| Research Abstract |
Polymer coated electrodes (PCEs), which consist of a metallic or carbon conductor direct coated with an ion-sensitive, electrocatalytic, or enzyme membrane, are very attractive potentiometric and amperometric sensors due to their simplicity of operation, superior amperometric response characteristics, capability of minimization, etc., compared with conventional membrane electrodes.
In this research, new amperometric sensors for determination of glucose and cholesterol based on bilayer film coating have been fabricated and their sensor characteristics under a steady-state condition have been examined. The glucose or cholesterol concentration could be monitored by measuring the current for H_2O_2 or O_2 reduction electrocatalyzed inner film where H_2O_2 was produced orO_2. was consumed by the enzyme reaction in the outer enzyme films. The reproducible relationship between glucose or cholesterol concentration and sensor output was obtained. The PCEs functioned as an electrochemical detecto
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r for flow injection analysis. Substantial unprovement in the selectivity of arnperometric detection for flow injection system was observed as a result of an electrostatic interaction between the positively charged electropolymerized film and analysis, that is, cationic species (e. g., dopamine, 1-norepinephrine and DL-3, 4-dihydroxyphenylalanine) exhibited little response, while the response of neutral and anionic species (e. g., 3, 4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylacetic acid and catechol) was only slightly changed at the polymer coated electrode compared with the bare electrode.
The complex admittance measurements of the quartz crystal oscillators with and without a film coating, which are in contact with air, moisture and supporting electrolyte aqueous media of various concentrations have been carried out over a frequency range covering the area of the resonant frequency of each oscillator system, and the results have been represented in the form of conductance and susceptance spectra (i. e., conductance vs. frequency plots and susceptance vs. frequency plots). According to the electrical equivalent circuit model conventionally proposed for a piezoelectric quartz crystal, the related circuit parameters (resistance R, inductance L, capacitance C and static capacitance C_0) have been evaluated, especially as a function of the concentration of supporting electrolyte. The change of electrolyte concentration-dependent swelling of the film was characterized by the evaluated parameters. It is demostrated that the method described can can apply the characterized kinematic viscosity and affinity sensing of the organic, inorganic and biological thin films. The quartz crystal microbalance (QCM) when operated in liquids was shown to retain its high mass sensitivity. The QCM has therefore been applied to the mass changes occurring during redox in thin polymer films. Solvent transport during electroneutrality requiring ion transport has been qualitatively demonstrated in the case of electrodes modified with thin film of poly (vinyferrocene), polyaniline, etc. Less
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