Reactions of Ions from Pyrolyzed Cellulose with Adventitious Water in a Quadrupole Ion Trap

摘要

We investigated the adduction of water with protonated levoglucosan in a 3D quadrupole ion trap, an uncommon and thus characteristic reaction. This reaction is a pseudo-first order reaction that only depends on the concentration of levoglucosan; water is in excess. To determine the source of the water in the ion trap, the composition of the EESI solvent was changed. Removing water from the EESI solvent prevented the water adduct, suggesting that the water in the ion trap may be coming from the EESI solvent. However, replacing H_2O with D_2O in the EESI solvent did not lead to the production of a D_2O adduct with protonated levoglucosan, indicating that the source of water is not from the EESI solvent. Water is instead present as a background neutral in the vacuum system. Because only a fraction of the ions of m/z 163 produced by EESI of volatilized levoglucosan with 50/49/1 methanol/D_2O/acetic acid react with water, it may be concluded that two different ion structures of m/z 163 are present in the ion trap. In addition, using an EESI solvent containing H_2O in the EESI solvents had a relative reaction rate 50% faster than the solvent containing D_2O, suggesting the reactive ion structures are not the same. The non-reactive structures produced from the ionization of levoglucosan with methanol/D_2O or acetonitrile as the EESI solvent may or may not be the same; suggesting at least 3 ion structures observed for protonated levoglucosan, depending on the solvent.