Abstract: An elcctrobiochemical system for the determination of the presence and optionally concentration of an analyte in a liquid medium, the system comprising an electrode having immobilized thereon a member of a recognition pair, the other member of said pair being said analyte, the presence of said analyte in the medium resulting in formation of a pair complex, being a complex between said immobilized member and said analyte; the system further comprising redox molecules capable of changing their redox state by accepting electrons from or donating electrons to the electrode; the formation of the pair complex on the electrode bringing a change in the electrical response of the system, whereby the presence and optionally the concentration of said analyte in the medium can be determined.

Abstract: 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.