CA1074867A - Apparatus for electrolytically determining a species in a fluid - Google Patents
Apparatus for electrolytically determining a species in a fluidInfo
- Publication number
- CA1074867A CA1074867A CA288,245A CA288245A CA1074867A CA 1074867 A CA1074867 A CA 1074867A CA 288245 A CA288245 A CA 288245A CA 1074867 A CA1074867 A CA 1074867A
- Authority
- CA
- Canada
- Prior art keywords
- electrode
- medium
- species
- fluid
- barrier
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/406—Cells and probes with solid electrolytes
- G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
- G01N27/4075—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
Abstract
ABSTRACT OF THE DISCLOSURE
An electrolytic cell for measuring the concentration of a species such as oxygen is constructed by depositing closely spaced interleaved inert electrode surfaces on the surface of an insulating substrate and covering the electrode surfaces with a thin film of electrolyte and permeable membrane. The electrolyte is selected so that the species being measured is generated at one electrode surface and consumed at the other with no net reaction in the electrolyte. Alternatively, a cylindrical configuration may be formed by closely winding two thin electrode wires about a cylindrical base and covering with an electrolyte and a membrane.
An electrolytic cell for measuring the concentration of a species such as oxygen is constructed by depositing closely spaced interleaved inert electrode surfaces on the surface of an insulating substrate and covering the electrode surfaces with a thin film of electrolyte and permeable membrane. The electrolyte is selected so that the species being measured is generated at one electrode surface and consumed at the other with no net reaction in the electrolyte. Alternatively, a cylindrical configuration may be formed by closely winding two thin electrode wires about a cylindrical base and covering with an electrolyte and a membrane.
Description
~L1174~367 This invention relates to electrochemical apparatus and more particularly to improved devices for electrically measuring the concentra-tion of electrochemically active species in fluids.
The term '~fluids" as used herein is intended to include gases, liquids, vapors and mixtures thereof. Heretoore, in the determination of the concentration in ~luids of an electrochemically active species ~a sub- -stance which is capable of ~eing either reduce~ or oxidized at an electrode), electrochemical devices have been used in which an electrical characteristic of the species is measured and correlated with the concentration. Polaro-graphic devices, for example, have been used measuring the diffusion-limited current at a characteristic potential at which such a specles is electroreacted, such current being proportional to the species concentration.
An improvement on the basic polarographic apparatus is the well known Clark cell described in United States patent 2,913,386 issued November 17, 1959.
~he apparatus disclosed in that patent utili~es a dual electrode structure immersed in an electrolyte and encased at least in part in a membrane which is permeable to a predetermined species, for instance, gaseous oxygen.
Typically, when used for oxygen analysis the cathode of a Clark apparatus is formed of platinum or gold and is located closely adjacent the ~embrane;
the anode may be formed of silver in some cases and in some structures is made of lead and thé electrolyte is usually an aqueous alkali halide solu-tion. In operation such a device when used to measure oxygen has a mbmbrane which is permeable to oxygen so that the oxygen in the fluid being tested, which is outside the membrane, permeates the membrane and is presumably re-i duced at the cathode to water in accordance with the overall equation , 2H~ ~ 1/2 2 ~ 2e ~ H20 -It will be apparent that the Clark cell is intended to reduce completely the oxygen permeating the mem~rane. The current (2e) necessary to effect this reduction is a measurement of the oxygen concentration in the test fluid.
In determining oxygen concentration this device typically can employ the ~ silver-silver chloride anode with a potassium chloride electrolytic solution .
,, - 1- ~ ~
74~36i7 In that case the anode reaction would be Ag + Cl -~ AgCl ~ e Where a lead electrode is used for the anode the reaction would be Pb -~ Pb -~ 2e While devices of the type described above, normally referred to as Clark cells, have proved satisfactory for many purposes, several problems may be encountered in certain applications. Some of the disadvantages which are inherent in the Clark type cell arise from the fact that the reactions ~wh`ich give rise to the measured current irreversibly change the internal solution composition. This change may in some cases alter the pH of the electrolyte in time, and result in the physical consumption of the anode. Thus, there may be required either a means for maintaining the pH of the electrolyte as by use of a buffer and/or the supply of sufficient electrode material and electrolyte to withstand the changes without significantly altering the system properties.
Certain of the other problems encountered with the Clark system and another prior art system are more readily understood by reference to the accompanying drawings, in which:
Figure 1 is a graphical representation of the concentration gradient across the selectively permeable membrane in Clark type prior art devices;
Figure 2 is a graphical representation of the concentration gradient through the electrolyte-electrode structure of the prior art type of device ; disclosed in United~tate-s~patent 3,260~656 issued on July 12, 1966 to James . Ross.
Figure 3 is an elevated ~iew of a portion of the cell of the present invention including the electrode surfaces.
Figure 4 is a cross-section view of the cell.
Figure 5 is a graphical representation of the flux paths through the permeable membrane.
'~ 30 Figure 6 is a cross-section view of a cell similar to Figure 4 but .
The term '~fluids" as used herein is intended to include gases, liquids, vapors and mixtures thereof. Heretoore, in the determination of the concentration in ~luids of an electrochemically active species ~a sub- -stance which is capable of ~eing either reduce~ or oxidized at an electrode), electrochemical devices have been used in which an electrical characteristic of the species is measured and correlated with the concentration. Polaro-graphic devices, for example, have been used measuring the diffusion-limited current at a characteristic potential at which such a specles is electroreacted, such current being proportional to the species concentration.
An improvement on the basic polarographic apparatus is the well known Clark cell described in United States patent 2,913,386 issued November 17, 1959.
~he apparatus disclosed in that patent utili~es a dual electrode structure immersed in an electrolyte and encased at least in part in a membrane which is permeable to a predetermined species, for instance, gaseous oxygen.
Typically, when used for oxygen analysis the cathode of a Clark apparatus is formed of platinum or gold and is located closely adjacent the ~embrane;
the anode may be formed of silver in some cases and in some structures is made of lead and thé electrolyte is usually an aqueous alkali halide solu-tion. In operation such a device when used to measure oxygen has a mbmbrane which is permeable to oxygen so that the oxygen in the fluid being tested, which is outside the membrane, permeates the membrane and is presumably re-i duced at the cathode to water in accordance with the overall equation , 2H~ ~ 1/2 2 ~ 2e ~ H20 -It will be apparent that the Clark cell is intended to reduce completely the oxygen permeating the mem~rane. The current (2e) necessary to effect this reduction is a measurement of the oxygen concentration in the test fluid.
