Membrane-covered oxygen electrodes

Jensen, O.J.; Jacobsen, Torben; Thomsen, Kay

doi:10.1016/s0022-0728(78)80301-5

Cited by 30 publications

(15 citation statements)

References 12 publications

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“…104 The best model is two dimensional where linear diffusion takes place in the membrane and radial diffusion to the microelectrode takes place within the electrolyte solution behind the membrane. 105 …”

Section: 4 Oxygenmentioning

confidence: 99%

A review of flux considerations for in vivo neurochemical measurements

Paul

Stenken

2015

Analyst

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The mass transport or flux of neurochemicals in the brain and how this flux affects chemical measurements and their interpretation is reviewed. For all endogenous neurochemicals found in the brain, the flux of each of these neurochemicals exists between sources that produce them and the sites that consume them all within μm distances. Principles of convective-diffusion are reviewed with a significant emphasis on the tortuous paths and discrete point sources and sinks. The fundamentals of the primary methods of detection, microelectrodes and microdialysis sampling of brain neurochemicals are included in the review. Special attention is paid to the change in the natural flux of the neurochemicals caused by implantation and consumption at microelectrodes and uptake by microdialysis. The detection of oxygen, nitric oxide, glucose, lactate, and glutamate, and catecholamines by both methods are examined and where possible the two techniques (electrochemical vs. microdialysis) are compared. Non-invasive imaging methods: magnetic resonance, isotopic fluorine MRI, electron paramagnetic resonance, and positron emission tomography are also used for different measurements of the above-mentioned solutes and these are briefly reviewed. Although more sophisticated, the imaging techniques are unable to track neurochemical flux on short time scales, and lack spatial resolution. Where possible, determinations of flux using imaging are compared to the more classical techniques of microdialysis and microelectrodes.

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Section: 4 Oxygenmentioning

confidence: 99%

A review of flux considerations for in vivo neurochemical measurements

Paul

Stenken

2015

Analyst

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“…Planar diffusion within the membrane coupled with radial diffusion within the electrolyte was the simplifying assumption of Jensen et. al 11 in the derivation of an approximate expression for the intensitity current. So we can expect a better agreement of the Jensen et al approach with the rigorous solution for systems with low z e (when one-dimensional reduction of the flux within the electrolyte layer is less crude) and with thin and more impermeable membranes (when the flux lines come closer to the normal).…”

Section: Index Of Edge Effect Contributionmentioning

confidence: 99%

“…Mathematically, the steady-state inlaid electrode system in a multilayered medium had been previously modelled using a one-dimensional approach [5][6][7] (unable to account for the "edgeeffect" [8][9][10] ) or a "mixed" (radial/axial) approach 11 . All such attempts are restricted to gas sample or thoroughly stirred liquid sample sensors.…”

Section: Introductionmentioning

confidence: 99%

“…All such attempts are restricted to gas sample or thoroughly stirred liquid sample sensors. Electrochemical permeability determinations have been carried out through various methods usually relying on onedimensional models 12-15 . In the "axisymmetric" or "cylindrical" model, 3 horizontal layers (electrolyte, membrane and sample solution) extend up to infinity parallel to the disk and the coplanar insulator around it 11,16,17 . Numerical simulation of the currents either through finite differences or finite elements 18,19 involve considerable computational effort.…”

Section: Introductionmentioning

confidence: 99%

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Behaviour of the current in a membrane-covered disc microelectrode under steady-state conditions

Galceran¹,

Salvador²,

Puy³

et al. 1996

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The inlaid disc electrode covered with a membrane can be modelled as a system with axial symmetry containing several parallel layers with different permeabilities. A recent solution of the steady state under diffusion limited conditions of an electroactive species in such a system is implemented with Mathematica and the code for the exact solution and an approximation is provided. Computation of the theoretical intensity current becomes an easy and fast procedure, capable of being implemented on any personal computer or workstation. The effect of the membrane permeability, the thickness of the membrane, the electrode radius and the electrolyte layer thickness on the intensity current are analysed. We define an index of edgeeffect contribution of each layer to the overall flux, providing their formulae together with the physical interpretation. For many sets of parameters, the edge-effect is responsible for an important contribution of the radial diffusion within the electrolyte and membrane. More accurate determination of the permeabilities of the different media is now possible experimentally, as the functional dependence of the current on the physical parameters is readily available for fitting procedures.

