Short communication

Improvement of the adhesion of a Nafion® modifying layer on electrodes

Dithizone and its dicarboxylic acid derivative (DDz) have been immobilised onto gold films by both chemical attachment and incorporation into spin-coated polymer films. The modified gold films were characterised by ellipsometry. Surface plasmon resonance (SPR) was employed to monitor changes in the optical properties of the dithizone films in the presence of aqueous transition metal ions. The dependence of applied potential on the SPR response in the presence of metal ions has been studied in situ. It is shown that the technique can be used for the determination of metal ions in water.

Electrochemical sensors with an electrode system formed on a solid polymer electrolyte (spe) enable detection of substances in poorly conductive liquids and in gases and can be constructed either with a liquid phase as a part of the sensor system, or as solid-state sensors. The basic properties of spe, especially Nafion, are discussed as are the methods of preparation of electrodes on the spe surface. The effects of the geometry, preparation procedure and the character of the spe/electrode boundary on the sensor properties are examined. Principal sensor designs are described and discussed and selected applications are surveyed in the tables.

With the aim of developing a new type of immunoassay with electrochemical detection, a Nafion® film-modified electrode was used as an amplifying sensor to detect redox cationic labeled drugs by square-wave voltammetry. A series of amino drugs was labeled with three model redox labels, i.e. cationic cobaltocenium and procationic ferrocene and nitroxide groups. Several parameters were involved in the optimization of the analytical properties of the sensor, i.e. film processing and film thickness, accumulation time, ionic strength and ethanol content. The preconcentration of the labeled drugs was impeded by the competitive accumulation of hydrophobic amines. The accumulation process of the procationic labeled drugs was influenced significantly by the potential applied during accumulation, and their strong non-specific binding with proteins was observed in the presence of serum. Therefore the choice of cobaltocenium as a label was preferred. Optimized conditions were defined, which took into account these various aspects. The avidin-biotin system was proposed as an applicable extension of this approach.