In determining oxygen concentration this device typically can employ the ~ silver-silver chloride anode with a potassium chloride electrolytic solution .
,, - 1- ~ ~
74~36i7 In that case the anode reaction would be Ag + Cl -~ AgCl ~ e Where a lead electrode is used for the anode the reaction would be Pb -~ Pb -~ 2e While devices of the type described above, normally referred to as Clark cells, have proved satisfactory for many purposes, several problems may be encountered in certain applications. Some of the disadvantages which are inherent in the Clark type cell arise from the fact that the reactions ~wh`ich give rise to the measured current irreversibly change the internal solution composition. This change may in some cases alter the pH of the electrolyte in time, and result in the physical consumption of the anode. Thus, there may be required either a means for maintaining the pH of the electrolyte as by use of a buffer and/or the supply of sufficient electrode material and electrolyte to withstand the changes without significantly altering the system properties.
Certain of the other problems encountered with the Clark system and another prior art system are more readily understood by reference to the accompanying drawings, in which:
Figure 1 is a graphical representation of the concentration gradient across the selectively permeable membrane in Clark type prior art devices;
Figure 2 is a graphical representation of the concentration gradient through the electrolyte-electrode structure of the prior art type of device ; disclosed in United~tate-s~patent 3,260~656 issued on July 12, 1966 to James . Ross.
Figure 3 is an elevated ~iew of a portion of the cell of the present invention including the electrode surfaces.
Figure 4 is a cross-section view of the cell.
Figure 5 is a graphical representation of the flux paths through the permeable membrane.
'~ 30 Figure 6 is a cross-section view of a cell similar to Figure 4 but .
-2- ~
, ,,.,. ... j.. , ~74~7 with the inclusion of a third electrode Figure 7 is a cross-section view of another form of cell showing the use of two electrodes.
In Figure 1, the ordinate 60 is the scale from zero of the relative fugacity of oxygen~ and the abscissa represents the distance from ~he cathode-membrane interface toward a test fluid. The position of the cathode-membrane interface (neglecting any small displacement between the two), is at line 60. Line 62, parallel to the ordinate, then represents the membrane-test fluid interface. The distance be~ween lines 60~and 62 is representative of the membrane thickness. Now it may be assumed that the concentration of oxygen in the test fluid adjacent to the outer surface of the mem~rane is con-stant, as shown by the horizontal portion of the broken line 6~, and that the consumption of oxygen at the cathode is complete so that the concentra-tion of oxygen at the cathode-membrane interface is substant~ally zero.
Under such circumstances the concentration gradient, represented by the re-` mainder of broken line 64, across the membrane is approximately linear and its slope is an inverse function of the m~mbrane thickness.
However, during actual operation of the device, as oxygen is con-sumed at the cathode, there is a continual flow of the gas from the test , 20 fluid through the membrane to replenish the oxygen supply being consumed or reduced. If the oxygen in the test fluid adjacent to the outer surface of the membrane is not continually replenished so as to be maintained at a ccnstant level, the concentration gradient will then extend out into the test fluid, and its slope will become non-linear and reduced as shown at broken line 66 in Figure 1~ d~e to the local depletion o~ oxygen in a layer shown between lines 62 and 68. With continued operation of the device and no replenishment of oxygen, the local depletion layer will continue to expand further out into the test fluid, distorting the concentration gradient more and more. The distortion of the concentration gradient reduces the ~:
3Q measu~ement sensitivity and change the mass flow rate of oxygen through the ~- .
,, ~
' ~3~
,. .
, . . . , , : . :
~'74~;7 membrane to the cathode, making measurement uncertain and even spurious over a period of time. In order to avoid such occurrence, seVeral means are customarily provided to minimize the extension of the depletion layer into the sample. A minimum fluid flow past the membrane-fluid interface is established, as for instance by stirring, and/or a relatively low permeability membrane may be used perhaps in combination with an inert spaeer positioned between the cathode and the membrane thereby increasing the thickness o~ the electrolyte layer, lessening the flux of the consumed species and minimizing the establishment of the depletion layer in the test fluid.
Further, i the fluid under measurement is a minute sample to which access is restricted, as is frequently the case with clinical samples of biological fluids or cells, depletion will continue until all of the oxygen is consumed. If the consumed oxygen is not or cannot be readily renewed, the measurements in a short time become inconclusive. The input ~low rate of the oxygen is often controlled by providing a relatively thick membrane which, however, acts to slow the response time of the device ~o changes in the oxygen concentration in the test fluid and lessens the magnitude of the signal current.
Further, it is common for the outer surface of the membrane, at 20 line 62, to become fouled to some extent while in use. This problem is particularly acute in applications where the sample is heavily laden with algae~ bacterial growth, or particulate. The additional impedance to oxygen . .
flux presented by the fouling causes a diminution of the sensor signal and renders the measurement inconclusive. Wipers to clean the interface, in com-bination with frequent replacement of the membranes, have been used to minimize this problem.
Some of the above mentioned disadvantages of the Clark type electrode cell are avoided by apparatus of the type described in United States patent : .
, ,,.,. ... j.. , ~74~7 with the inclusion of a third electrode Figure 7 is a cross-section view of another form of cell showing the use of two electrodes.
In Figure 1, the ordinate 60 is the scale from zero of the relative fugacity of oxygen~ and the abscissa represents the distance from ~he cathode-membrane interface toward a test fluid. The position of the cathode-membrane interface (neglecting any small displacement between the two), is at line 60. Line 62, parallel to the ordinate, then represents the membrane-test fluid interface. The distance be~ween lines 60~and 62 is representative of the membrane thickness. Now it may be assumed that the concentration of oxygen in the test fluid adjacent to the outer surface of the mem~rane is con-stant, as shown by the horizontal portion of the broken line 6~, and that the consumption of oxygen at the cathode is complete so that the concentra-tion of oxygen at the cathode-membrane interface is substant~ally zero.
Under such circumstances the concentration gradient, represented by the re-` mainder of broken line 64, across the membrane is approximately linear and its slope is an inverse function of the m~mbrane thickness.
