Showing papers on "Amperometry published in 1992"
TL;DR: By co-immobilizing a hydrogen peroxide-producing oxidase with the peroxidase, amperometric biosensors can be made that respond to the substrate of the oxidase within a potential range essentially free of interfering electrochemical reactions.
Abstract: An apparent direct electron transfer between various electrode materials and peroxidases immobilized on the surface of the electrode has been reported in the last few years. An electrocatalytic reduction of hydrogen peroxide stars at about +600 mV versus a saturated calomel (reference) electrode (SCE) at neutral pH. The efficiency of the electrocatalytic current increases as the applied potential is made more negative and starts to level off at about –200 mV versus SCE. Amperometric biosensors for hydrogen peroxide can be constructed with these types of peroxidase modified electrodes. By co-immobilizing a hydrogen peroxide-producing oxidase with the peroxidase, amperometric biosensors can be made that respond to the substrate of the oxidase within a potential range essentially free of interfering electrochemical reactions. Examples of glucose, alcohol and amino acid sensors are shown.
351 citations
TL;DR: Electrooxidizable ascorbate, urate, and acetaminophen that interfere with amperometric glucose assays are completely and rapidly oxidized by hydrogen peroxide in a multilayer electrode.
Abstract: : Electrooxidizable ascorbate, urate and acetaminophen, that interfere with amperometric glucose assays are completely and rapidly oxidized by hydrogen peroxide in a multilayer electrode. The multilayer electrode is composed of an immobilized, but not electrically wired , horseradish peroxidase (HRP) film coated onto a film of electrically wired glucose oxidase (GOX). The wired enzyme is connected by a redox epoxy network to a vitreous carbon electrode. The current from the electrooxidizable interferants is decreased by their peroxidase-catalyzed Biosensors; Amperometric; Interferants. preoxidation by a factor of 2500 and the glucose/interferant current ratio is increased 103 fold. Undesired electroreduction of hydrogen peroxide can result when HRP is also wired to the electrode. Such unwanted 'wiring' is prevented by incorporating an electrically insulating barrier layer between the wired GO film and the HRP film. The hydrogen peroxide necessary for elimination of interferants can be added externally, or, when this is not possible, it can be generated in situ by means of a coupled enzyme reaction.
214 citations
TL;DR: Ink-jet printing has been demonstrated as a manufacturing technique that facilitates the rapid, reproducible and economical production of amperometric glucose biosensors as discussed by the authors, and Glucose was chosen as the...
161 citations
TL;DR: The determination of organophosphate and carbamate pesticides was carried out using cobalt phthalocyanine-modified carbon epoxy composite electrodes coupled with acetyl- or butyrylthiocholine as substrates and detection limits are similar as those obtained when analyses were performed using free cholinesterase and 10 min incubation with inhibitor.
152 citations
TL;DR: In this paper, a miniature glucose sensor (enzyme electrode) was developed, where glucose oxidase was immobilized by glutaraldehyde in albumin gel on a cellulose diacetate membrane.
Abstract: A rapid and simple method for the preparation of a miniature glucose sensor (enzyme electrode) has been developed. Glucose oxidase is immobilized by glutaraldehyde in albumin gel on a cellulose diacetate membrane. This membrane is directly attached to an H2O2 detecting electrode and covered with an external polyvinyl chloride membrane. The response time of the glucose electrode thus prepared is about 2 min, the calibration graph is linear for 0–30 mM glucose, and the sensor can be used repeatedly at room temperature for at least 10 days with small deterioration in response.
144 citations
TL;DR: In this article, the design, fabrication and evaluation of chemically modified screen-printed carbon electrodes are described with particular emphasis being placed on the practical details for sensor construction, and some preliminary results for the selective determination of reduced glutathione in human whole blood are also presented.
Abstract: The design, fabrication and evaluation of chemically modified screen-printed carbon electrodes is described with particular emphasis being placed on the practical details for sensor construction. This work employed cyclic and differential-pulse voltammetry, together with amperometry in stirred solutions to investigate systematically electrodes containing phthalocyanine and ferrocene-based mediators for the determination of several important biomolecules. An overview of the development of an amperometric assay using the enzyme glutathione peroxidase, and some preliminary results, for the selective determination of reduced glutathione in human whole blood is also presented.
104 citations
TL;DR: A method of immobilization was developed that provided an increase in the stability of the enzyme that enabled the determination of phenolic compounds using an enzyme electrode using the combination of the oxygen electrode and immobilized laccase.
97 citations
TL;DR: In this article, a novel glucose biosensor was prepared by deposition of a mixture containing glucose oxidase dissolved in water and Nafion dissolved in methanol at the surface of a platinum disk electrode.
