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A high sensitive detection method allows the direct determination of Pt2+/Pt4+ within a concentration range of ng/l (pptj. The procedure was used to establish the development of soluble platinum species during constant or dynamic polarisation of platinum electrodes in phosphate buffered saline solution.Platinum showed some properties of a passive metal. In the passivated state the dissolution was influenced by a surface film. Furthermore a soluble platinum species was found to be produced during the reduction of the surface oxide. These results confirmed by direct evidence the conclusions of earlier investigations concerning the corrosion of platinum based on electrochemical measurements.Eine hochernpfindliche Analysenmethode ermoglicht die direkte Bestimmung von Pt2+/Pt4+ bis in den Konzentrationsbereich von ng/l (pptj. Mit dem Verfahren wurde die Entstehung liislicher Platinspezies beim konstanten und dynamischen Polarisieren von Platinelektroden in phosphatgepufferter Kochsalzlosung nachgewiesen.Platin zeigte Eigenschaften eines passivierbaren Metalles. In passiviertem Zustand wurde das In-Losung-gehen des Metalles durch einen Oberflachenfilm minimiert. Desweiteren entstand eine Iosliche Platinspezies im Verlauf der Reduktion des Oherflachenoxides. Die Ergebnisse bestatigten die aufgrund elektrochemischer Messungen getroffenen Schlusse zur Platinkorrosion friiherer Untersuchungen mit direktem Nachweis.

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An electrocatalytic glucose sensor for in vivo application has been developed. The sensor is a flow-through cell with three electrodes and can be integrated into a blood vessel. The principle of measurement is based on the direct electrochemical oxidation of glucose at a membrane-covered noble-metal electrode. To test the potential long-term in vivo function of the sensor, it was implanted in the carotid artery of a sheep. Thus, the sensor performance was verified over a period of 71 days. During this time, a nearly constant blood flow through the cell was achieved, which indicates good blood compatibility of the materials used. It was possible to set up a calibration that was valid over 24 days (mean error 2.3 mmol l-1). The tested cross-sensitivity of the sensor towards cysteine, acetyl salicylic acid and other small molecules shows tolerable effects on this type of glucose measurement. Only high concentrations of lactate and ethanol require a special adaptation of the calibration to suppress their influence. Minor cross-sensitivity and promising long-term stability recommend this type of sensor for in vivo monitoring of blood sugar level. However, for intravasal application, it is necessary to modify the present sensor design to a catheter-type construction.