Analytics · Mass spectrometry

Coming back to: Deconvolution of a multiply charged envelope

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

v.rautioTL2 Moderator23 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.vermeulenTL2 Moderator26 Sep 2024#2

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

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

post #2 is right about the mechanism and I think understates the practical bit.

Charge states observed: for semaglutide (4113.6 Da) the doubly charged ion appears at m/z ≈ 2057, triply charged at ≈ 1371, quadruply at ≈ 1029. Those are the positions to look for; the heights depend on the ionization efficiency.

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.

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