Abstract: A novel glucose biosensor has been prepared by deposition of a mixture containing glucose oxidase dissolved in water and Nafion dissolved in methanol at the surface of a platinum disk electrode. Glucose concentration is evaiuated by measuring the amperometric current corresponding to hydrogen peroxide electrooxidation at 0.7 V vs. SCE. The addition of glucose oxidase to Nafion resulted in a Nafion-glucose oxidase film that was more permeable to anionic species than Nafion alone. The calibration curve for glucose is linear from 5 μM up to about 10 mM. In oxygen-saturated solution, the linear range extended to 15 mM. The optimum pH for the assay was found to be 5.5. The enzyme is not stabilized against temperature deactivation when it is immobilized in Nafion. The Pt/Nafion-glucose oxidase electrodes showed good stability when stored dry at room temperature with 80% of the initial response retained after 250 days.
94 citations
TL;DR: A glucose oxidase (GOD) electrode with ferrocene (Fc) used as an electron transfer mediator has been described in this article, where Fc was modified on a glassy carbon (GC) electrode surface, and the enzyme was then immobilized on the Fc-Nafion film.
83 citations
TL;DR: Galiatsatos et al. as mentioned in this paper described a glucose sensor utilizing the polypyrrole microtubules as mediator, which is highly selective with respect to other substrates and the sensor response is independent of oxygen concentration.
77 citations
TL;DR: In this paper, a cobalt-based glassy carbon (Co/GC) chemically modified electrode (CME) is described for use as an amperometric detector in the flow analysis of mono-, di- and trisaccharides.
TL;DR: A needle-type glucose sensor that can be used to determine glucose in serum and whole blood samples was developed in this article, where a platinum wire was used as the working electrode and a disposable hypodermic stainless-steel needle electroplated with platinum as the counter and reference electrode.
TL;DR: Bilayer conducting polymer electrodes, which consist of a polymetallophthalocyanine and polypyrrole incorporating glucose oxidase, showed catalytic behavior, which included an enhanced amperometric response current with the substrate and a significantly shifted oxidation potential of the response current.
Abstract: Bilayer conducting polymer electrodes, which consist of a polymetallophthalocyanine (PMePc) and polypyrrole incorporating glucose oxidase (PPy-GOx), were prepared on the glassy-carbon electrode by the successive electrochemical deposition of two different polymers. The bilayer film electrodes showed catalytic behavior, which included an enhanced amperometric response current with the substrate and a significantly shifted oxidation potential (approximately 700 mV) of the response current. The bilayer electrodes also showed a fast response time and good stability with the substrate. A bilayer microelectrode, which was prepared by using both PCuPc and PPy-GOx polymer films, also showed a good amperometric response with the substrate.
TL;DR: The storage stability of amperometric enzyme electrodes has been enhanced using a combination of a soluble, positively charged polymer, diethylaminoethyl (DEAE)-dextran and a sugar alcohol, lactitol, indicated by an increase in the shelf life of desiccated biosensors under conditions of thermal stress at 37°C.
TL;DR: In this article, the performance of a surface-adsorbed enzyme electrode for uric acid was investigated and the results showed that the enzyme exhibited no response to ascorbic acid at levels up to 0.53 mmol dm-3.
Abstract: Systematic voltammetric and amperometric studies have been undertaken to examine the electrochemical behaviour of uric acid at bare and surface-modified screen-printed electrodes. The precision of the electrode manufacture was determined by cyclic voltammetry with a 1.0 × 10–4 mol dm–3 uric acid solution and was calculated to be 6.0%(n= 5). Several strategies were investigated in an attempt to eliminate interference from ascorbic acid. These involved coating the electrode surface with Nafion, or the enzyme L-ascorbic acid oxidase. The latter was immobilized using one of two methods: either by a simple adsorption process, or by cross-linking with bovine serum albumin and glutaraldehyde. The amperometric response at the surface-adsorbed enzyme electrode for uric acid was linear over the concentration range from 5.08 × 10–6 to 1.51 × 10–4 mol dm–3; the limit of detection was 2.54 × 10–6 mol dm–3 using a full-scale deflection of 0.5 µA. This modified electrode exhibited no response to ascorbic acid at levels up to 0.53 mmol dm–3. The electrode modified by cross-linking the enzyme to the surface showed no response to ascorbic acid concentrations of up to 0.093 mmol dm–3.
TL;DR: A reversed-phase ion-pair HPLC method for the separation of four aminoglycosides was developed using volatile ion- Pairing agents and optimized for detection with an ion spray HPLC-MS interface.
