Tandem mass spectrometry experiments based on diagnostic gas-phase ion-molecule reactions provide a reliable tool for the identification of specific functionalities in unknown compounds in mixtures. Most of these reactions have been examined with low-resolution mass spectrometers, such as triple quadrupoles and linear quadrupole ion traps, which cannot be used to determine the elemental compositions of ions. In order to collect high-resolution data for ion-molecule reactions, a high-resolution mass spectrometer—a quadrupole/orbitrap/linear quadrupole ion trap tribrid instrument—was modified in this study by introducing a portable reagent inlet device that has been described previously. The analyte ions were isolated in the linear quadrupole ion trap of the mass spectrometer. They were then transferred into the high-pressure cell that was selected as the reaction chamber as the neutral reagent carrier gas (helium) directly entered this area. Examining a previously studied reaction—the reaction of protonated 1,1'-sufonyldiimizadole with 2-methoxypropene—showed that the modified tribrid mass spectrometer can be used to study ion-molecule reactions. In order to explore the high-resolution capabilities of the instrument, two isomeric ions and one ion that was an isobar relative to the other two, protonated glycylalanine, glutamine, and lysine, were allowed to react with diethylmethoxyborane. These data demonstrated the formation of different product ions for the three ions. In different experiments, diagnostic ion-molecule reactions were used to determine the structures of the fragment ions formed upon collision-induced dissociation of protonated glycylalanine and protonated glutamine. This experiment presents a promising new tool for the elucidation of the structures of fragment ions in mass spectrometry.

Modification of a quadrupole/orbitrap/linear quadrupole ion trap tribrid mass spectrometer for diagnostic gas-phase ion-molecule reactions

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