Electrooxidation of cytosine on bare screen-printed carbon electrodes studied by online electrochemistry-capillary electrophoresis-mass spectrometry

The electrooxidation of cytosine on common commercially available screen-printed carbon electrodes was investigated. To characterize the processes on the electrode surface, the oxidation products were analyzed by online electrochemistry-capillary electrophoresis-mass spectrometry. Capillary electrophoresis was the ideal separation technique as all occurring species were positively charged at acidic separation conditions. Comparing the results to literature data on cytosine oxidation by one electron oxidants, the compound 6-hydroxy-5-hydroperoxy-5,6-dihydrocytosine was identified as the main oxidation product that could be detected on the screen-printed carbon electrode material. This product species was found to be quite stable over an investigated period of 60 min under the conditions present in our experiments. A small amount of cytosine glycol was detected, probably formed as a decomposition product. During oxidation in acetate electrolyte, a side reaction with the electrolyte took place forming an artificial product, which was not the case in hydrogencarbonate electrolyte. This showed that products have to be investigated carefully in the context of the background electrolyte to avoid misinterpretations.