Showing papers on "Reference electrode published in 1973"

Free Calcium in Serum. I. Determination with the Ion-Specific Electrode, and Factors Affecting the Results

Abstract: Free (ionic) calcium in human serum was measured with a commercially available ion-specific electrode, together with a saturated-KCl salt bridge, a saturated-calomel reference electrode, and a direct-reading electrometer. Effects of sodium, potassium, and magnesium on the electrode values for calcium were assessed and a rationale demonstrated for the use of calcium standards containing 140 mmol of NaCl, 5 mmol of KCl, and 0.55 mmol of MgCl2 per liter. Trypsin, triethanolamine, and heparin bind calcium; therefore, their use is to be avoided. Variability is greatly decreased if the serum is from a fasting subject and if the collection tube is completely filled, transported on ice, and handled anaerobically. The range for free calcium for 86 apparently healthy adults was 1.175-1.375 mmol/liter when measured at 25°C. The precision (coefficient of variation) of duplicates was 0.6%; the long-term precision ≃2.0%.

Solid state electrode

Abstract: A solid state electrode for use in determining ion concentration in an aqueous solution. The electrode comprises an electrically conductive inner element with a salt disposed on a surface portion thereof having as a cation a cation form of the element and also having an anion, a hydrophilic layer in intimate contact with the salt and including a water soluble salt of said anion and a hydrophobic layer in intimate contact with the hydrophilic layer whereby the hydrophilic layer is shielded from contact with the ion-containing aqueous solution. This electrode may function as a reference electrode as well as an electrode for identifying specific ions.

Flow-through amperometric measuring system and method

Abstract: An amperometric measuring system for measuring the concentration of glucose in solution is disclosed. This system uses the enzyme glucose oxidase immobilized on glass beads to convert a continuously drawn sample to hydrogen peroxide and gluconic acid. A flow-through amperometric cell with a small bore flow path is provided to measure the concentration of hydrogen peroxide. The cell includes a cylindrical measuring electrode which carries the sample through its relatively long narrow bore, a counter electrode and a reference electrode interposed between the measuring and counter electrodes with a differential amplifier for automatically adjusting the current between the measuring and counter electrodes to maintain the potential between the measuring and reference electrode at a predetermined value as fed to one input of the amplifier. The current from the measuring electrode is measured as an indication of the concentration of hydrogen peroxide in the solution and hence the glucose concentration.

Interpretation of some microelectrode measurements of electrical properties of cells.

Abstract: In recent years most measurements of the natural electrical activity of cells, such as action potentials and synaptic potentials, have been carried out using a micro­ electrode to record the electrical potential difference between the cell interior and a reference electrode in the surrounding saline solution. This is a sensible way to measure natural electrical activity since the potential recorded is a decent approxi­ mation to the potential across the cell membrane, and this membrane potential is usually the natural electrical activity of interest in the cell. It is well to remember that some natural electrical activity, such as that which may occur within intracellular organelles like mitochondria or sarcoplasmic reticulum, might not be simply related to the potential across the cell membrane. The mechanism of this natural electrical activity depends on the electrical param­ eters of the cell, which are measured by applying current to the cell and recording and analyzing the resulting potential change. In order to perform this analysis, it is necessary to know the spatial distribution of current flow, that is to say, the magnitude and direction of current flow, especially the amount of current that crosses the mem­ brane. While it is possible in some special cases (e.g. Hodgkin & Rushton 1) to apply current outside a cell and analyze in a reasonably unique manner where and how current is flowing across the cell membrane, it is not easy to do this in general. The problem is essentially that the membrane is a structure of very high impedance and so most of the current flows around the cell, not through it. The amount of current that crosses the membrane is only a small perturbation on the large quantity of current flowing in the extracellular solution. When current is applied inside a cell, however, all of it must flow across the cell membrane to the reference electrode outside and so the problem of analyzing the pattern of current flow across the membrane is greatly simplified. For this reason, most measurements of the electrical properties of cells use a microelectrode source of current, the current-passing microelectrode being inserted into the cell. The potential produced by this current flow is often recorded by another microelectrode inserted into the same cell, although at times a single microelectrode is used both to record potential and pass current. The original theoretical analysis of the electrical properties of cells was carried out for other experimental arrangements (Cole & Hodgkin 2, Hodgkin & Rushton 1), 65 A nn u. R ev . B io ph ys . B io en g. 1 97 3. 2: 65 -7 9. D ow nl oa de d fr om w w w .a nn ua lr ev ie w s. or g