However, during actual operation of the device, as oxygen is con-sumed at the cathode, there is a continual flow of the gas from the test , 20 fluid through the membrane to replenish the oxygen supply being consumed or reduced. If the oxygen in the test fluid adjacent to the outer surface of the membrane is not continually replenished so as to be maintained at a ccnstant level, the concentration gradient will then extend out into the test fluid, and its slope will become non-linear and reduced as shown at broken line 66 in Figure 1~ d~e to the local depletion o~ oxygen in a layer shown between lines 62 and 68. With continued operation of the device and no replenishment of oxygen, the local depletion layer will continue to expand further out into the test fluid, distorting the concentration gradient more and more. The distortion of the concentration gradient reduces the ~:
3Q measu~ement sensitivity and change the mass flow rate of oxygen through the ~- .
,, ~
' ~3~
,. .
, . . . , , : . :
~'74~;7 membrane to the cathode, making measurement uncertain and even spurious over a period of time. In order to avoid such occurrence, seVeral means are customarily provided to minimize the extension of the depletion layer into the sample. A minimum fluid flow past the membrane-fluid interface is established, as for instance by stirring, and/or a relatively low permeability membrane may be used perhaps in combination with an inert spaeer positioned between the cathode and the membrane thereby increasing the thickness o~ the electrolyte layer, lessening the flux of the consumed species and minimizing the establishment of the depletion layer in the test fluid.
Further, i the fluid under measurement is a minute sample to which access is restricted, as is frequently the case with clinical samples of biological fluids or cells, depletion will continue until all of the oxygen is consumed. If the consumed oxygen is not or cannot be readily renewed, the measurements in a short time become inconclusive. The input ~low rate of the oxygen is often controlled by providing a relatively thick membrane which, however, acts to slow the response time of the device ~o changes in the oxygen concentration in the test fluid and lessens the magnitude of the signal current.
Further, it is common for the outer surface of the membrane, at 20 line 62, to become fouled to some extent while in use. This problem is particularly acute in applications where the sample is heavily laden with algae~ bacterial growth, or particulate. The additional impedance to oxygen . .
flux presented by the fouling causes a diminution of the sensor signal and renders the measurement inconclusive. Wipers to clean the interface, in com-bination with frequent replacement of the membranes, have been used to minimize this problem.
Some of the above mentioned disadvantages of the Clark type electrode cell are avoided by apparatus of the type described in United States patent : .
3,260,656 issued to James W. Ross, Jr. on July 12, 1966. The Ross apparatus utilizes a sandwich comprising a cathode and an anode with a spacer between.
~: ,., : -:
~: ,., : -:
-4-;
, ,, , . .. . . ~ . . - . .. ~ - .
~6J748~7 :' This sandwich is immersed in an electrolyte and is geometrically oriented so that the electrodes are ~arallel to a membrane which is permeable to the species being measured. The membrane combines with a housing to enclose the cathode-anode combination in an electrolyte. Typically, as for example, for the measurement of oxygen concentrationJ the Ross electrode cell utilizes an anode which is formed of a sheet-like element typically havi~g a thickness of about three mils and being porous to both the electrolyte and ~he electro-active species being measured. The anode is made of an electrically conduc-tive material, preferably a noble metal such as platinum, gold or the like.
To provide porosity the anode may be provided as a mesh or screen. The cathode, on the other hand, can be formed of substantially sheet-like material and may be solid and has a thickness which need be determined only by cost and structural strength considerations. The cathode is also preferably made of a noble metal and may be the same metal as the anode. The cathode-anode sandwich is disposed in an electrolyte which is preferably an aqueous solu-i tion of a base such as KOH. The spacer between the anode and cathode may, for example7 be a sheet-like porous element such as a woven fabric which is electrically non-conductive and chemically inert to the electrolyte.
With the Ross cell, if a potential is applied across the anode and .
~O cathode that is well below the decomposition voltage of the electrolyte andif there is no oxygen available in the electrolyte ~as from diffusion into the electrolyte through the membrane or from being dissolved in the latter), ~ ~;
only.a virtually constant7 minute, residual current will flow in the cathode- ~
.
anode circuit. If7 however, a supply of oxygen is presented to the outer surface of the membrane, as by contacting the membrane with a liquid having a-~i5s~1ff~d oxygen content, or by contacting it with a gas which includes oxygen, then because of ~he selective permeability of the membrane some oxygen will diffuse through the membrane and ~hence into the electrolyte to the cathode. I the potential at the cathode is more negative than the reduction ~
po~ential of oxygen-although below the decomposition potential of the electro- -~::
.
~)7~36~7 :
lyte, oxygen present at the cathode will be reduced. The reduction process is believed to be according to the same equation applicable to ~he cathodic reduction in the Clark apparatus. With the choice of electrode elements as mentioned above, the anode will cause, by ~irtue of the anode current, an oxidizing of the water in the electrolyte to generate oxygen according to the following H20 ~ 1/2 ~2 ~ 2~1* ~ 2e while at the cathode the oxygen reduction occurring is believed to be descri-bed by the same equation heretofore used to describe the cathode reduction in the Clark apparatus.
It will then be obvious that the system consumes the species being measured at one electrode such as the cathode and tends to generate a like quantity of that species at the opposite polarity electrode such as the anode, without changing the system such as changing the electrolyte pH and with an appropriate selection of electrode material consumption of the electrode can be avoided and the electrolyte will remain unchanged. The steady-state equality between generation and consumption of oxygen is, however, responsive to any change in concentration of the oxygen outside of the membrane. The gas tensions on both sides of the membrane will tend to reach an equilibrium 2a with one another, thus any change in ~as tension outside the membrane will upset the internal steady-state activity o~ the electrode system forcing it to a new steady-state by either increasing or decreasing the consumption of gas at one electrode with a corresponding increase or decrease in the genera-tion of gas at the other electrode. Each change in gas generation is thus in : ~
a direction tending to establish equilibrium between the gas tensions on oppo-site sides of the membrane and each change in the internal steady-state is accompanied by a change in current flow between the electrodes so that the current flow is generally maintained in direct proportion to the concentration of the oxygen gas, for example, outside the membrane.
Referring to Figure 2, there is shown graphically a concentration ~7~il67 diagram taken across the electrode-membrane structure of the Ross apparatus.
As in Figure 1, the ordinate 70 represents the relative fugacity of the particular electro~active species. The absicissa 72 represents distance from the cathode-electrolyte interface which is at the origin of the graph and hence, in a sense, the latter interface is line 70. Lines 74 and 76 then represent surfaces of an anode positioned between the cathode and membrane, with line 7~ representing the surface facing the cathode and line 76 the mem-brane. Line 78 is the outer surface of the membrane in contact with the test fluid. For the sake of clarity, no displacement between anocle and membrane is shown, hence line 76 can also be considered the anode-membrane interface. The displacement between the anode and cathode in the Ross apparatus is maintained by the spacer screen defining the electrolyte layer thickness between lines 70 and 7~.
