Abstract: The subject matter of the invention is a method for the electrochemical determination of an analyte in the presence of an oxidoreductase and a reducible substance which transfers electrons which arise during the course of the determination reaction from the oxidoreductase onto an electrode and thus leads to a signal which is a measure for the analyte to be determined whereby the reducible substance is enzymatically reduced and oxidized at the electrode, which is characterized in that the substance which forms at the electrode by oxidation is different from the reducible substance used initially, as well as a corresponding sensor electrode system and the use of compounds suitable therefor. Finally new nitrosoaniline derivatives and a process for their production are also subject matter of the invention.

Abstract: A sparingly soluble salt of a heteropoly acid is used for the determination of an analyte which is an aromatic amine rich in electrons or together with another substance leads to such an amine. The analyte is determined by means of the heteropoly blue color formed.

Abstract: The present invention provides a process for the colorimetric determination of an analyte by means of enzymatic oxidation of the analyte in the presence of an electron acceptor and determination of the reduced electron acceptor by color formation as measure for the amount of the analyte, wherein the analyte is oxidized with an appropriate flavine- or PQQ-dependent oxidoreductase in the presence of aromatic nitroso or oxime compounds. The present invention also provides an agent for the colorimetric determination of an analyte by enzymatic oxidation of the analyte, containing flavine- or PQQ-dependent oxidoreductase and a color-forming electron acceptor, wherein the color-forming electron acceptor is an aromatic nitroso or oxime compound.

Abstract: The subject matter of the invention is a method for the electrochemical determination of an analyte in the presence of an oxidoreductase and a reducible substance which transfers electrons which arise during the course of the determination reaction from the oxidoreductase onto an electrode and thus leads to a signal which is a measure for the analyte to be determined whereby the reducible substance is enzymatically reduced and oxidized at the electrode, which is characterized in that the substance which forms at the electrode by oxidation is different from the reducible substance used initially, as well as a corresponding sensor electrode system and the use of compounds suitable therefor. Finally new nitrosoaniline derivatives and a process for their production are also subject matter of the invention.