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“…This continuity, as well as continuity of oxygen flux through the layer interfaces, is expressed by conditions [6] and [7]. From the solution to the set of equations [1] to [8] obtained by the standard method of Laplace transform according to Jaeger (14) one can find an expression for the intensity of oxygen flux toward the cathode by using N(t) = -kE ~ [9] Or I r=r 0 current response of the sensor is then The transient given by…”

Section: Theoreticalmentioning

confidence: 99%

Transient Diffusion of Oxygen Through the Three Spherical Layers of the Clark Oxygen Sensor

Vacek

Linek

Sinkule

1986

J. Electrochem. Soc.

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A general theoretical description of the transient behavior of the amperometric Clark oxygen electrode based upon a one-dimensional spherical model is given in analytical form and compared with existing data. The resulting expressions relate transient characteristics of the sensor to transport properties of the three layers which determine the rate of oxygen diffusion from ambient flowing liquid or semisolid tissue to the surface of the sensor cathode. Criteria are presented by which the errors associated with earlier, less comprehensive models may be estimated. The effects of variation in hemispherical electrode radius are investigated for sensors exhibiting typical transport characteristics. Decreasing this radius is predicted to lead to complete suppression of sensor sensitivity to flow rate, while the dependence of transient characteristics upon flow rate is only partially diminished. Contrary to what might be believed on the basis of intuition, this model predicts that the response time for a typical electrode will decrease with decreasing electrode radius only until the radius approaches 7 ~m; thereafter, further reductions in electrode radius are shown to cause the response time to increase.Oxygen probes of the Clark type usually consist of noble metal or Ag cathode and of reference Ag/AgC1 or Ag/Ag20 anode immersed in aqueous solution of suitable inorganic electrolyte. The electrode system is separated from a medium measured by a thin plastic membrane permeable to oxygen. These oxygen sensors are finding increasingly wide-spread use in dynamic measurements. Evaluation of the data obtained requires a knowledge of transient characteristics of the probe. The present state of knowledge on dynamic behavior of oxygen probes has been summarized in recent reviews (1, 2).When electrochemical conditions are chosen so as to allow the sensor to operate in the limiting diffusion current region with constant, four electron overall stoichiometry of electrochemical reduction of oxygen at the cathode, the probe dynamics is determined by rates of oxygen transport through the following three layers: (i) a thin layer of the medium in front of the probe membrane, i.e., the concentration boundary layer of the medium, (ii) the membrane, and (iii) the electrolyte layer between cathode and the membrane. Steady-state solutions have been published for two-layer spherical models considering either the membrane and the electrolyte layer (3, 15) or the membrane and the film layer (4,5,16,17). Grunewald (6) has solved the transient characteristics of one-layer spherical model; for the two layer model, he solved the response to a sudden concentration change within a film of infinite thickness. Lee et al. (5) have described unsteady solution based on two-layer spherical model for the case where the probe is switched on after its equilibration with the surrounding medium, Thus, the transient characteristics for the two-layer model for the step change in the concentration of oxygen were not dealt with by the authors (5, 6). The solution de...

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Membrane-covered oxygen electrodes

Cited by 30 publications

References 12 publications

A review of flux considerations for in vivo neurochemical measurements

A review of flux considerations for in vivo neurochemical measurements

Behaviour of the current in a membrane-covered disc microelectrode under steady-state conditions

Transient Diffusion of Oxygen Through the Three Spherical Layers of the Clark Oxygen Sensor

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