; Given the geometry of the Ross apparatus, wherein the generating electrode lies between the consuming electrode and the test fluid, and assuming that the oxygen exhibits the same tension in both the electrolyte and test fluid and the concentration of oxygen in the test fluid is con-stant, the latter concentration is indicated by the horiæontal portion of the broken line 80 which extends from the test fluid into the membrane.
The concentration gradient, represented by the remainder of broken line 80, extends presumably from the anode-membrane interface to the cathode-electrolyte interface.
Whereas-the Ross cell effectively overcomes the problems of altera-tion of the electrodes and/or electrolyte, depletion of the oxygen from the test fluid, and extension of the depletion layer into the test fluid causing stirring and fouling dependence, certain other shortcomings are still evident.
Among them is the fact that readings with the Ross type cell, obtained by measuring the current flow between the electrodes, tend to stabilize within a maximum of one minute in accordance with the Ross patent. It has been 3Q foun~ that response times of this order for continuous measurements, such as ~74~367 the continuous measurement o oxygen concentration, are not suitable for many applications. Increasing the speed of response of the Ross type cell would require decreasing the combined thickness of the electrolyte layer ~i.e. the spacer screen thickness) and of the generating electrode, which are already at or near the practical minimum size for these components.
A further disadvantage is the fact that the diffusion layer thich-ness in the Ross cell is determined by the inter-electrode distance, which is subject to variation as the assembly is stressed by forces arising from temperature and/or pressure variations. Not only may the spacing vary, it cannot be less than a few mils to accommodate the spacer screen. Whereas the thickness of the diffusion layer is inversely related to the signal magnitude, an extremely thin and stabl0 diffusion layer is preferred.
A further disadvantage is the cumbersome nature of the layered structure, making reliable fabrication of Ross type devices difficult.
The ross approach is not the only attempt to overcome the recog-nized deficiencies of the Clark electrode. Among others, K.H. Mancy used a pulse polarographic technique and J.K. Fowler and K.B. Oldhen used semi-integral amperometry ~both reported in "Chemistry and Physics of Aqueous Gas Solutions The Electrochemical Society''1975) to minimize Clark electrode shortcomings. However, both did so at the expense of complex electronics and at the sacrifice o speed of responseJ which could exceed one minute.
It is therefore an object of this invention to provide an improved ; electrode structure which will have all of the advantages of the Clark cell and the improvements of the Ross cell ~hile overcoming their disadvantages.
Accordingly, the present invention contemplates an improved electrolytic~ce ; for measur m g species concentration in a fluid with increased sensitivity, ~ greater stability and shorter response time when compared to prior art devices - such as the Ross cell.
There is provided a voltammetric cell for measuring the concentration o electrochemically active species in a fluid which comprises an electrolytic .~
. . .
,~
.
.~ ., .
~079L~67 medium from which only the species is electrolytically generable. Barrier means such as a membrane may be provided where necessary for separating the electrolyte medium from the fluid whose concentration is to be measured.
That barrier means is permeable to the species. T:he cell also includes a plurality of spaced electrode surfaces arranged for connection to a power source so as to provide adjacent electrode surfaces with alternate polarit-ies. The surfaces are positioned so as to define a surface which is every-where equidistant from and in close spaced relationship to the barrier means with the electrolytic medium interposed therebetween and the electrode spacing and electrode sur~ace width determining apperiodicity of electrode position-ing sufficiently small with respect to the thickness and to the species permeability of both the barrier and the electrolyte so that as the species is generated at surfaces of one polarity the species is consumed at the surfaces of opposite polarity in quantity dependent upon the concentration of the species in the fluid being measured so that there is negligible flux of the species across the interface between the barrier and the fluid.
According to another aspect of the present invention~ there is . provided the method of measuring the concentration of an electrochemically ~:
- active species in a fluid comprising the steps of: immersing in said fluid : 20 an electrode assembly including: an electrolytic medium, barrier means selectively permeable to said species, first electrode means of material electrochemically inert to both said medium and said species and having sur-faces in contact with said medium, second electrode means o~ material electro-chemically inert to both said medium and said species, said second electrode means having surfaces in contact with said medium,} means for supporting said first and second electrode means to position their respective surfaces : in contact with said medium in an interleaved side by side relationship with said sur~aces equidistant from said barrier means and positioned so that the periodicity of the spacing of said electrode surfaces is sufficiently 3~ small ~ith respect to the thickness and species permeability of both said _ ~ _ .
-~7486'7 barrier means and said medium so that the species generated at the surfaces of said second electrode is consumed at the adjacent surfaces of said first electrode without any substantial transfer of said species across the interface between said barrier means and said fluid, and means connecting said first and second electrodes to a power source operable to bias said first and second electrodes at potentials to produce a current between said electrodes such that said species will be generated at said second electrode and consumed at said first 01ectrode in quantity dependent upon the tendency of said species to establish an equilibrium condition across said barrier means between the respective concentrations of said species in said medium and said fluid; and measuring said current flow as an indication of said species concentration in said fluid.
With reference to Figure 3 which shows an embodiment of the present invention, there is shown a portion of the electrolytic cell which consists of a non-conductive substrate 10 upon which there is deposited both anodic and cathodic electrode surfaces, preferably in the form of a thin metal film.
For3example, the cathode 14 is shown as having finger-like projections 14a projecting from the main body 14b. Those finger-like projections are interleaved with the finger-like projections 18a projecting from the main body 18b of the anode 18. The cathode and anode are interconnected in opera-tion by an electrical circuit through leads ?4 and 25 to an electricalcircuit connected to the respective terminals 29 and 30. That electrical circuit contains a series connected potential source 26 and an ammeter 28.
The structure of the electrolytic cell in one form is more com-pletely shown in cross-section in Figure 4 where the substrate 10 is show~
as having its cathode as formed by the finger-like projections 14a connected by way of line 24 to terminal 2~ and the projections 18a forming the anode connected by line 25 to terminal 30.- The main portions 14b and 18b of the cathode and anode may preferably be insulated from the circuit formed by the anode and cathode elements 14a and 18a by any of a number of means such as , .
. ' ' .
~7~7 by covering the respective main body portion with insulating material.
