It is known that undiluted methanol can give mass transport-controlled steady-state oxidation currents at Pt microelectrodes. In the present study, the steady-state currents were examined under flow injection conditions. It was found that the methanol oxidation current, measured at a microelectrode electrochemical detector and at a fixed potential, decreased in the presence of electroinactive compounds, increased on the injection of methanol samples containing water and either increased or decreased when the ionic strength of the samples was changed. The results are promising in terms of future analytical applications, including indirect detection of electroinactive compounds.