveat Analytics › Mass spectrometry LC-MS high-resolution MS MALDI-TOF counter-ion content Solved Mass error in ppm: the arithmetic and the caveat Writing it up because I had to work it out twice and would rather nobody else did. Working through the identity arithmetic and I would like it checked.…	+108	125	1.5k	5mo
Mass error in ppm: the arithmetic and the caveat — a second dataset Analytics › Mass spectrometry counter-ion content mass error (ppm) charge states LC-MS Solved On the subject in the title: Mass error in ppm: the arithmetic and the caveat — a second dataset Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…	+20	24	1.7k	1d
Second pass at: Counter-ion content and its effect on measured mass Analytics › Mass spectrometry mass error (ppm) counter-ion content MALDI-TOF charge states Solved Second pass at: Counter-ion content and its effect on measured mass Writing it up because I had to work it out twice and would rather nobody else did. Working through the identity arithmetic and I would like…		4	16k	4mo
What a 2 ppm match establishes, and what it does not Analytics › Mass spectrometry high-resolution MS charge states LC-MS MALDI-TOF What a 2 ppm match establishes, and what it does not — that is the question, and I have not found it answered plainly anywhere I have looked. Working through the identity arithmetic and I would like it…	+56	60	5.2k	9mo
MS/MS sequence confirmation: what it costs and when it is worth it — what changed since Analytics › Mass spectrometry charge states LC-MS MALDI-TOF counter-ion content Closed Posting this under the heading it deserves: MS/MS sequence confirmation: what it costs and when it is worth it — what changed since Everything below is what sits behind that. Working through the identity…	+34	39	21k	1mo

Related topics — sharing the tags LC-MS, high-resolution MS, mass error (ppm)

Topic	Participants	Replies	Views	Activity
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 Solved Asking directly, because I could not find a straight answer: Adducts: sodium, potassium, and the peak you did not expect — does this still hold? Posting the method first, because I know what the first three…	+113	119	1.7k	3mo
Deconvolution of a multiply charged envelope Analytics › Mass spectrometry MALDI-TOF charge states mass error (ppm) counter-ion content Closed Deconvolution of a multiply charged envelope — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked. tirzepatide has a…		2	63	10mo
Counter-ion content and its effect on measured mass Analytics › Mass spectrometry high-resolution MS charge states MALDI-TOF LC-MS Solved On the subject in the title: Counter-ion content and its effect on measured mass Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. retatrutide has a…	+100	108	45k	12mo
Reading an MS report that only gives you a single number Analytics › Mass spectrometry counter-ion content mass error (ppm) charge states On the subject in the title: Reading an MS report that only gives you a single number Working notes rather than a conclusion. I would like to understand what this number means before I repeat it anywhere. A…	+100	113	48k	13mo
[2026 update] Why mass spectrometry cannot tell you about an epimer Analytics › Mass spectrometry high-resolution MS counter-ion content MALDI-TOF Why mass spectrometry cannot tell you about an epimer — that is the question, and I have not found it answered plainly anywhere I have looked. Working through the identity arithmetic and I would like it…		2	1k	8mo