The anode and cathode surfaces are in contact with an electrolytic mcdium 32 which may advantageously consist of a thin film of liquid electro-lyte distributed over the electrode surfaces. That electrolyte may be con-tained at the electrode surfaces by the barrier means 34 which is a membrane permeable to the species whose concentration is to be measured by the cell.
If, for example, the cell shown in Figures 3 and 4 is to be used for the measurement of the concentration of oxygen in a fluid, the fluid is maintained in contact with the membrane 34 which can advantageously be con-structed of silicone rubber material, for example. The electrolyte 32 con-fined to contact with the surfaces of the electrode elements 14a and 18a may advantageously be KOH while the electrode material for the cathode 14a may be silver and the anode material for the anode 18a may be platinum.
; It will, of course, be understood that other noble metals may be used, however, the relative chemical inertness of the silver cathode and the platinum anode material has been found advantageous for the oxygen measure-ment. The substrate 10 may be of many suitable insulating materials such as glass, quartz, ceramics such as alumina, etc., having a thickness of greater than 10 mils, or sufficient to assure structural integrity.
The substrate 10 may advantageously be mounted on a supporting body over which the membrane 34 may be fitted and to which the membrane 34 may be affixed as by the use of cement or by being held in place by an "O" ring, for example. The method of mounting the substrate lO and the method of fixing and retaining the membrane 34 in place can~ of course, be selectively chosen depending upon the application for which the cell is to be used. It will, of course, be understood that the cell structure of Figures 3 and 4 may be suitable for the detection of species other than oxygen in which case appro-priate barrier 34 may be sel`e~cted so that it is permeable to the species being measured and the material from which the anode and cathode are made may be appropriately selected so that when used in conjunction with a selected . :
'~, .;:
~74867 : ~
electrolytic medium the particular species to be measured is generated at the surface of the electrode of one polarity while it is consumed at the surface of the electrode of the opposite polarity in a quantity which will be depen-dent on the concentration of the species in the fluid to be ~easured and so that there is a negligible transfer of the species across the interface be-tween the membrane barrier and the fluid as, for example, the surface 34a of the barrier 34. Operation of the cell in avoidance of any substantial trans-fer of species across interface 34a will depend upon the relative dimensions of the elements of the cell, that is, the spacing between the electrodes 14a and 18a and the thickness of the electrolytic medium in combination with the thickness of the barrier means. Those dimensions will be such that the flux of the species transferred between anode and cathode will be substan-tially all within the electrolytic medium and the barrier means.
As mentioned, the choice of electrolyte 32 will depend, of course, upon the species to be measured, it being necessary that the electrolytic medium formed by ~he electrolyte should be such that only the species to be measured is electrolytically generable therefrom.
The spacing of the electrode surfaces and the wid~h of those sur-faces in their side-by-side configuration, as shown in Figures 3 and 4, should, to fulfill the requirements of minimum transfer of species across interface 34a, be such that the periodicity of the electrode positioning es-tablished by the period P between corresponding portions of adjacent elec-trode surfaces of the same polarity is sufficiently small with respect to the thickness and species permeability of both the barrier 34 and the electrolytic medium 32 so that as the species generated at the electrode sur-face of one polarity is consumed at the surface of the opposite polarity with only an insignificantly small fraction transferring therebetween by crossing surface 34a. Thus the electrolyte is subjected to no net chemical reaction.
The reactions involved for the oxygen measuring cell may, for example, be 3Q the same as those set forth for the Ross cell.
, . .
~' ' ',.
, .. . .. - . ... - . , :
.: . : , . :, : , . . .
~07~86~7 It will, of course, be evident that the concentration of other electrochemically active species may be determined as~ for example, chlorine which can be determined using the oxidation reduction reaction 2e + Cl2 ~ 2Cl It will thus be evident that in an operation of the cell as, for example, in the measurement of the concentration of the oxygen in the sample being measured, the oxygen from the sample diffuses through the membrane 34 to bring the system to compositional equilibrium. Thus, the oxygen tension in the sample being measured will equilibrate with the average oxygen ten-sion in the electrolyte 32. All of the oxygen reaching the surface of the cathode is consumed while a like amount of oxygen is generated simultaneously at the anode. There then results an oxygen flux rom the anodes to the adjacent cathodes; however, since no net change in oxygen content results substantially no oxygen flux crosses the membrane interface 3~a unless the sample composition changes. This absence of flux crossing the membrane interface 34a occurs providing, as mentioned, that the periodicity of the electrode surface spacing P is sufficiently small with respect to the com-bined thickness of the barrier membrane 34 and electrolyte 32 and the species permeability of both the barrier and the electrolyte are such that substan-tially all of the oxygen flux is confined within the electrolyte and membrane.
It is not possible to show a graphical representation of the con-centration gradient across the selective membrane or through the electrolyte of the present invention as was done in Figures l and 2 for prior art devices.
This is the case because the concentration of oxygen, for example, varies not only with the distance from the electrode-electrolyte interface but also perio-dically across planes parallel to the plane of the electrode surfaces with the periodicity of the electrode structure. Figure 5 shows graphically the flux patterns occurring during operation of this invention as dotted lines 3~ superimposed on a cross-section view of the device. Oxygen is generated at - ,' .' ~
.~ . . . . , , -~4~'7 the anodes 18a which are on inert substrate 10, and diffuses to the cathodes 14a, some transversing the intermediate space via the electrolyte 32 and some through the permeable membrane 3~. With proper choice of membrane material and the membrane thickness/electrode period ratio, only an insigni-ficant quantity of oxygen will diffuse across interface 34a between the membrane and the test fluid.
With the geometrical configuration of the electrode surfaces, as shown in Figure 4, the spaced electrode surfaces are arranged for connection so that adjacent electrode surfaces have alternate polarities and so that those surfaces define a surface A-A which is everywhere equidistant from and in close space relationship to the barrier means comprising membrane 34 with the electrolyte medium 32 interposed therebetween.
With the above structure the deficiencies of the Clark cell as well as the Ross cell can be minimized or eliminated. This is the case since there is no net reaction in the cell with the exception of the consumption of a small amount of electrical power so that there is no reagent consumption or product build-up and no depletion of the oxygen in the sample.
Since there is substan~ially no oxygen flux through the outer sur-face of the membrane except during periods of transient change in the sample there will not bG a concentration gradient into the solution and therefore no minimum flow past the cell is required. The lack of oxygen 1ux through the outer surface of the membrane also removes the problem of the temperature coefficient for oxygen flux passing completely through the membrane no longer plays a roll in the cell's response other than in inluencing response time.
