Bienzymatic amperometric biosensor for glucose based on polypyrrole/ceramic carbon as electrode material

A novel amperometric biosensor utilizing two enzymes, glucose oxidase (GOD) and horseradish peroxidase (HRP), was developed for the cathodic detection of glucose. The glucose biosensor was constructed by electrochemical formation of a polypyrrole (PPy) membrane in the presence of GOD on the surface of a HRP-modified sol-gel derived-mediated ceramic carbon electrode. Ferrocenecarboxylic acid (FCA) was used as mediator to transfer electron between enzyme and electrode. In the hetero-bilayer configuration of electrode, all enzymes were well immobilized in electrode matrices and showed favorable enzymatic activities. The amperometric detection of glucose was carried out at +0.16 V (versus saturated calomel reference electrode (SCE)) in 0.1 M phosphate buffer solution (pH 6.9) with a linear response range between 8.0 x 10(-5) and 1.3 x 10(-3) M glucose. The biosensor showed a good suppression of interference in the amperometric detection.

Surface renewable graphite organosilicate composite electrode containing indium(III) hexacyanoferrate(II/III)

Indium(III) hexacyanoferrate(II/III) (InHCF) supported on graphite powder was prepared using the in situ chemical deposition procedure and subsequently dispersed into methyltrimethoxysilane-derived gels to yield a conductive graphite organosilicate composite. The composite was used as the electrode material to fabricate a three-dimensional InHCF-modified electrode. InHCF acts as a catalyst, graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. The chemically modified electrode can electrocatalyze the oxidation of thiosulfate, and exhibits a good repeatability of surface-renewal by simple mechanical polishing, as well as simple preparation, good chemical and mechanical stability.

Renewable manganous hexacyanoferrate-modified graphite organosilicate composite electrode and its electrocatalytic oxidation of L-cysteine

Manganous hexacyanoferrate (MnHCF) supported on graphite powder was dispersed into methyltrimethoxysilane-derived gels to yield a conductive composite, which was used as electrode material to construct a renewable three-dimensional MnHCF-modifed electrode. MnHCF acts as a catalyst, graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone, and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. Cyclic voltammetry was exploited to investigate the dependence of electrochemical behavior on supporting electrolytes containing various cations. The chemically modified electrode can electrocatalytically oxidize L-cysteine, and exhibits a distinct advantage of polishing in the event of surface fouling, as well as simple preparation, good chemical and mechanical stability, and good repeatability of surface renewal.

Surface-renewable cobalt(II) hexacyanoferrate-modified graphite organosilicate electrode and its electrocatalytic oxidation of thiosulfate

Cobalt(II) hexacyanoferrate (CoHCF) was deposited on graphite powder by an in situ chemical deposition procedure and then dispersed into methyltrimethoxysilane-derived gels to prepare a surface-renewable CoHCF-modified electrode. The electrochemical behavior of the modified electrode in different supporting electrolyte solutions was characterized by cyclic voltammetry. In addition, square-wave voltammetry was employed to investigate the pNa-dependent electrochemical behavior of the electrode. The CoHCF-modified electrode showed a high electrocatalytic activity toward thiosulfate oxidation and could thus be used as an amperometric thiosulfate sensor.

Detection of menadione sodium bisulfite (vitamin K-3) by reversed-phase high performance liquid chromatography with series dual-electrode amperometric detector

A reversed-phase high-performance liquid chromatography with series dual glassy carbon electrodes for the amperometric detection of water-soluble menadione is described. The complex post-column derivatization reaction and the high background currents were avoided. The menadione sodium bisulfite was reduced at -0.3 V vs. SCE at the upstream (generator) electrode and oxidized at +0.2V vs. SCE at the downstream (collector) electrode. The mobile phase was 0.2moll(-1) HAc-NaAc aqueous buffer (pH 5.50) and 40% (v/v) methanol. The linear response was in the range of 35 ng to 15 mu g, with a detection Limit of 15 ng (S/N=3). The correlation coefficient was 0.9997 (n=6). The electrochemical detection with series dual electrodes has a higher selectivity for menadione (vitamin K-3) compound than with UV detection.

Detection of hydrazine, methylhydrazine, and isoniazid by capillary electrophoresis with a palladium modified microdisk array electrode

A palladium particle-modified carbon fiber microdisk array electrode was designed and employed in capillary electrophoresis for the simultaneous detection of hydrazine, methylhydrazine, and isoniazid. The Pd-modified microdisk electrode had high catalytic ability for hydrazines and exhibited good reproducibility and stability. The response for hydrazine was linear over 3 orders of magnitude with a correlation coefficient of 0.993. The detection limits far hydrazine, methylhydrazine, and isoniazid were 1.2, 2.1, and 6.2 pg, respectively.

Scanning tunneling microscopy characterization of electrode materials in electrochemistry

Ex situ and in situ STM characterization of the electrode materials, including HOPG, GC, Au, Pt and other electrodes, is briefly surveyed and critically evaluated. The relationship between the electrode activity and surface microtopography is discussed.

