Showing papers on "Reference electrode published in 1992"

Combination monophasic action potential/ablation catheter and high-performance filter system

Abstract: A combination catheter for both detecting monophasic action potentials and ablating surface tissue in an in vivo heart of a patient is provided. The apparatus includes a catheter probe having a terminal tip portion (10) and an electrode (20) carried on the tip such that a portion of the tip electrode (20) is exposed to ambient. A reference electrode (50) is spaced along the tip from the first electrode for supplying a reference potential signal. An ablating electrode (30) is located adjacent to but electrically insulated from both the tip (20) and reference (50) electrodes for providing electromagnetic energy to the tip. The electrodes are electrically connected to the proximal end of the catheter through individual conductors or wires (22, 32, and 50) that run through an insulated cable. An electronic filter is provided to permit the recording of MAPs during ablation without radiofrequency interference. The catheter may also include standard mapping and/or pacing electrodes (80 and 75) respectively. The catheter may further include a steering mechanism for positioning the catheter at various treatment sites in the heart, and a structure for holding the tip electrode in substantially perpendicular contact with heart tissue with a positive pressure, and for spacing the reference electrode from the heart tissue.

A biosensor and a method for measuring a concentration of a substrate in a sample

Abstract: The present invention provides a biosensor comprising an electrical insulating substrate, a main electrode system formed on the substrate and having a working electrode and a counter electrode, a reaction layer provided in contact with or in the vicinity of the main electrode system and containing an oxidoreductase, and a sub electrode system as a reference provided with an interval from the main electrode system and having a working electrode and a counter electrode.

Electrochemistry at .omega.-hydroxy thiol coated electrodes. 3. Voltage independence of the electron tunneling barrier and measurements of redox kinetics at large overpotentials

Abstract: Self-assembled monolayers of ω-hydroxy thiols on Au electrodes are investigated as electron tunneling barriers allowing the measurement of heterogeneous electron kinetics of solution species over a wide range of electrode potentials without mass transport limitations. From the dependence of the electron-transfer rate of a series of redox couples on the thickness of the monolayer film, a more precise tunneling coefficient, β, of 1.08±0.20 per methylene unit in the ω-hydroxy thiol was measured independent of the redox couple and was found to be nearly independent of the electrode potential

Biosensor utilizing enzyme and a method for producing the same

Abstract: The biosensor of the present invention quantifies a substrate contained in a sample liquid by reducing electron acceptors using electron generated in a reaction of the substrate to enzyme and then by measuring the reduced amount of the electron acceptors electrochemically. The biosensor has an electrical insulating substrate, an electrode system including at least a working electrode and a counter electrode, a reaction layer including the enzyme provided on the electrode system and a hydrogen ion concentration control layer, and the reaction layer is in contact with the electrode system. According to the present invention, the hydrogen ion concentration in the sample liquid can be made most appropriate in accordance with the type of the enzyme contained in the reaction layer, without the adjustment of the hydrogen ion concentration in the sample liquid beforehand. Thus, the specific substrate contained in the sample liquid can be easily quantified with accuracy and speed.

A dialysis electrode device

Abstract: A dialysis electrode device comprises a shank of needle-like proportions and formed from a hollow dialysis fiber membrane. The shank is closed at its distal end by a sealing plug and, at its proximal end, it is sealed to and in communication with an auxiliary chamber defined by a tubular body part. Electrolyte is supplied to the chamber in the shank through an inlet conduit and is removed via an outlet conduit connected to the auxiliary chamber. The device also includes a dialysis or first working electrode, which is insulated save for a length thereof disposed within the hollow shank, a counter electrode and a reference electrode mounted within the auxiliary chamber. It may be used in clinical medicine and the food, pharmaceutical and other industries where it is desirable to analyze or monitor the presence of chemical substances. In carrying out a microdialysis procedure in human tissue, for example, the device is primed with an enzyme electrolyte solution and electrical measurements are taken, in situ, of the concentration of a chemical substance diffusing into the shank chamber through the dialysis fiber shank.