Thus, $he signal produced by the cell varies wi~h temperature as does the dif-~ .
fusion coefficient of the species being measured. With oxygen in aqueous solution variations would be two or three per cent per degree.
Other advantages to the present invention as compared with the Clark and ~oss cells include the fact that fouling of the membrane surface 3Q will not affect the calibration curve of the cell since there is no oxygen . .
. .
~1)74867 flux completely through the membrane during steady-state operation whereas, as pointed out, the Clark cell typically suffers from continual signal loss as fouling builds up. Thus, the calibration of the cell of the present invention remains unchanged. In addition~ the diffusion layer thickness is decreased by having the oxygen generated at an electrode surface in close prox1mity to the surface where it is depleted. For a given electrode area the oxygen concentration is higher for the sturcture of this invention than for the Clark or Ross cells. Therefore, an improvement in the sensi-tivity of the cell is inherent in the novel structure of the cell as des-cribed and an improvement in signal level of a factor in the order of 10 to100 has baen o~served in oxygen measurements where the periodicity of the spacing of the electrode surfaces is on the order of 1.6 mils with a membrane thickness of 5 mils.
The manner of construction, which may advantageously be utilized for the cell of Figures 3 and 4, can be any one of a number of techniques including thick and thin film techniques, however, it is believed that the thin film construction techniques which may, for example, involve the sput-tering and/or evaporation onto the substrate surface of a thin film of metal . . .
to form the electrode surfaces with the definition of the surface areas being accomplished by photo-etching processes is a preferred construction technique.
Th~ electrolyte solution itself may, as mentioned, be nothing more than a film of electrolyte over the electrode surfaces and the electrolyte solutions may be any of a number of alternatives including hydroxidesJ car-bonates, sulfates, or combinations thereof. With the structure set forth in Figures 3 and 4 the present invention provides a fast responding sensitive measurement in comparison with the prior art systems for in addition to over-coming the disadvantages of the Clark and Ross cells, as pointed out abo~e, the present invention provides a cell which not only has a faster response 3a time and an increased sensitivity but also a symmetrical response and an ', ~
. . :, . ' ' .: . ' ' ' ,, -.... . . . . . . .. . ..
6~7 avoidance of out-gassing at the anode which can occur, for example, with the Ross cell under certain conditions.
In Figure 6 there is shown a variation of the cell shown in Figures 3 and 4 in that the cell of Figure 6 includes, in addition t~ the cathode and anode surfaces 14a and 18a, respectively, a reference electrode 40 which is connected by way of line 42 to terminal 44.
The cell of Figure 6 may utilize a measu:ring circuit of the type shown in Figure 6 of the Ross patent for measuring species concentration.
While the anode and cathode surfaces~o`f the present invention have been shown in Figures 3, 4 and 6 in a form whereby the electrode surfaces define a flat plane A-A, the cell may be arranged so that the electrode surfaces define a cylindrical plane, for exampleJ as in the arrangement of ~igure 7 where the membrane ~6 is shown as being in a tubular form over-laying the cell electrodes and their support which consists of a central cylindrical body 48 of insulating material which has woun~ on its surface two interleaved wire electrodes forming spirals about the central support 48. These elec~rodes may consist of a wire 50 which forms an anode for the cell and the wire 52 which forms a cathode. In order to appropriately expose electrode surfaces to the electrolyte 54 which is interposed between the membrane 46 and the electrodes 50 and 52, the cell of Figure 7 may be constructed by winding upon the cylindrical base 48 the wires 50 and 52 and then immersing the resulting structure in a potting compound such as epoxy, for example, so that the assembly is completely potted. Then the potted assembly can be turned down on ~ lathe until sufficient amount of potting compounds is removed to expose - a small surface area of the wires 50 and 52 to form along the length of the ; cylindrical electrode assembly interleaved cathodic and~anodic surfaces.
The spacing between the wires 5~ and 52 and the width of the exposed ;~ ;
surfaces should be such that the appropriate periodicity of the electrode surface is provided and, as mentioned with regard to the structures of Figures 3 and 4~ that periodicity should be small with respect to the thickness and . '::
~74~67 the species permeability of both the barrier and the electrolyte so that as the species is generated at the surface of one electrode it is consumed at the surface of the other electrode in a quantity dependent on the concentra-tion of the species in the sample fluid being measured with negligible trans-fer of the species across interface between the barrier membrane ~6 and the sample being measured.
The cylindrical electrode inserted in the membrane 46, as shown in Figure 7, is supported by a non-conducting body portion 56 to which the membrane 46 is closely fitted so as to retain the electrolyte 54 within the spacing between the membrane 46 and the inserted electrode structure carrying the electrode surfaces on wires 50 and 52. As with the structure of the other configurations the electrolyte need consist only of a thin film of electrolyte solution in order to maximize the sensitivity and minimize the response time of the electrode.
The electrolyte 32 of Figures 4, 5 and 6 as well as the electrolyte 54 of Figure 7 can be a solid polymer electrolyte instead of being a liquid electrolyte as mentioned. The polymer electrolyte must allow diffusion of all reactants and products between the cathodes and anodes as well as allowing exchange of the measured gas with the test fluid. It must also have satis-factory chemical, thermal and dimensional stability. Such polymer electro-lytes may be poly-sulfonic acids typically polystyrene sulfonic acid or per-fluoro linear polymers (such as marketed under the name "Nafion" by Du Pont).
The barrier 34 of Figures ~, 5 and 6 and the barrier 46 of Figure 7 may be omitted when there is no necessity to isolate the test fluid from the electrolyte. For example, when the test fluid is a gas, such isolation is not necessary. This is particularly true when the electrolyte is a solid The following example is illustrative of the construction and operation of a device shown in Figure 7. A non-conducting body 1.587 cm in diameter was formed of polyformaldehyde such as Delrin marketed by Du Pont.
3~ Silver wire .006" in diameter was used for the cathode and .006" diameter '.
.'.
. .
.:
~7~;7 -:
platinum wire for the anode. Forty turns of the wires were wound in a bifilar configuration around the cylinder, the wires spaced .OQ6" apart.
The assembly was then potted in an epoxy and, after curing, the epoxy sur-face was removed to expose the wire surfaces. A thin layer of O.IM NaOH was held against the electrode surfaces by a .005" thick silicone rubber membrane.
