By Anonymous on Friday, April 2, 2004 - 02:50 am:
Dear All,
We are using PE-SCIEX API 3000 (Tripe quadrapole) LC/MS/MS instrument. Is it possible to get the elemental composition from this Triple quadrapole instrument?
For the determination of Elemental composition of the Molecular ion, Any of the analyser will work?
Advance thanks
By MG on Friday, April 2, 2004 - 09:24 am:
If you mean exact mass, no. You need a TOF, sector, or FT-ICR for that kind of resolution and accuracy.
You can however make inferences about the presence or absence of certain elements based on the isotope distribution of, and mass of the molecular ion. For example, maximum # of carbons, even / odd number of nitrogens, number of chlorines, bromines, sulfur, etc. See "Interpretation of Mass Spectra" by McLafferty, or search the web. The fragmentation rules in that book apply mainly to EI, but the isotope rules apply equally to LC/MS (but keep in mind that the nitrogen rule is reversed for LC/MS).
By Anonymous on Sunday, April 4, 2004 - 11:38 pm:
Dear MG,
With reference to the adduct formation in LCMS, is there any possibility of CH3OH adducts???
Is there any possibility of getting these type of
adducts [M+ H+ CH3OH] and [M+Na+CH3OH]?
Advance thanks
By MG on Monday, April 5, 2004 - 09:09 am:
Yes, I've seen ions before that would correspond to these sort of adducts with methanol. They are not usually the major peaks. To reduce or eliminate adducts, increase your up-front CID voltage (fragmentor, declustering potential, etc.).