Probing the mechanisms of the self ion‐molecule reactions of dopamine in an ion trap mass spectrometer

Our previous work was the first to report [M+CH] + and [M+C 2 H 3 ] + ions in the self ion‐molecule reactions (SIMR) of two aza‐crown ethers in an ion trap mass spectrometer (ITMS). In this study, the CH and C 2 H 3 addition ions were also found in the SIMR of dopamine. The SIMR of dopamine lead to the formation of the protonated molecules ([M+H] + ), of adduct ions ([M+F] + , where F represents fragment ions), and of [M+CH] + , [M+C 2 H 3 ] + and [2M+H] + ions. Based on the combination of the results of isolation experiments and semi‐empirical calculations, the reactive site for the formation of the [M+H] + and [M+CH] + ions of dopamine is proposed to be the amino group. Copyright © 2003 John Wiley & Sons, Ltd.