The assembly was immersed in an aqueous solution which was alternately purged with air or nit~ogen. During nitrogen purge a signal of .08 ma was obtained, whereas in air purged solution the signal was 1.73 ma. The response time was 5 seconds for 90% response and approximately 8 seconds for the full change in outpuk.
The following example is illustrative of the construction and opera-tion of a device shown in Figures 3 and 4. A non-conductive glass substrate .5" square and .02" thick was used, onto which was sputtered 200 platinum electrode surfaces 10 micron wide and 4 mm long separated by 10 micron spacers.
ConnectioniWaS made such that there were 100 cathodes alternating with 100 anodes. Bus bars and lead wires were isolated from contact with the electro-lyte by an epoxy film coating. An extract of a solid cation electrolyte such as that previously identified as Nafion was deposited as a thin film on the electrode pattern and covered wlth a thin layer of silicone rubber. When immersed in an N2 purges acqueOu5solution, the output current was 0.1 micro-amperes. In air saturated solution, vigorously stirred, the signal was 12.4 microamperes, which decayed to 11.8 microamperes when the solution was left with no stirring for overone hour. A Clark type device operated in like manner lost over 70% of its signal when left unstirred.
It will be apparent to those skilled in the art that many modifica-tions of the invention as thus described can be made. For example, a large number of electrolytes may be used. Indeed~ under some circumstances the electrolyte may be a molten salt, and the enclosure means a membrane selected accordingly to have appropriate temperature resistant characteriskics. Ik 3~ ~ill also be apparent that where the species to be measured is reducible, the ~L~7~
generating electrode is an anode and the consuming electrode is a cathode.
However~ if the species to be measured is oxidizable9 the generating elec-trode will be a negative electrode and the consuming electrode will be an anode or positive electrode.
'.
,' '',
, ,, , . .. . . ~ . . - . .. ~ - .
~6J748~7 :' This sandwich is immersed in an electrolyte and is geometrically oriented so that the electrodes are ~arallel to a membrane which is permeable to the species being measured. The membrane combines with a housing to enclose the cathode-anode combination in an electrolyte. Typically, as for example, for the measurement of oxygen concentrationJ the Ross electrode cell utilizes an anode which is formed of a sheet-like element typically havi~g a thickness of about three mils and being porous to both the electrolyte and ~he electro-active species being measured. The anode is made of an electrically conduc-tive material, preferably a noble metal such as platinum, gold or the like.
To provide porosity the anode may be provided as a mesh or screen. The cathode, on the other hand, can be formed of substantially sheet-like material and may be solid and has a thickness which need be determined only by cost and structural strength considerations. The cathode is also preferably made of a noble metal and may be the same metal as the anode. The cathode-anode sandwich is disposed in an electrolyte which is preferably an aqueous solu-i tion of a base such as KOH. The spacer between the anode and cathode may, for example7 be a sheet-like porous element such as a woven fabric which is electrically non-conductive and chemically inert to the electrolyte.
With the Ross cell, if a potential is applied across the anode and .
~O cathode that is well below the decomposition voltage of the electrolyte andif there is no oxygen available in the electrolyte ~as from diffusion into the electrolyte through the membrane or from being dissolved in the latter), ~ ~;
only.a virtually constant7 minute, residual current will flow in the cathode- ~
.
anode circuit. If7 however, a supply of oxygen is presented to the outer surface of the membrane, as by contacting the membrane with a liquid having a-~i5s~1ff~d oxygen content, or by contacting it with a gas which includes oxygen, then because of ~he selective permeability of the membrane some oxygen will diffuse through the membrane and ~hence into the electrolyte to the cathode. I the potential at the cathode is more negative than the reduction ~
po~ential of oxygen-although below the decomposition potential of the electro- -~::
.
~)7~36~7 :
lyte, oxygen present at the cathode will be reduced. The reduction process is believed to be according to the same equation applicable to ~he cathodic reduction in the Clark apparatus. With the choice of electrode elements as mentioned above, the anode will cause, by ~irtue of the anode current, an oxidizing of the water in the electrolyte to generate oxygen according to the following H20 ~ 1/2 ~2 ~ 2~1* ~ 2e while at the cathode the oxygen reduction occurring is believed to be descri-bed by the same equation heretofore used to describe the cathode reduction in the Clark apparatus.
It will then be obvious that the system consumes the species being measured at one electrode such as the cathode and tends to generate a like quantity of that species at the opposite polarity electrode such as the anode, without changing the system such as changing the electrolyte pH and with an appropriate selection of electrode material consumption of the electrode can be avoided and the electrolyte will remain unchanged. The steady-state equality between generation and consumption of oxygen is, however, responsive to any change in concentration of the oxygen outside of the membrane. The gas tensions on both sides of the membrane will tend to reach an equilibrium 2a with one another, thus any change in ~as tension outside the membrane will upset the internal steady-state activity o~ the electrode system forcing it to a new steady-state by either increasing or decreasing the consumption of gas at one electrode with a corresponding increase or decrease in the genera-tion of gas at the other electrode. Each change in gas generation is thus in : ~
a direction tending to establish equilibrium between the gas tensions on oppo-site sides of the membrane and each change in the internal steady-state is accompanied by a change in current flow between the electrodes so that the current flow is generally maintained in direct proportion to the concentration of the oxygen gas, for example, outside the membrane.
Referring to Figure 2, there is shown graphically a concentration ~7~il67 diagram taken across the electrode-membrane structure of the Ross apparatus.
As in Figure 1, the ordinate 70 represents the relative fugacity of the particular electro~active species. The absicissa 72 represents distance from the cathode-electrolyte interface which is at the origin of the graph and hence, in a sense, the latter interface is line 70. Lines 74 and 76 then represent surfaces of an anode positioned between the cathode and membrane, with line 7~ representing the surface facing the cathode and line 76 the mem-brane. Line 78 is the outer surface of the membrane in contact with the test fluid. For the sake of clarity, no displacement between anocle and membrane is shown, hence line 76 can also be considered the anode-membrane interface. The displacement between the anode and cathode in the Ross apparatus is maintained by the spacer screen defining the electrolyte layer thickness between lines 70 and 7~.
; Given the geometry of the Ross apparatus, wherein the generating electrode lies between the consuming electrode and the test fluid, and assuming that the oxygen exhibits the same tension in both the electrolyte and test fluid and the concentration of oxygen in the test fluid is con-stant, the latter concentration is indicated by the horiæontal portion of the broken line 80 which extends from the test fluid into the membrane.
