Hydrogen peroxide sensor electrode system

Scheme of the detection cell of the hydrogen peroxide sensor expanded with the FIA system. The inner chamber has a 20-cm length and a 1-cm diameter (1) working electrode, (2) reference electrode, (3) counter electrode, (4) combined glass electrode, and (5) temperature sensor, surface of the working electrode equals 7 mm2. 

A thin film of manganese oxides deposited over a glassy earbon electrode dramatically lowers the overpotential for oxidation of various hydrazines ad hydrogen peroxide, thereby facilitating their amperometric detection in flow systems. Sensors based on this principle are highly sensitive and provide... 

The authors devoted their investigations to the development of a peroxidase-biomimetic sensor for determining trace quantities of ethyl alcohol in various solutions. In all tests the reaction system represented a mixture of microamounts of hydrogen peroxide and ethyl alcohol in an aqueous medium. The task was to determine the effect of the H202 C2H50H ratio on the detection ability of the biomimetic electrode. 

A similar approach was used for the detection of monosaccharides [56] pyranose oxidase delivered a suitable oxidase-based sensor with the hydrogen peroxide being determined again via the direct electron transfer from the carbon paste electrode to the enzyme horseradish peroxidase. In aU bi-enz5mie systems, both the enzymes were entrapped within the carbon paste. These electrodes were used as detectors in a liquid chromatography system allowing the simultaneous determination not only of several carbohydrates but also of ethanol within approximately 20 min. Ethanol production and carbohydrate consumption were monitored on-line during a fermentation of P. stipitis for 16 h (see also Section 11.2.3). 

Glucose measurements in urine and fermentation samples by means of GOD electrodes based on hydrogen peroxide detection usually suffer from interferences by anodically ox-idizable compounds. These can be oxidized in the measuring solution by reaction with hexa-cyanoferrate(III). However, the hexacyanoferrate(lI) ion formed is also oxidizable at an electrode potential of +600 mV. In order to prevent the hexacyanoferrate(II) from reaching the electrode, laccase has been co-immobilized with GOD in the sensor membrane [352]. Thus, the mediator is reoxidized in a laccase-catalyzed reaction with consumption of oxygen. The system is capable of shielding the electrode from ascorbic acid at concentrations up to 2 mmol/L. 

---