Adduct of 40.5Da

[fabienco]

I can see an adduct of 40.5Da on the molecule I am analysing.
Has anybody seen this before?
Thank you.

[HT]

41 Da is usually Acetonitrile.

[MG]

Can you distinguish the A+1 (carbon-13) peak for the adducted molecule? If so, is it 1m/z or 0.5m/z higher? This will tell you if that ion is doubly charged or not. The fact that you see the adduct as 40.5 makes it sound like it could be doubly charged.

[fabienco]

I can see the A+1 (C13), the adduct is related to the mean peak as I can see it when I select the mean peak in the ion trap for MS/MS experiment.