Datensatz

Zusammenfassung

Gas-phase reactions of temporally
stored ions play a significant role in trapped ion
mass spectrometry. Especially highly labile ion
species generated through electron ionization
(EI) are prone to undergo gas-phase reactions
after relaxation to a low vibrational state. Here,
we show that in the C-Trap of the Q Exactive GC
Orbitrap mass spectrometer, gaseous water reacts
with radical cations of various compound
classes. High-resolution accurate mass spectrometry
of the resulting ions provides a key to the mechanistic understanding of the chemistry of high energetic
species generated during EI. We systematically addressed water adduct formation by use of H2O and D2
18O in
the C-Trap. Mass spectra of halogen cyanides XCN (X=Cl, Br, I) showed the formation of HXCN+ species,
indicating hydrogen atomic transfer reactions. Relative ratios of HXCN+/XCN+• increased as the electronegativity
of the halide increased. The common internal calibrant perfluorotributylamine forms oxygenated products from
water reactive fragment ions. These can be explained by the addition of water to an initial cation followed by
elimination of two HFmolecules. This addition/elimination chemistry can also explain [M+2]+ and [M+3]+ ions that
commonly occur in mass spectra of silylated analytes. High-resolution accurate mass spectra of trimethylsilyl
(TMS) derivatives revealed these as [M−CH3
•+H2O]+ and [M−CH4+H2O]•+, respectively. This study explains
common fragment ions in ion trap mass spectrometry. It also opens up perspectives for the systematic
mechanistic and kinetic investigation of high-energy ion reactivity.