CATALYTIC-OXIDATION AND FLOW DETECTION OF ACETAMINOPHEN AT A DICYANOBIS(1,10-PHENANTHROLINE)IRON(II)-MODIFIED ELECTRODE

Dicyanobis(1,10-phenanthroline)iron(II)-modified glassy carbon electrodes were shown to exhibit an electrocatalytic response for the oxidation of acetaminophen with a decrease of 100 mV in the potential required. It can also inhibit the oxidation of ascor

ELECTROOXIDATION OF ASCORBIC-ACID AT THE BIS(4-PYRIDYL) DISULFIDE MODIFIED GOLD ELECTRODE

The electrooxidation of ascorbic acid (AA) at the bis(4-pyridyl)disulfide (PySSPy) modified gold electrode was studied. The results showed that the oxidation process was pH-dependent. It was mainly due to the static interaction between AA and the modified

POLYANILINE-DISPERSED MERCURY-ELECTRODE FOR THE DETECTION OF MONOCHLORAMINE AND DICHLORAMINE

A novel type of electrochemical detector based on a polyaniline-dispersed mercury-coated glassy carbon chemically modified electrode was investigated for the detection of monochloramine and dichloramine. A polyaniline dispersed-mercury modified electrode, which was prepared by coating polyaniline on a thin mercury film electrode using fast-sweep voltammetry, was developed. The selectivity could be altered using various counter ions incorporated into the polymer. The results indicated that the use of a conducting polymer-based electrochemical sensor for the selective determination of chloramine is a feasible approach.

ELECTROCHEMICAL-BEHAVIOR OF HEXACYANOFERRATE(II) ON A GOLD ELECTRODE MODIFIED WITH BIS(4-PYRIDYL)DISULFIDE

The electrochemical behaviour of hexacyanoferrate(II) has been studied by using a bis(4-pyridyl)disulfide modified gold electrode. On the protonated electrode surface, hexacyanoferrate(II) can transfer an electron reversibly but no apparent adsorption was detected. On the deprotonated electrode surface, electron transfer by hexacyanoferrate(II) was more difficult. The electrochemical reversibility varied with the pH of the solution. Relationships between the currents or the standard heterogeneous rate constants and pH were derived.

ISOPOLYMOLYBDIC ACID-POLY(4-VINYL)PYRIDINE FILM MODIFIED ELECTRODE

Electrochemical polymerization of 4-vinylpyridine produced a uniform poly(4-vinyl)pyridine(PVP) film on the glassy carbon (GC) electrode surface. The isopolymolybdic acid-PVP film-modified electrode was prepared by soaking the PVP/GC electrode in the 0.05 M H2SO4 aqueous solution containing 0.005 M isopolymolybdic acid (H4Mo8O26). The latter (catalyst) is incorporated and held in the PVP film electrostatically. The electrochemical behavior and electrocatalytic properties of this H4Mo8O26-PVP/GC electrode was described. The results indicate that this modified electrode has good stability and electrocatalytic activity on the reduction of chlorate and bromate ions in aqueous solution. The catalytic process is regarded as an EC mechanism.

CATALYTIC REDUCTION OF HEMOGLOBIN AT THIONINE CHEMICALLY MODIFIED ELECTRODE AND FIA APPLICATIONS

Thionine-containing chemically modified electrode (cme) was constructed with glassy carbon substrate by potential sweep oxidation, electrodeposition and adsorption procedures, and electrocatalytic reduction of hemoglobin was carried out and characterized at the cme under batch and flow conditions. Comparison of the catalytic response toward hemoglobir obtained at the cme was made mainly in terms of the potential dependence, the detectability and long-term stability. When used in flow injection analysis (FIA) experiments with the detector monitored at a constant potential applied at -0.35 V vs sce, detection limit of 0.15-1.5 pmol level of hemoglobin injected was achieved at the cme, with linear response range over 2 orders of magnitude. All the cme s retained more than 70% of their initial hemoglobin response level over 8 h of continuous service in the flow-through system.

AMPEROMETRIC DETECTION OF CATECHOLAMINES WITH LIQUID-CHROMATOGRAPHY AT A NOVELLY CONSTRUCTED PRUSSIAN BLUE CHEMICALLY MODIFIED ELECTRODE

A novel Prussian blue chemically modified electrode (CME) was constructed and characterized for liquid chromatography electrochemical detection (LCEC) of catecholamines. Both anodic and cathodic peaks could be obtained by monitoring at constant applied potential at anodic and slightly cathodic potential ranges (0.3-0.7 and -0.2-0.1 V vs. SCE), respectively. When arranged in a series configuration, using the modified electrodes as generating and collecting detectors, extremely high effective collection efficiencies of 0.91 (for norepinephrine) and 0.58 (for dihydroxyphenylacetic acid) were achieved in dual-electrode LCEC for catecholamines; and a linear response range over 3 orders of magnitude and a detection limit of 10 pg were obtained with a downstream CME as the indicating detector.

ELECTROCHEMICAL STUDY OF ISOPOLYOXOMETALLATES AND HETEROPOLYOXOMETALLATES FILM MODIFIED MICROELECTRODES .1. PRETREATMENT AND MODIFICATION OF THE MO80-26(4-) MODIFIED CARBON-FIBER MICROELECTRODE

In this paper the preparation of isopoly- and heteropolyoxometallates (IPA and HPA) thin film modified carbon fiber (CF) microelectrodes and the factor that influences the modification of IPA and HPA films are described. IPA and HPA film modified CF microelectrodes can all be prepared by cyclic potential scan and simple dip coating. The modified electrodes prepared are very stable and reversible in acidic solution with monolayer characteristics. The electrochemical pretreatment of CF microelectrodes plays an important role in the modification of IPA and HPA film. The absorption of IPA and HPA film on electrode surfaces has been discussed on the basis of surface conditions of the CF microelectrode and the structure of IPA and HPA.