The inadequate reference electrode, a widespread source of error in plasma probe measurements

Abstract: An analysis has been conducted on the influence of the reference electrode area on probe characteristics taken in the electron retarding range of potentials, when the reference electrode, and perhaps also the probe, is in the `blocking effect' r?gime (where probe dimensions are greater than or equal to the electron and ion mean free paths). A new and more severe criterion for sufficiency of reference electrode area is derived, and it is shown that insufficiency of reference area can lead not only to rounding of the `knee' of the probe characteristic, but can cause an extra, spurious, near-linear section to appear in the (log current against potential) characteristic near space potential, leading to the possibility of grossly inaccurate electron temperature measurements. A number of published results are cited to show that this phenomenon is in fact a frequent source of error in probe measurements.

Ammonium ion specific electrode and method therewith

Abstract: An electrode specific for ammonium ion is made by covering the surface of a monovalent cationic electrode with a membrane permeable to ammonia but impermeable to interfering cations such as sodium and potassium. A thin layer of buffer-electrolyte is trapped between the surface of the electrode and the ammonia permeable membrane. The reference electrode is placed, via a small plastic tubing, in the buffer-electrolyte trap. When this electrode device is dipped into a solution containing ammonia ion, of which there is an equilibrium concentration of ammonia, ammonia gas (dissolved in the sample solution) passes through the gas permeable membrane over the electrode to again produce ammonium ion. The latter is potentiometrically sensed by the active surface of the monovalent cationic electrode.

Photochemical generation of semiquinone intermediates at a rotating semi-transparent disc electrode

Abstract: Light from a mercury lamp shone through a semi-transparent electrode into a solution containing a mixture of anthraquinone and its corresponding hydroanthraquinone generates semiquinones inside the diffusion layer of the electrode. The semiquinone species can either be oxidized or reduced on the electrode. The rate constants for their electrochemical reactions and for their homogeneous recombination can be measured. At the potential of zero photocurrent the electrochemical rate constants for the reduction and oxidation of the semiquinone are equal. At this point the free energies for the first and second transition states in the electrochemical reduction of anthraquinone are equal. The variation of the potential of zero photocurrent with pH determines the electrochemical mechanism of the anthraquinone.

Carbon electrodes with phthalocyanine catalyst in acid medium

Abstract: The catalytic properties of polymeric phthalocyanines with Fe and Co as central atoms for the electroreduction of oxygen in 0.5–2.3m H2SO4 were studied. No noticeable dependence of the electrode potential on the concentration of H2SO4 was found. The electroactivity of the catalyst with a central Fe atom undergoes considerable deterioration under the given conditions, whereas the stability of the catalyst with a central Co atom is very good and the potential of an electrode containing 30% catalyst in the active mass is 100 mV more positive than that of an electrode with 13% platinum, both at 40 mA cm−2. The electrode performance depends markedly on the sort of carbon substrate, showing a parallelism with respect to oxygen electrodes in alkaline medium. The gold mesh current collector can be replaced by the addition of carbon black to the active layer.

Properties of the tungsten-silicon dioxide interface

Abstract: We have determined a value of 3.6 ± 0.1 eV for the WSiO2 zero-field barrier height. This value compares well with values obtained indirectly by other methods. Fitting the photoinjection data with equations from a theoretical model gives a scattering length of W electrode. A value of ∼ 17A results for an Au electrode on the same sample, indicating that the oxide properties near the gate electrode are not significantly different for W or Au electrodes. Annealing experiments on WSiO2Si structures with Au reference electrodes suggest that the amount of interface fixed charge Qss may depend on the presence of the tungsten as well as the thermal history of the interface.

Method and apparatus for measuring pitting corrosion tendencies

Abstract: A Cathode, an Anode wrapped in filter paper or other barrier to oxygen diffusion, a Reference Electrode (and optionally an Auxiliary Electrode) are placed in an aerated electrolytic liquid The open circuit potential between the Cathode and Reference Electrode is impressed upon a capacitor By means of a two-position switch an operational amplifier then causes the potential of the anode, in a circuit including the Reference Electrode, Auxiliary Electrode (or the electrode previously used as the Cathode) and an Ammeter, to become equal to the open circuit cathode-reference electrode potential impressed upon the capacitor The amplifier provides the necessary current of either polarity to achieve the equality The polarizing current flowing through the Ammeter is read and a qualitative indication of the pitting tendency is obtained

Apparatus for or selective dissolution or detection of predetermined metals

Abstract: Apparatus and methods are disclosed for the selective dissolution of a predetermined metal from, for example, a metal-metal combination. The metal or the metal-metal combination is made the working electrode of an electrolytic cell whose other electrode is electrolytically inert in the cell in use. The working electrode is held at a substantially constant electrical potential relative to a standard calomel electrode, and this potential and the pH of the electrolyte are selected such that the electrical energy passing through the cell during a selected time period is dependent on the amount of the predetermined metal electrolytically dissolved and substantially independent of any other metal which may be present.

