We describe formation and detection of transient radical intermediates and 2e , 2H(+) oxidation products (OPs) of dopamine (DA) by electrospray ionization (ESI) mass spectrometry (MS) which has not been reported previously. The results confirm formation of DA radicals by proton coupled electron transfer pathway. DA radicals and 2e , 2H(+) oxidation products that were identified are of interest because of their reported neurotoxicity. Using different solution compositions and MS detection conditions three different DA radicals were identified that have different stability. DA reactions with reactive oxygen species (ROS) relevant to DA reactivity in vivo are discussed. Detection of DA OPs by electrochemistry/mass spectrometry with a floated on-line electrochemical cell is also illustrated. (C) 2017 Published by Elsevier Ltd.