Showing papers on "Reference electrode published in 1984"

Sensor electrode systems

Abstract: This specification discloses sensor electrodes, and their combination with reference electrodes; the manufacture of such electrodes; apparatus utilising such electrodes; and electrical circuitry into which such electrodes can be incorporated, specifically the establishment of certain design criteria in the production of such electrodes for lay, or clinic, use. The electrodes can be used in an invasive probe (i.e. one which enters body tissue to contact a bodyfluid such as whole blood or subcutaneous tissue fluid) or as part of an external test upon a withdrawn sample (using a syringe) or upon an expressed sample (e.g. using a needle-prick device). In the specification claims, sensor means for selective detection, measurement or monitoring of a given dissolved substrate in a mixture of dissolved substrates, comprising:- (a) an area 4 of first electrode material comprising an enzyme catalytic of the said substrate and a mediator compound to transfer charge to the electrode when the enzyme is catalytically active, adjacent to but non-contiguous with; (b) an area 5 of reference electrode material; both electrodes being of small dimension, and extending as or supported on an elongate member to facilitate manipulation before or during contact with live tissue or a small withdrawn sample of body fluid.

Ion concentration measuring apparatus

Abstract: An apparatus for measuring a concentration of a specific ion contained in a test liquid held in a container with the aid of a reference electrode and an ion sensitive field effect transistor having a gate portion selectively sensitive to the specific ion, including a series circuit of a reference resistor and a constant voltage supply source connected across drain and source of the ion sensitive field effect transistor, a potential control circuit having inputs connected across the reference resistor to detect a potential difference across the reference resistor for controlling a source or drain potential of the ion sensitive field effect transistor in such a manner that the potential difference remains at a predetermined value and a voltmeter for measuring the source or drain potential as a measure of the ion concentration.

Electrocatalysis with a Glucose-Oxidase-immobilized Graphite Electrode

Abstract: Glucose oxidase was immobilized on the surface of a graphite electrode by irreversible adsorption. An electrocatalytic steady-state current for the oxidation of D-glucose was observed using this electrode in the presence of p-benzoquinone as an electron transfer mediator. The electrocatalytic current at 0.5 V vs. SCE was analyzed as a function of the concentrations of D-glucose and p-benzoquinone, and the maximum current, Ismax, and the Michaelis constants (K1 and K2 for D-glucose and p-benzoquinone, respectively) of the electrocatalysis were determined. The dependence of the current on the electrode potential, pH, and temperature was also investigated. The results indicate that the kinetics of the immobilized enzyme are essentially the same as those of the enzyme in the solubilized state. The effect of various electron transfer mediators on the electrocatalytic current was also examined and evaluated in terms of Ismax, K1, and K2 values.

Electrode system for an electro-chemical sensor for measuring vapor concentrations

Abstract: An electrode system for an electrochemical sensor has a plurality of electrically conductive sensing segments isolated from each other and mounted on a support substrate formed from a chemically inert encapsulation material. The sensing segments are unencapsulated and are each coated with respective ones of ion conducting sensing materials to characterize each of the segments except for one of the segments which is uncoated and is arranged to be used as a reference electrode. The outer surface area of the sensing materials and the reference electrode is coated with a layer of a nonaqueous electrolyte which serves as a sorption/desorption medium. The electrolyte, in turn, is covered by a semipermeable thin film membrane secured at its peripheral edge by an O-ring to the support to form a fluid seal. Electrically conductive leads are connected to respective ones of the sensing surfaces, and a temperature measuring device is provided in the electrode structure for temperature compensation.

Method and device for compensating temperature-dependent characteristic changes in ion-sensitive fet transducer

Abstract: An electrical circuitry for use in the measurement of the activity of ions in an electrolyte solution carried out by the use of an ion-sensitive field-effect transistor transducer having a gate or ion sensitive layer, a source and a drain. The measurement is carried out by adjusting the drain current flowing through the field-effect transistor to a predetermined value such that the temperature dependency of the electroconductivity of the channel of the transistor becomes equal to the sum of the temperature dependency of the potential at an interface between a reference electrode and the electrolyte solution and the temperature dependency of the potential at an interface between the ion-sensitive layer and the electrolyte solution.