Micro and Semimicro Determination of Thiols with Ion-Selective Electrodes*

Abstract: This paper describes the potentiometric determination of a variety of thiols. Microamounts (0.01 to 0.1 mM) are titrated with 0.01N mercuric perchlorate while semimicroamounts (0.1 to 0.5 mM) are titrated with 0.05N mercuric perchlorate. A bromide selective indicator electrode and a single-junction reference electrode are used with an expanded-scale pH meter to monitor the emf. Other indicator electrodes based on a silver sulfide matrix may also be used. The preferred solvent is acetone while ethanol andp-dioxane have limited applicability. The electrode response is slower in general than for other titrations using ion-selective electrodes, particularly for the more complex thiols and those attached to a heterocyclic ring system.

Electrical energy storage device utilizing an electrode composed of an amorphous carbon and sulfur-carbon complex

Abstract: The energy storage capacity of a carbon electrode can be increased by advantageously incorporating additive elements into the electrode by the process of initially heat-treating the carbon electrode at a temperature between 700* and 1,000* C under a partial vacuum; subsequently exposing the electrode to the vapors of the desired compound under a slightly positive pressure and at a temperature below about 1,000* C; followed by cycling the electrode alternately in a charge and discharge direction in a cell containing a fused salt electrolyte composed of the halides of alkali metals or alkaline earth metals or their mixtures.

Oxygen sensor and electrode device therefor

Abstract: AN OXYGEN SENSOR IS DESCRIBED WHICH HAS AN ELECTRODE DEVICE WITH A FIRST ELECTRODE AND A REFERENCE ELECTRODE, AND AN AQUEOUS BUFFERED SOLUTION OF AN ELECTROLYTE CONTAINING A HALIDE SALT WHICH CONTACTS THE NOBLE METAL PORTION OF THE FIRST ELECTRODE AND THE SILVER HALIDE LAYER OF THE REFERENCE ELECTRODE OF THE ELECTRODE DEVICE. THE ELECTRODE DEVICE HAS A CHEMICALLY-BIASED OXYGENSENSING ELECTRODE WITH A CLOSED-END TUBE, THE TUBE HAVING A PORTION OF A NOBLE METAL SELECTED FROM THE CLASS CONSISTING OF PALLADIUM AND PALLADIUM ALLOYS, A RESERVOIR FOR HYDROGEN CONNECTED TO THE OPPOSITE END OF THE TUBE, AND A HYDROGEN GAS SOURCE CONTAINED WITHIN AT LEAST THE RESERVOIR; A LAYER OF ELECTRICAL INSULATION COVERING AT LEAST PARTIALLY THE TUBE LEAVING THE NOBLE METAL PORTION AT LEAST PARTIALLY EXPOSED, AND A REFERENCE ELECTRODE INSULATED ELECTRICALLY FROM THE NOBLE METAL PORTION, THE REFERENCE ELECTRODE CONSISTING OF SILVER WITH AT LEAST A PARTIAL LAYER OF SILVER HALIDE THEREON.

Hydrogen cyanide sensing cell

Abstract: An improved gas-sensing electrochemical cell for measuring hydrogen cyanide gas in a sample solution. The cell comprises a potentiometric silver ion-sensitive electrode and a reference electrode, both in contact with an internal standard solution comprising an aqueous solution of an argento cyanide complex. A hydrophobic hydrogen cyanide gas-permeable membrane separates the sample solution from the internal solution.

Reactor vessel lining testing method and apparatus

Abstract: Protectively lined reactor vessels may be monitored for lining damage by measuring the potential which develops between a tantalum reference electrode and any exposed steel resulting from lining damage. The reference electrode is preferably tantalum which is insulated in part to insure that it is not grounded to the vessel. The reference electrode is connected to a voltmeter which in turn is connected to the conductive reactor body to complete the passive DC electrical circuit. A background potential is normally observed even in a vessel having no lining damage. The presence of damage in the lining causes a substantial increase in the observed potential.