An analytical method for determining the presence or concentration of an analyte in a liquid medium is provided in which electrons are transferred from an electrode material of an electrode to the redox center of an enzyme, by the mediation of an electron mediator, whereby in the presence of an analyte the enzyme calalyzed a redox reaction in which the analyte is converted into a product. By measuring either the concentration or the product or the charge which flows in this process, the presence and/or concentration of the analyte in the medium is determined. Either or both of the enzyme and the electron mediator are immobilized on the electrode.