A Novel Method for Generating Quantitative Local Electrochemical Impedance Spectroscopy

Abstract: A local electrochemical impedance spectroscopy (LEIS) technique for mapping the ac impedance distribution, as a function of frequency, of an electrode has been developed. In LEIS, as in traditional ac impedance methods, a sinusoidal voltage perturbation between the working and reference electrode is maintained by driving an ac current between the working electrode and a distant counterelectrode with a potentiostat. Local ac impedances are then derived from the ratio of the applied ac voltage and the local ac solution current density. The local ac current density is obtained from potential difference measurements near the electrode surface using a probe consisting of two micro‐electrodes. By measuring the ac potential difference between the micro‐electrodes, and knowing their separation distance and the solution conductivity, the local ac solution current density is derived. The accuracy of the local ac impedance data generated with this technique was established by investigating two model systems. The first provided a homogeneous electrode which allowed LEIS measurements to be compared to traditional EIS, while the second system provided a heterogeneity of known size and location whose components were easily characterized with traditional techniques. It is shown that area‐normalized scanning ac impedance measurements of the homogeneous electrode agreed well with traditional results. In addition, because LEIS maps the impedance properties of an electrode, the defect in the heterogeneous electrode was easily detected, while traditional ac impedance of this electrode gave little indication of its presence.

Heart mapping catheter

Abstract: A mapping catheter assembly 10 including a flexible lead body 12 and a deformable lead body 14. A lumen 22 is provided to accept a reference catheter 18 which includes a distal tip electrode assembly 29. In use an array 16 of electrode sites are deformed into a spherical shape after the assembly is placed in a heart chamber. The reference electrode assembly 29 is advanced into contact with the heart wall to provide calibration information for the array 16.

Method of using enzyme electrode

Abstract: Disclosed is a method of assaying a high concentration of a substance in a liquid sample with a polarographic cell. The cell contains an electrode assembly that includes a reference electrode and a hydrogen peroxide sensor electrode having a laminated membrane covering the liquid sample contacting face of the sensor electrode. The laminated membrane includes an outer membrane permeable to the substance and oxygen, an inner membrane permeable to hydrogen peroxide and located adjacent the face of the sensor electrode, and an enzyme layer between the inner and outer membrane; the enzyme in the enzyme layer can oxidize the substance to generate hydrogen peroxide. The method includes contacting the outer membrane with the liquid sample; permitting the substance and oxygen in the liquid sample to pass through the outer membrane to contact the enzyme layer so that where the substance is oxidized to generate hydrogen peroxide; permitting the generated hydrogen peroxide to pass through the inner membrane to contact the sensor electrode; and ensuring that the supply of oxygen in the enzyme layer relative to the supply of glucose is sufficient to produce an equilibrium concentration of hydrogen peroxide, which generates a steady state response at the sensor electrode proportional to the concentration of the substance in the liquid sample.

Electrochemical gas sensor cells using three dimensional sensing electrodes

Abstract: An electrochemical gas sensor cell is provided, the use of which permits quantitative measurement of volatile gas contaminants in an atmosphere being monitored. The cell comprises at least a first sensor electrode and a second counter electrode, on either side of an ion conductive electrolyte which may be immobilized in a matrix. The electrolyte may also be a solid electrolyte or a polymer electrolyte. The sensing electrode has a high surface area catalyst dispersed on a porous substrate, and is mounted in such a manner as to be exposed to the atmosphere which is to be sensed for gaseous contaminants, with the counter electrode being isolated from any exposure to that atmosphere. Generally, the electrodes are mounted in electrically conductive frames, sandwiching a third non-conductive frame member in which the ion conductive electrolyte is substantially located. The conductive frames may comprise electronically conductive materials such as conductive polymers, ceramics, nitrides, oxides and graphites. In an alternative embodiment, a further reference electrode may be mounted so as to be exposed to the electrolyte. The porous electrode may comprise a porous substrate or a base layer, a catalytically active metal, alloy, or metal oxide (usually a noble metal) dispersed in a high surface area form, carbon, and a polymeric hydrophobic binder.

X-ray transparent monitoring electrode and method for making

Abstract: A biomedical monitoring electrode assembly including an X-ray translucent multi-element back electrode assembly adapted to be adhesively attached to the body of a patient, and a reference electrode adapted for positioning remote from the back electrode, preferably on the limb of a patient. An X-ray translucent lead wire assembly is attached to the back electrode assembly with two of the leads connected to the two electrodes of the back electrode assembly and another lead extending from the back electrode assembly to the remote reference electrode.