Electrochemical sensor capable of determining hydrogen peroxide concentration and analyzer using the same

Abstract: A urea-determining sensor and a glucose-determining sensor are arranged to face a single passage through which a sample flows The urea sensor combines a membrane of immobilized urease with an ammonium ion-selective electrode The glucose sensor consists of a layer of immobilized glucose oxidase and a polarographic electrode having a hydrogen peroxide-permeable layer The latter sensor incorporates a work electrode and a counter electrode, and determines the concentration of hydrogen peroxide that permeates therethrough from the intensity of electric current that flows between the two electrodes The counter electrode of the glucose sensor is formed of metallic palladium The specific counter electrode material eliminates the problem of silver dissolution into the flow passage and extends the life of the urea sensor

Electrochemical properties of adriamycin adsorbed on a mercury electrode surface.

Abstract: The electrochemical behavior of adriamycin has been studied by means of cyclic d.c. and a.c. voltammetry with a hanging mercury drop electrode, quinizarin being used as a model compound. Both adriamycin and quinizarin are strongly adsorbed on the mercury electrode with their aromatic ring planes oriented parallel to the electrode surface, and give two sets of reduction waves. The first wave, due to the quinone moieties of the adsorbed adriamycin and quinizarin, has been explained on terms of a two-step one-electron surface redox reaction. The formal standard redox potentials, semiquinone formation constants, and charge transfer rate constants of the surface redox reaction of the quinone moieties have been determined. Although the reduced form of adriamycin is not very stable chemically, it is converted to a stable and electrochemically active form for a few minutes at pH 4.54. The second wave appearing at more negative potential would be due to a kinetic or catalytic process.

Bioelectrochemical assay electrode

Abstract: An electrode is, at least in part made from a material (X) having one-dimensional electrical conduction properties. The material X is conveniently an organic conductor, and preferably a derivative of 7,7,8,8 tetracyano p-quinodimethane, especially in combination with one of the following ions or a salt thereof; Cu(di-pyridylamine), tetrathiafulvalene, ferricinium, triethylammonium or quinolinium. It may be a single crystal or packed into the cavity of a cavity electrode. The electrode may and comprise, at least at an external surface thereof the combination of an enzyme and a mediator compound which transfers electrons to the electrode when the enzyme is catalytically active. The additional material may be NAD /NADH couple, an oxidised/reduced flavin couple, or choline oxidase.

Surface-enhanced Raman scattering of piperidine. The effect of electrode potential on intensity

Abstract: Etude du comportement du spectre Raman d'excitation de surface (SERS) de la piperidine soumise a l'effet d'un potentiel applique a une electrode d'argent; observation de la structure de l'interface piperidine-electrode. Proposition d'interpretation des changements de l'intensite de quelques bandes par un modele de mecanique quantique

Liquid chromatograph with electrochemical detector and method

Abstract: An improved apparatus for electrochemically analyzing a sample in solution is described. The apparatus comprises an electrochemical detector comprising a plurality of electrochemically isolated flow cells arranged in series so as to define at least one flow path. Each of the electrochemical flow cells in turn comprises at least one working electrode, at least one reference electrode, and at least one counter electrode. Electrical potentials are applied to the various working electrodes so that the sample solution is cyclically subjected to oxidation and reduction conditions whereby selected substances contained in the sample solution may be electrically screaned or modified prior to detection and measurement on a downstream sensing electrode.

First report of intramyocardial pH in man: I. Methodology and initial results.

