Analytics · Mass spectrometry

Coming back to: Deconvolution of a multiply charged envelope

Analytics › Mass spectrometry counter-ion content charge states high-resolution MS

v.rautioTL223 Sep 2024#1

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 monoisotopic mass close to 4813.5 Da. On an electrospray instrument I would expect to see the multiply charged series rather than the intact singly charged ion, so for the doubly charged species I calculate (4813.5 + 2 x 1.00728) / 2, and for the triply charged the analogous expression.

The observed values in the report sit within a few ppm of those. My question is what that actually establishes, because I have seen people treat a mass match as a purity result and I do not think it is one.

6 likes 22mo

ca.vermeulenTL226 Sep 2024#2

The arithmetic for a doubly charged species is (M + 2 x 1.00728) / 2, and the analogous expression for higher charge states. Working it through once makes the reported values legible.

10 likes 22mo

endpoint_lineTL3Regular29 Sep 2024#3

v.rautio, post #1: 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 monoisotopic mass close to 4813.5 Da. On an electrospray instrument I would expect to see the multiply charged series rather than the… Go to post

Picking up post #2: that is the part I would want checked first.

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.

The general case is well covered; this is the awkward specific one.

22 likes in reply to #1 22mo

Promoted into the documentation commons. The content of this topic is maintained at LC-MS identity confirmation, with named maintainers and a review date. The promotion was discussed in doc review. Corrections are best raised against the document, which is the version that gets kept current.

Suggested topics

Topic	Participants	Replies	Views	Activity
High-resolution MS on aggregates and what it can see Analytics › Mass spectrometry 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. Something about high-resolution does not reconcile and I would like…	+117	123	6.5k	8mo
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. Something about Counter-ion content does not reconcile…		4	16k	4mo
Charge states for a 4 kDa peptide, worked through Analytics › Mass spectrometry 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
Isotope patterns and why the monoisotopic peak is not the tallest Analytics › Mass spectrometry 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. Isotope patterns: what I expected, what I found, and the gap between…	+12	16	7.5k	17mo
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? Adducts keeps being re-asked here and I think that is because…	+113	119	1.7k	3mo

Related topics — sharing the tags counter-ion content, charge states, high-resolution MS

Topic	Participants	Replies	Views	Activity
Coming back to: Oxidation pathways for methionine and tryptophan Analytics › Impurities & related substances HPLC counter-ion content water content data table Oxidation pathways for methionine and tryptophan Writing it up because I had to work it out twice and would rather nobody else did. Reading back through what has been written here about Oxidation pathways for…	+1	5	36k	15mo
Lyophilisation and why the cake looks the way it does Pharmacology › Formulation chemistry sterile water bacteriostatic water storage cloudy or discoloured solution Posting this under the heading it deserves: Lyophilisation and why the cake looks the way it does Everything below is what sits behind that. I was wrong about lyophilisation in a thread last spring and I…	+33	37	60k	6mo
About the Impurities & related substances category Analytics › Impurities & related substances forced degradation counter-ion content water content Pinned Wiki Deletion sequences, oxidation, deamidation, aggregates, residual solvents, and counter-ion content. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is recorded…	+6	10	50k	15h
Revisiting: Aggregates and why a purity assay may miss them entirely Analytics › Impurities & related substances endotoxin testing HPLC counter-ion content water content Solved Posting this under the heading it deserves: Revisiting: Aggregates and why a purity assay may miss them entirely Everything below is what sits behind that. I would like to disagree carefully with the settled…	+48	53	918	8mo
Isotonicity and what happens when you get it wrong Pharmacology › Formulation chemistry sterile water counter-ion content storage On the subject in the title: Isotonicity and what happens when you get it wrong Working notes rather than a conclusion. I was wrong about isotonicity in a thread last spring and I would like to correct it…	+27	31	11k	18mo

Sponsored PeptideMeter — peptide analytics and supplier verificationPurity analysis and structured supplier verification, published as dated records rather than scores. Referenced throughout our sourcing documentation.View analytics →