TL;DR: A Prussian Blue-modified glassy carbon electrode prepared by simple adsorption exhibited excellent electrocatalytic activity in the oxidation of hydrazine in acidic media.
TL;DR: In this paper, the authors described the characterization and optimization of bovine erythrocyte glutathione peroxidase, together with its application in an assay employing amperometry in stirred solutions for the determination of endogenous levels of reduced glutathion (GSH).
Abstract: The systematic characterization and optimization of bovine erythrocyte glutathione peroxidase is described, together with its application in an assay employing amperometry in stirred solutions for the determination of endogenous levels of reduced glutathione (GSH). Initial studies employed UV spectroscopy, cyclic voltammetry, and amperometry in stirred solutions (to construct hydrodynamic voltammograms) for several investigations including the selection of a suitable hydroperoxide second substrate, the investigation of solution conditions on the enzyme reaction rate, and reconstituted enzyme stability. Subsequently, amperometry in stirred solutions was used to monitor the enzyme-catalyzed rate of GSH oxidation and to construct calibration plots over the concentration range 10 to 50 μM (corresponding to normal circulating GSH levels after the envisaged sample preparation step consisting of a simple twenty fold dilution of whole blood). Enzyme selectivity studies were performed using several potential physiological interferents and selected pharmaceuticals that may be encountered in the circulation of patients being treated for rheumatoid arthritis. The coefficient of variation for the enzyme linked amperometric assay was 7.28% (n = 5) for solutions containing 40 μM GSH.
TL;DR: In this paper, an amperometric horseradish peroxidase electrode is described for the determination of hydrogen peroxide in organic solvents, which can be operated in dioxane, chloroform and chlorobenzene, the presence of a small quantity of aqueous buffer being essential for activity.
Abstract: An amperometric horseradish peroxidase electrode is described for the determination of hydrogen peroxide in organic solvents. The enzyme was co-adsorbed with an electron mediator, hexacyanoferrate(II), to the surface of a graphite foil electrode making reagentless measurement possible. The electrochemical reduction of the enzymatically oxidized mediator was utilized as the analytical signal. The electrode can be operated in dioxane, chloroform and chlorobenzene, the presence of a small quantity of aqueous buffer being essential for activity. On this basis a small, probe-type sensor has been assembled the response of which is linearly related to hydrogen peroxide concentration between 0.05 and 1 mM. A tyrosinase sensor has been constructed by combining a Clark-type oxygen electrode with a membrane bearing adsorbed enzyme. The sensor is capable of measuring between 0.1 and 5 mM phenol in chloroform saturated with aqueous buffer.
TL;DR: In this article, the authors review the current state of membrane electrode probes and present a review of the state-of-the-art of membrane electrodes for ion-selective electrophoresis.
Abstract: Membrane electrodes are relatively simple electrochemical devices that can be used for the direct measurement of ions, gases, and biomolecules in complex samples Selectivity for one species over another is determined by the nature and chemical composition of the membranes and associated reaction layers used to fabricate the devices All membrane electrode probes employ at least one ion-selective membrane as the ultimate transduction element This indicator membrane serves as an additional component of a classic two-electrode galvanic cell The potential developed at the membrane/sample interface is directly or indirectly related to the activity or concentration of analyte in the sample Because cell potentials are detected under essentially zero-current conditions, analytical measurements with these probes are generally not subject to the mass transfer and electron transfer kinetic limitations that often plague voltammetric or amperometric techniques In this report, we review the current state
TL;DR: Electro-deposition provides the added advantage that it lends itself to the preparation of multi-enzyme/multi-analyte electrodes by the adsorption of different enzymes to separate gold sols, followed by sequential electrodeposition onto discrete areas of a multichannel electrode.
TL;DR: In this article, an amperometric flow-through electrode based on ion transfer across the interface of two immiscible electrolyte solutions was developed, and a hydrophilic cellulose membrane was utilized to stabilize the interface between the flowing aqueous solution and the stationary organic phase.
TL;DR: The cobalt tetraphenylporphyrin modified glassy-carbon electrode at 750 degrees (HCME) is shown to catalyze the electrooxidation of hydrazine and was excellent in acidic solution and even in solutions containing organic solvent.
TL;DR: In this paper, cyclic and pulsed voltammetry at a rotated disk electrode and a pulsed amperometric detection (PAD) in a flow-injection cell were applied in studies of the anodic response of thiourea at gold electrodes in 0.1 M NaOH.
23 Apr 1992
TL;DR: The role of polymeric materials in the fabrication of Ion-Selective Electrodes and Biosensors is discussed in this paper, where an ion-selective electropolymerized film is used as a biosensor.
