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Mass spectrometry

LC-MS and high-resolution MS, charge states, mass accuracy in ppm, and what identity confirmation does and does not establish.

30 topics1,626 posts12 solved Moderators: dr_okonkwo, owen.brady About this category

LC-MS high-resolution MS mass error (ppm) charge states MALDI-TOF counter-ion content

30 topics

Topic	Participants	Replies	Views	Activity
Charge states for a 4 kDa peptide, worked through high-resolution MS counter-ion content charge states LC-MS Solved On the subject in the title: Charge states for a 4 kDa peptide, worked through Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. retatrutide has a…	+124	146	15k	16mo
[2026 update] Charge states for a 4 kDa peptide, worked through counter-ion content MALDI-TOF high-resolution MS LC-MS On the subject in the title: Charge states for a 4 kDa peptide, worked through Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. semaglutide has a…	+116	135	31k	3mo
Distinguishing a deletion sequence by mass alone mass error (ppm) high-resolution MS LC-MS MALDI-TOF Solved Distinguishing a deletion sequence by mass alone 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.…	+121	129	25k	17mo
Reading an MS report that only gives you a single number 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
Counter-ion content and its effect on measured mass 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
High-resolution MS on aggregates and what it can see charge states counter-ion content high-resolution MS Posting this under the heading it deserves: High-resolution MS on aggregates and what it can see Everything below is what sits behind that. Working through the identity arithmetic and I would like it checked.…	+117	123	6.5k	8mo
Adducts: sodium, potassium, and the peak you did not expect — does this still hold? 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
Mass error in ppm: the arithmetic and the caveat 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
Distinguishing a deletion sequence by mass alone — the long version high-resolution MS mass error (ppm) charge states MALDI-TOF On the subject in the title: Distinguishing a deletion sequence by mass alone — the long version Working notes rather than a conclusion. I would like to understand what this number means before I repeat it…	+38	44	60k	11mo
Oxidation and deamidation mass shifts, tabulated counter-ion content charge states LC-MS mass error (ppm) Solved Posting this under the heading it deserves: Oxidation and deamidation mass shifts, tabulated Everything below is what sits behind that. Working through the identity arithmetic and I would like it checked.…	+67	76	21k	16mo
Why mass spectrometry cannot tell you about an epimer LC-MS mass error (ppm) high-resolution MS charge states Why mass spectrometry cannot tell you about an epimer I have a specific reason for asking rather than idle curiosity, and the context is below. Posting the method first, because I know what the first three…	+75	82	4k	17mo
Adducts: sodium, potassium, and the peak you did not expect LC-MS MALDI-TOF mass error (ppm) Wiki Adducts: sodium, potassium, and the peak you did not expect Writing it up because I had to work it out twice and would rather nobody else did. I would like to understand what this number means before I repeat…	+70	77	3.5k	15mo
High-resolution MS on aggregates and what it can see — one year on LC-MS counter-ion content MALDI-TOF charge states Solved High-resolution MS on aggregates and what it can see — one year on 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…	+54	58	1.2k	23mo
Second pass at: What a 2 ppm match establishes, and what it does not MALDI-TOF mass error (ppm) counter-ion content high-resolution MS Second pass at: What a 2 ppm match establishes, and what it does not — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked.…	+44	49	8.1k	1d
What a 2 ppm match establishes, and what it does not 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 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
Coming back to: Oxidation and deamidation mass shifts, tabulated LC-MS charge states MALDI-TOF high-resolution MS Oxidation and deamidation mass shifts, tabulated — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked. retatrutide has a…	+34	38	4.8k	10mo
Reading an MS report that only gives you a single number — the long version mass error (ppm) counter-ion content LC-MS high-resolution MS Reading an MS report that only gives you a single number — the long version — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I…		2	47k	18mo
Mass error in ppm: the arithmetic and the caveat — a second dataset 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
About the Mass spectrometry category LC-MS high-resolution MS mass error (ppm) Pinned Wiki LC-MS and high-resolution MS, charge states, mass accuracy in ppm, and what identity confirmation does and does not establish. This post is a community wiki: any member at trust level 3 or above can edit it,…	+5	9	19k	6h
Isotope patterns and why the monoisotopic peak is not the tallest LC-MS MALDI-TOF mass error (ppm) high-resolution MS Isotope patterns and why the monoisotopic peak is not the tallest — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked.…	+12	16	7.5k	17mo
Second pass at: Counter-ion content and its effect on measured mass 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
Second pass at: MALDI versus ESI for a quick identity check MALDI-TOF mass error (ppm) high-resolution MS counter-ion content Solved Second pass at: MALDI versus ESI for a quick identity check 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…		2	18k	7mo
Coming back to: Deconvolution of a multiply charged envelope counter-ion content charge states high-resolution MS On the subject in the title: Deconvolution of a multiply charged envelope Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. tirzepatide has a…		2	12k	22mo
Isotope patterns and why the monoisotopic peak is not the tallest — does this still hold? charge states counter-ion content high-resolution MS mass error (ppm) Solved Isotope patterns and why the monoisotopic peak is not the tallest — does this still hold? — that is the question, and I have not found it answered plainly anywhere I have looked. Working through the identity…		2	4.6k	7h
MS/MS sequence confirmation: what it costs and when it is worth it LC-MS MALDI-TOF charge states Solved Pinned MS/MS sequence confirmation: what it costs and when it is worth it — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it…	+2	6	2.7k	1d
MALDI versus ESI for a quick identity check high-resolution MS charge states mass error (ppm) MALDI-TOF Closed On the subject in the title: MALDI versus ESI for a quick identity check Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. tirzepatide has a…		2	2k	11mo
[2026 update] Why mass spectrometry cannot tell you about an epimer 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
Charge states for a 4 kDa peptide, worked through — the long version LC-MS high-resolution MS mass error (ppm) Charge states for a 4 kDa peptide, worked through — the long version 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…		2	293	3mo
Deconvolution of a multiply charged envelope 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

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