Abstract: Continuous in vivo measurements of intramyocardial pH (MpH) have not been previously obtained in man. To achieve this goal, we developed in our laboratory a new, steel-jacketed, glass electrode, and circumvented temperature-related problems by recording the output in millivolts along with the adjacent myocardial temperature. A computer program was devised to calculate MpH in accordance with the Nernst equation. The need in this system for a remote, subcutaneous, reference electrode prompted two sets of experiments. The first set of experiments demonstrated in vitro that the adverse effect of varying the temperature of the reference electrode on the calibration of the pH electrode could be avoided if the reference electrode was placed in a potassium chloride (KCl) solution outside the body and connected to the subcutaneous tissues with a salt bridge. The second set of experiments, which were conducted in vivo in dogs, demonstrated that MpH measurements made with the reference electrode in the limb were not affected by ischemic electrocardiographic changes. This system was then used successfully in 10 patients undergoing coronary artery bypass surgery. Reliable, reproducible, and uniform changes were observed. Baseline MpH prior to revascularization was 6.81 +/- 0.07. Myocardial protection with cold K+ cardioplegia resulted in a significant rise in MpH to 7.45 +/- 0.06. Throughout the period of cross-clamping, MpH remained high. After revascularization and discontinuation of cardiopulmonary bypass, MpH stabilized at 6.93 +/- 0.04.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrode Resistance of Metal Hydride in Alkaline Aqueous Solution

Abstract: The electrode resistance of metal hydride in constant-current electrolysis is investigated. It is found that the diffusion of hydrogen in the electrode is the rate-determining step in the reaction and is the dominant cause of the electrode resistance. The activity of the electrode, corresponding to the reaction rate, is determined by the effective surface area and the diffusion coefficient of hydrogen in the bulk of the electrode. Some parameters concerning the electrode kinetics are estimated. TiMn1.5 is an excellent electrode material for a secondary battery with high current and energy densities.

Acidity constant of hydrofluoric acid

Abstract: A detailed experimental investigation of the association (acidity) constant of hydrofluoric acid has been made at 25°C in sodium perchlorate media at ionic strengths between 0.01 and 0.5M. Results were obtained by potentiometry using a fluoride ion-selective electrode in conjunction with three types of reference electrode, all involving cells with liquid junction. After careful consideration of possible errors in the present results and a critical study of the literature, a zero ionic strength pK a o (HF) value of 3.18±0.02 is recommended until existing contradictions can be resolved.

Solid Reference Electrode of SO 2 Sensor Using β-Alumina Solid Electrolyte

Abstract: Deux electrodes de reference: Au+Au 2 Na et (β+β'')-alumine sont proposees pour l'analyseur

Electrochemical gas sensor

Abstract: An electrochemical gas sensor, particularly suitable for detecting a gas such as H₂S, includes an electrochemical de­ tection cell which has a reference electrode (80), a sensing electrode (90) and a counter eiectrode (81). The counter elec­ trode (81) is composed of carbon. The sensing electrode may be composed of gold or platinum and the reference electrode may be composed of platinum. Circuitry (108, 110-115, 117) is provided to supply voltage to the electrodes, the sensing elec­ trode (90) bias can be held below 300 mv., with respect to the reference electrode (80). The agent H₂S can be readily de­ tected when the bias is about 250 mv. The sensor is associated with signal processing circuitry (120-128, 130-135) which pro­ duce audible (31) and visual outputs (160, 166). A nonaqueous electrolyte is provided. The electrolyte may be composed of n-­ methyl-2-pyrrolidone C₅H₉NO and one of conductive compati­ ble salts, such as tetrabutyl ammonium tetrafluoroborate [CH₃(CH₂)₃]₄NBF₄. The invention overcomes the problem of shelf life arising from evaporation of the electrolyte, tempera­ ture range arising from the electrolyte freezing and cost arising from expensive electrode materials.

Method of operating a self cleaning electrochemical detector

Abstract: An improved electrochemical cell and detector which is especially suited for analysis of rapidly changing flowing streams such as found in high performance liquid chromatography is disclosed. A uniquely designed jet made of microbore drawn capillary tubing permits the construction of a cell for very low flow rates that still retains true wall-jet hydrodynamics. The invention prevents changes in cell response in time by periodically cleaning a working electrode in a novel way. Cleaning and detection are both accomplished on a time scale much shorter than the fastest liquid chromatograph peaks by means of a unique three electrode cell design utilizing a small diameter, low capacitance, metal working electrode situated close to a reference electrode. Cleaning is accomplished by means of a nonsquare wave periodic waveform which is effective in cleaning a wide variety of contaminants through the oxidation and reduction of the working electrode and/or solvent prior to application of one or more working potentials while providing a stable, reproducible detector. The detector thus provides improvements in both sensitivity and bandwidth over the prior art.