Abstract: Overview of Biosensors Multienzyme Sensors Biosensors Based on Entrapment of Enzymes in a Water-Dispersed Anionic Polymer Electrochemical Characterization of Ferrocene Derivatives in a Perfluoropolymer Glucose Oxidase Electrode Protein Stabilization in Biosensor Systems Electrocatalytic Oxidation of Nicotinamide Adenine Dinucleotide Cofactor at Chemically Modified Electrodes Preparation and Characterization of Active Glucose Oxidase Immobilized to a Plasma-Polymerized Film Role of Polymeric Materials in the Fabrication of Ion-Selective Electrodes and Biosensors Electrical Wiring of Flavoenzymes with Flexible Redox Polymers Permselective Coatings for Amperometric Biosensing Polypyrrole Film Electrode Incorporating Glucose Oxidase: Electrochemical Behavior, Catalytic Response to Glucose, and Selectivity to Pharmaceutical Drugs Analytical Applications of the Electrochemical Quartz Crystal Microbalance Electrochemically Prepared Polyelectrolyte Complex of Polypyrrole and a Flavin-Containing Polyanion: Use as a Biosensor Development of Polymer Membrane Anion-Selective Electrodes Based on Molecular Recognition Principles Electropolymerized Films for the Construction of Ultramicrobiosensors and Electron-Mediated Amperometric Biosensors Molecular Materials for the Transduction of Chemical Information into Electronic Signals by Chemical Field-Effect Transistors Chemically Sensitive Microelectrochemical Devices: New Approaches to Sensors Macro- to Microelectrodes for In Vivo Cardiovascular Measurements Polymeric Matrix Membrane Field-Effect Transistors: Sodium Ion Sensors for Medical Applications Polymeric Membranes for Miniature Biosensors and Chemical Sensors Thick-Film Multilayer Ion Sensors for Biomedical Applications Environmentally Sensitive Polymers as Biosensors: The Glucose-Sensitive Membrane Water and the Ion-Selective Electrode Membrane Swelling of a Polymer Membrane for Use in a Glucose Biosensor Optical Immunosensors Using Controlled-Release Polymers
TL;DR: In this article, cyclic voltammetry was used to study the oxidation of vitamin D2(ergocalciferol) and vitamin D3(cholecalciferols) at a planar glassy carbon electrode.
Abstract: Cyclic voltammetry was used to study the oxidation of vitamin D2(ergocalciferol) and vitamin D3(cholecalciferol) at a planar glassy carbon electrode. The electrode reaction for cholecalciferol was found to be dependent on the apparent pH between 4.95 and 6.10, and pH independent between pH 6.10 and 8.65 when the solutions contained 90% methanol; this suggested a pKa value of 6.10 for vitamin D3. Similar behaviour was exhibited by ergocalciferol, and a pKa value of 6.35 was found. The peak currents for both vitamins were found to be dependent on the methanol concentration of the supporting electrolyte. The peak currents were also found to be dependent on the ionic strength of the acetate buffer (pH 6.0) over the range 0.1–1.0 mol dm–3. Both substances were oxidized in one step, which was found to be an irreversible reaction; the final product for vitamin D2 can undergo absorption at the electrode surface. The parent compounds could be undergoing oxidation at the triene moieties. The optimum mobile phase for liquid chromatography with amperometric detection was found to be 95% methanol–0.05 mol dm–3 acetate buffer (pH 6.0); the detector was operated at a potential of + 1.3 V (versus Ag—AgCl), and a linear response was obtained for vitamin D3 over the range from 10 to 100 ng injected; for vitamin D2 the response was linear from 20 to 200 ng injected. Extracts of pharmaceutical products were separated on reversed-phase columns prior to amperometric detection of the vitamins. Cholecalciferol was successfully determined in a multivitamin table, and ergocalciferol in a multivitamin liquid preparation.
TL;DR: The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor, which provides a linear response to glucose over a wide concentration range.
Abstract: Amperometric enzyme electrode for glucose is described based on the incorporation of glucose oxidase (GOD) into graphite paste modified with tetracyanoquinodimethane (TCNQ). The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor (1). The sensor provides a linear response to glucose over a wide concentration range. The response time of the sensor is 15-50 sec, and the detection limit is 0.5 mM. Stable response to the substrate was obtained during a period of 35 d. Application of the sensor in the plasma analysis is reported.
TL;DR: An enzyme electrode was constructed for amperometric determination of xylose and glucose based on the PQQ-dependent membrane-bound aldose dehydrogenase (ALDH) from Gluconobacter oxydans and showed fairly good stability.
TL;DR: An amperometric electrode sensitive to pyruvate based on methylene green as mediator and on carbon paste chemically modified with pyruveate oxidase is described in this paper.