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Precursor isotopes for negative ions appearing as M+1 and M+2

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Precursor isotopes for negative ions appearing as M+1 and M+2 Susan Abbatiello  2026-02-26 09:24
 

Hi!
I'm trying to generate a Skyline doc for PFAS in negative mode for 3 isotopes per precursor. The M-H mass is fine, but the second and third isotope masses shown are M+1 and M+2.

I have negative adducts specified in my settings. please help!
thanks,
sue
 
 
Brian Pratt responded:  2026-02-26 09:34

Hi Sue,

It's just an unfortunate collision of nomenclatures - those aren't charges, those are isotopes. If you look at the masses I believe you'll see they are correct.

Best regards,

Brian Pratt