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A cyanide biosensor based on a pH-sensitive p-doped electrolyte-insulatorsemiconductor (EIS) structure with an immobilised enzyme (cyanidase) is realised at the laboratory scale. The immobilisation of the cyanidase is performed in two distinct steps: first, the covalent coupling of cyanidase to an N-hydroxysuccinimide-(NHS) activated Sepharose TM gel and then, the physical entrapment of NHS-activated Sepharose TM with the immobilised cyanidase in a dialysis membrane onto the EIS structure. The immobilisation of the cyanidase to the NHS-activated Sepharose TM is studied by means of gel electrophoresis measurements and investigations using an ammonia-(NH 3 ) selective electrode. For the electrochemical characterisation of the cyanide biosensor, capacitance/voltage and constant capacitance measurements, respectively, have been carried out. A differential measurement procedure is presented to evaluate the cyanide concentration-dependent biosensor signals.

A first step towards the microfabrication of a thin-film array based on an organic/inorganic sensor hybrid has been realized. The inorganic microsensor part incorporates a sensor membrane based on a chalcogenide glass material (CuAg-As-Se) prepared by pulsed laser deposition technique (PLD) combined with an PVC organic membrane-based organic microsensor part that includes an o-xylyene bis(N,N-diisobutyl-dithiocarbamate) ionophore. Both types of materials have been electrochemically evaluated as sensing materials for copper(II) ions. The integrated hybrid sensor array based on these sensing materials provides a linear Nernstian response covering the range 1 Â 10À1 of copper(II) ion concentration with a fast, reliable and reproducible response. The merit offered by the new type of thin-film hybrid array includes the high selectivity feature of the organic membrane-based thin-film microsensor part in addition to the high stability of the inorganic thin-film microsensor part. Moreover, the thin-film sensor hybrid has been successfully applied in flow-injection analysis (FIA) for the determination of copper(II) ions using a miniaturized home-made flow-through cell. Realization of the organic/inorganic thin-film sensor hybrid array facilitates the development of a promising sophisticated electronic tongue for recognition and classification of various liquid media.