Nucleation and Morphology Studies of Aluminum Deposited from an Ambient‐Temperature Chloroaluminate Molten Salt

Abstract: Aluminium deposition from AlCl 3 :MEIC (1-methyl-3-ethylimidazolium chloride) has been studied employing an inverted optical microscope to perform in situ optical observations during the deposition process at a 250 μm diam tungsten electrode. Thin, continuous aluminum coatings with nuclei (or cluster) sizes below optical microscopic resolution are produced from a 1.1:1.0 AlCl 3 :MEIC molten salt using constant potential deposition at potentials ≤-0.2 vs. an Al(III)/Al reference electrode

Means for measuring a characteristic in a sample fluid

Abstract: A measuring device, intended for measurements on whole blood, comprises a sample fluid chamber for containing a blood sample, ion-selective potentiometric electrodes for measurement of the concentrations of sodium and potassium ions, a reference potentiometric electrode, an optical sensor for measuring the concentration of glucose by means of a color reaction, a cuvette having a window permitting spectrophotometric measurement of the level of haemoglobin, a conditioning (calibration) fluid chamber in which the ion-selective electrodes and the reference electrode are exposed to a conditioning (calibration) fluid comprising known concentrations of sodium and potassium ions (thereby facilitating calibration of the response of the ion-selective electrodes), a rupturable pack containing the conditioning fluid and from which the fluid is released into the conditioning fluid chamber upon application of pressure to the pack, and a wall part which partly defines the sample fluid chamber and has weakened areas which are ruptured upon movement of the sensors (i.e. the electrodes and the glucose sensor) so as bring the sensors into contact with the blood sample and which establishes a seal around the sensors.

Micro-electrode and method for preparing it

Abstract: A working micro-electrode with a reference electrode prepared by coating a working micro-electrode with an insulating material except a working electrode portion, forming a silver layer on the coated surface, and then changing a portion of the silver layer into silver chloride which is the reference electrode; a working micro-electrode with a reference electrode and a counter electrode prepared by coating the working micro-electrode with the reference electrode with an insulating material, and then forming the counter electrode on the surface of the insulating material; and methods for preparing these composite micro-electrodes. Heretofore, even if the working electrode is thinly constituted, the merit of the micro-electrode has not been sufficiently utilized, since the reference electrode and the counter electrode have been thick. However, the present invention can solve this problem and can facilitate experiments in which the micro-electrode is necessary. Since an inexpensive material such as carbon can be used, the working electrode may be constituted so as to be disposable or can be cut off the used portion to repeatedly obtain a new electrode surface. Therefore, the working electrode of the present invention is economical.

Measurement of pH in subcritical and supercritical aqueous systems

Abstract: The use of yttria-stabilized zirconia (YSZ) electrodes of the type Hg/HgO/ZrO2(Y2O3)/H+, for measuring pH in aqueous solutions at high subcritical (150 374°C) is reviewed. The construction and operation of the YSZ and reference electrodes employed in these studies are described and their application in measuring the pH of a variety of technologically-important aqueous system is discussed. We show that the YSZ electrode is thermodynamically viable at temperatures into the supercritical region, and that it is a primary pH sensor in that calibration is not necessary, provided that the activity of water is known. However, highly accurate pH measurements at high subcritical and supercritical temperatures will require the development of more accurate reference electrodes.

Scanning electrochemical microscopy: potentiometric probing of ion fluxes

Abstract: The scanning electrochemical microscope has been used to probe the diffusion layer by measuring the potential difference between a large reference electrode located in the bulk of the solution and a microindicator electrode positioned a few µm away from a substrate electrode Ag microdiscs (10 and 50 µm diameter) have been used as potentiometric sensors to probe the concentration profile due to the diffusion of Ag+ to and from a planar Ag electrode A similar experiment was carried out with an Ag microcylinder (50 µm diameter) as substrate electrode In a separate set of experiments, Ag/AgCl microdiscs (10 and 50 µm diameter) were used to monitor the flux of Cl– consumed and generated by a film of polyaniline electrodeposited on Pt The tip potential was recorded while cycling the potential of the PANI film past the first oxidation peak Direct measurement of the ingress and egress of Cl– ions supports previously reported mechanisms for the oxidation of PANI films

Molecular interface for an activity controlled enzyme electrode and its application for the determination of fructose

Abstract: A PQQ enzyme (fructose dehydrogenase) is electronically adsorbed into a monolayer and then immobilized on a platinum electrode surface by electroxidative polymerization of polypyrrole. The conductive polymer matrix works as an interface that serves as an electron-shuttling medium between the enzyme and the electrode as well as the matrix for enzyme immobilization. The enzyme electrode demonstrates that the PQQ enzyme is rapidly turned over in the conductive material depending on the applied potential; i.e., the activity is electrochemically controllable

A biocompatible needle-type glucose sensor based on platinum-electroplated carbon electrode.

