Observation of self-ion-molecule reactions during collisionally activated dissociation in an ion-trap mass spectrometer

This paper describes the formation of protonated molecules (M + H]+) and adduct ions by self-ion-molecule reactions (SIMR) during collisionally activated decomposition (CAD) of methyne addition ions (M + CH]+) produced from chemical ionization (CI) or SIMR in both an external and internal source ion-trap mass spectrometer (ITMS). The CAD results for the methyne addition ions of dopamine produced from both SIMR and dimethyl ether CI undertaken in the external and internal source ITMS were compared in order to prove the occurrence of SIMR during CAD processes. Compared with the external source ITMS, the internal source ITMS is much more easily applicable to this type of reaction owing to the large population of neutral analytes present in the trap.