Oxygen sensor element

Abstract: A measuring electrode is mounted on one side surface of a solid electrolyte, while a reference electrode is mounted on a separate solid electrolyte and disposed so as to face the opposite side surface of said one solid electrolyte across a gap.

Electrode arrangement for the electrochemical analysis of the electrolytic component of a liquid

Abstract: The electrode arrangement for the electrochemical analysis of electrolytic components of a liquid, in particular blood or urine, has a base body 7 of insulating material and a sample chamber 11, externally accessible via a loading aperture, in the base body 7 for receiving the liquid to be analysed. Attached to the base body is at least one measuring electrode 21 which is selective for a predetermined ion species in the liquid to be analysed, and also a reference electrode 19. The electrode arrangement is designed as a disposable part, the loading aperture being sealed by the manufacturer with a removable closure part 45 which forms a sealed hollow chamber together with the sample chamber. Introduced into the sealed hollow chamber by the manufacturer is a standard electrolyte solution which contains the predetermined ion species with a predetermined activity and which wets the measuring electrode 21 and the reference electrode 19 and consequently preconditions them. To carry out the actual analytical measurement, the closure part 45 is removed and the standard electrolyte solution is removed together with an absorbent elastic cushion which is mounted on the closure part 45 and impregnated with the standard electrolyte solution. According to a second main feature, the invention proposes an electrode arrangement using a copper/copper sulphate system, in particular for the reference electrode, which is notable for a rapid and stable potential setting, accompanied by simple and cheap manufacture of the disposable part.

Ion measuring device with self-contained storage of standardization solution

Abstract: An ion measuring device (pH meter) is adapted to store and discharge standardizing solution, as well as to provide measurements of the hydrogen or other ion concentrations of unknown samples; the device including a working electrode of known construction and a reference electrode adjacent to the working electrode; and further including at least one storage reservoir for containing a standardizing solution, and a measuring or standardizing chamber located at the lower end of the reservoir with means, preferably in the form of a valve, for permitting communication between the reservoir and standardizing chamber such that standardization and calibration can be carried out.

Heme protein immobilized electrode and its use

Abstract: An electrical conducting solid electrode on the surface of which cytochrome c3 is immobilized in an amount ranging from 20%-100% of the monolayer coverage, said electrode thereby provided with the electrocatalytic capability of the direct four-electron reduction of dioxygen to water, and its uses.

Sodium ion-selective electrode based on crown ether-phosphotungstic acid precipitates

Abstract: A sodium ion-selective PVC membrane electrode based on 12-crown-4-phosphotungstic acid precipitates was prepared with dipentyl phthalate as a plasticiser. The electrode gave a linear response with a Nernstian slope (59 mV decade–1) within the concentration range 10–1–10–4M NaCl. The electrode exhibited comparatively good selectivity for sodium with respect to other alkali and alkaline earth metal ions. The effects of the pH of the testing solution, the concentration of the internal solution in the electrode and the composition of the membrane are discussed.

Method of and system for real time differential pulse detection

Abstract: An electrochemical detection cell which includes, in the order named, a stack of components constituted by a first membrane, an electrode carrier having reference and counter electrodes thereon, a membrane support, an electrode carrier having a sensing electrode thereon, and a permselective membrane. Whatman filter papers are positioned between the sensing electrode and both the counter electrode and reference electrode, these being positionable in a central rectangular opening of the membrane support. The cell allows air or gas ambient to address the membranes and effects application of an electrolyte to space between the electrodes by, for example, a wick which extends between an electrolyte-containing reservoir and the Whatman filter papers. A system for detecting a gaseous agent uses the aforementioned detection cell coupled with circuitry capable of applying a fixed DC voltage bias to the reference electrode and superimposing a train of DC voltage pulses on the fixed bias. Further circuitry is coupled to and responsive to signals from the sensing electrode. This circuitry determines the difference between the sensing electrode signal at the end of each pulse minus that just before each pulse. The difference is proportional to the concentration of the test gas in the atmosphere adjacent to the sensor, and is a more specific and sensitive indication of the test gas concentration than prior art sensors.