Abstract: A biocompatible needle-type glucose sensor with a 3-electrode configuration was constructed. A platinum-electroplated carbon stick was used as the working electrode, Ag/AgCl as the reference electrode, and a disposable hypodermic needle made of stainless steel as the counter electrode. A Nafion membrane, an immobilized glucose oxidase (GOD) membrane, and a biocompatible membrane with diffusion-limiting effect were coated successively onto the working electrode. The sensor showed a rapid response ( 0.95).

Electrochemical measurement system having interference reduction circuit

Abstract: A system for electrically measuring certain chemical characteristics of electrically-conductive fluids, such as blood, located within a tube and subject to electrical current interference. The measurements are made by measuring the voltage potential between a reference electrode and a sensor electrode sensitive to a particular blood parameter such as pH or calcium, potassium or chloride concentration. A bypass path for the electrical current interference is provided by a pair of noise-reduction electrodes located on opposite sides of the reference and sensor electrodes and interconnected by an amplifier having a relatively low output impedance and a relatively high input impedance. The electrical current interference bypasses the signal electrodes by flowing directly into the amplifier's output terminal, such that the reference and sensor electrodes develop a potential between them that is independent of the electrical current interference.

Method and electrode for electrochemical recovery of lithium value from aqueous solution

Abstract: A novel and efficient electrochemical method is disclosed for the recovery of lithium value from an aqueous solution containing lithium ions in a relatively low concentration together with ions of various kinds of other metallic impurity elements The method comprises electrochemical selective adsorption of lithium ions from the aqueous solution on to a specific working electrode by applying a DC voltage of a relatively low DC voltage of 01-04 volt versus a saturated calomel electrode to the working electrode as the cathode opposed to a counterelectrode as the anode and then desorption of the lithium ions therefrom by applying a DC voltage of 07-12 volts versus a saturated calomel electrode to the lithium-bearing working electrode as the anode opposed to a counterelectrode as the cathode in an aqueous desorption medium containing an electrolyte such as a lithium salt At least the surface layer of the working electrode is formed from an oxide of manganese prepared by admixing a manganese compound with a limited amount of a lithium or magnesium compound, converting the mixture into oxides by a heat treatment in an oxidizing atmosphere and then removing the lithium or magnesium therefrom by leaching in an acid solution or by an electrochemical means

ANALYTE AND pH MEASURING SENSOR ASSEMBLY AND METHOD

Abstract: The sensor apparatus of the present invention includes on a nonconducting substrate (11) electrically conductive pathways (20, 22, 24) leading to at least two analyte electrodes (32, 34) and one reference electrode (36). The analyte electrodes (32, 34) each have sensitivities for both analytes but each has a membrane (48, 52) and/or electrolyte (50, 54) that favors the conversion of ionic potential to electronic potential for a different analyte. The apparatus has a fluid circuit means (68) for liquid contact between the electrodes (32, 34, 36) so that electric signals can be sent by electric circuitry (16) to an analyzing means (116). The analyzing means (116) determines the values of the analytes from simultaneously mathematical relationships.

Reversible Plating and Stripping of Sodium at Inert Electrodes in Room Temperature Chloroaluminate Molten Salts

Abstract: Sodium has been suggested as a possible anode in high energy‐density batteries using room temperature chloroaluminate molten salt electrolytes, but it cannot be used directly in typical melts because the reduction of Na+ falls beyond the negative voltage limit. When a neutral melt of 1‐methyl‐3‐ethylimidazolium chloride and aluminum chloride is buffered with , and excess protons are added, the negative voltage limit is extended to −2.4 V (vs. an melt reference electrode) and the reversible plating and stripping of sodium is observed. Compositional data from scanning electron microscopy and energy dispersive spectra (SEM/EDS) verify that a layer of sodium is deposited on the surface of Pt and W electrodes. MEI+ appears to be reduced at nearly the same potential as sodium and probably forms a protective layer on top of the sodium. These plated species are fairly stable on the electrode surface as judged by a constant rest potential over several hours, but can easily be stripped off the electrode by a positive potential scan. These characteristics suggest that sodium is a good candidate for the anode in a rechargeable battery.