The concentration gradient, represented by the remainder of broken line 80, extends presumably from the anode-membrane interface to the cathode-electrolyte interface.
Whereas-the Ross cell effectively overcomes the problems of altera-tion of the electrodes and/or electrolyte, depletion of the oxygen from the test fluid, and extension of the depletion layer into the test fluid causing stirring and fouling dependence, certain other shortcomings are still evident.
Among them is the fact that readings with the Ross type cell, obtained by measuring the current flow between the electrodes, tend to stabilize within a maximum of one minute in accordance with the Ross patent. It has been 3Q foun~ that response times of this order for continuous measurements, such as ~74~367 the continuous measurement o oxygen concentration, are not suitable for many applications. Increasing the speed of response of the Ross type cell would require decreasing the combined thickness of the electrolyte layer ~i.e. the spacer screen thickness) and of the generating electrode, which are already at or near the practical minimum size for these components.
A further disadvantage is the fact that the diffusion layer thich-ness in the Ross cell is determined by the inter-electrode distance, which is subject to variation as the assembly is stressed by forces arising from temperature and/or pressure variations. Not only may the spacing vary, it cannot be less than a few mils to accommodate the spacer screen. Whereas the thickness of the diffusion layer is inversely related to the signal magnitude, an extremely thin and stabl0 diffusion layer is preferred.
A further disadvantage is the cumbersome nature of the layered structure, making reliable fabrication of Ross type devices difficult.
The ross approach is not the only attempt to overcome the recog-nized deficiencies of the Clark electrode. Among others, K.H. Mancy used a pulse polarographic technique and J.K. Fowler and K.B. Oldhen used semi-integral amperometry ~both reported in "Chemistry and Physics of Aqueous Gas Solutions The Electrochemical Society''1975) to minimize Clark electrode shortcomings. However, both did so at the expense of complex electronics and at the sacrifice o speed of responseJ which could exceed one minute.
It is therefore an object of this invention to provide an improved ; electrode structure which will have all of the advantages of the Clark cell and the improvements of the Ross cell ~hile overcoming their disadvantages.
Accordingly, the present invention contemplates an improved electrolytic~ce ; for measur m g species concentration in a fluid with increased sensitivity, ~ greater stability and shorter response time when compared to prior art devices - such as the Ross cell.
There is provided a voltammetric cell for measuring the concentration o electrochemically active species in a fluid which comprises an electrolytic .~
. . .
,~
.
.~ ., .
~079L~67 medium from which only the species is electrolytically generable. Barrier means such as a membrane may be provided where necessary for separating the electrolyte medium from the fluid whose concentration is to be measured.
That barrier means is permeable to the species. T:he cell also includes a plurality of spaced electrode surfaces arranged for connection to a power source so as to provide adjacent electrode surfaces with alternate polarit-ies. The surfaces are positioned so as to define a surface which is every-where equidistant from and in close spaced relationship to the barrier means with the electrolytic medium interposed therebetween and the electrode spacing and electrode sur~ace width determining apperiodicity of electrode position-ing sufficiently small with respect to the thickness and to the species permeability of both the barrier and the electrolyte so that as the species is generated at surfaces of one polarity the species is consumed at the surfaces of opposite polarity in quantity dependent upon the concentration of the species in the fluid being measured so that there is negligible flux of the species across the interface between the barrier and the fluid.
According to another aspect of the present invention~ there is . provided the method of measuring the concentration of an electrochemically ~:
- active species in a fluid comprising the steps of: immersing in said fluid : 20 an electrode assembly including: an electrolytic medium, barrier means selectively permeable to said species, first electrode means of material electrochemically inert to both said medium and said species and having sur-faces in contact with said medium, second electrode means o~ material electro-chemically inert to both said medium and said species, said second electrode means having surfaces in contact with said medium,} means for supporting said first and second electrode means to position their respective surfaces : in contact with said medium in an interleaved side by side relationship with said sur~aces equidistant from said barrier means and positioned so that the periodicity of the spacing of said electrode surfaces is sufficiently 3~ small ~ith respect to the thickness and species permeability of both said _ ~ _ .
-~7486'7 barrier means and said medium so that the species generated at the surfaces of said second electrode is consumed at the adjacent surfaces of said first electrode without any substantial transfer of said species across the interface between said barrier means and said fluid, and means connecting said first and second electrodes to a power source operable to bias said first and second electrodes at potentials to produce a current between said electrodes such that said species will be generated at said second electrode and consumed at said first 01ectrode in quantity dependent upon the tendency of said species to establish an equilibrium condition across said barrier means between the respective concentrations of said species in said medium and said fluid; and measuring said current flow as an indication of said species concentration in said fluid.
With reference to Figure 3 which shows an embodiment of the present invention, there is shown a portion of the electrolytic cell which consists of a non-conductive substrate 10 upon which there is deposited both anodic and cathodic electrode surfaces, preferably in the form of a thin metal film.
For3example, the cathode 14 is shown as having finger-like projections 14a projecting from the main body 14b. Those finger-like projections are interleaved with the finger-like projections 18a projecting from the main body 18b of the anode 18. The cathode and anode are interconnected in opera-tion by an electrical circuit through leads ?4 and 25 to an electricalcircuit connected to the respective terminals 29 and 30. That electrical circuit contains a series connected potential source 26 and an ammeter 28.
The structure of the electrolytic cell in one form is more com-pletely shown in cross-section in Figure 4 where the substrate 10 is show~
as having its cathode as formed by the finger-like projections 14a connected by way of line 24 to terminal 2~ and the projections 18a forming the anode connected by line 25 to terminal 30.- The main portions 14b and 18b of the cathode and anode may preferably be insulated from the circuit formed by the anode and cathode elements 14a and 18a by any of a number of means such as , .
. ' ' .
~7~7 by covering the respective main body portion with insulating material.
The anode and cathode surfaces are in contact with an electrolytic mcdium 32 which may advantageously consist of a thin film of liquid electro-lyte distributed over the electrode surfaces. That electrolyte may be con-tained at the electrode surfaces by the barrier means 34 which is a membrane permeable to the species whose concentration is to be measured by the cell.
If, for example, the cell shown in Figures 3 and 4 is to be used for the measurement of the concentration of oxygen in a fluid, the fluid is maintained in contact with the membrane 34 which can advantageously be con-structed of silicone rubber material, for example. The electrolyte 32 con-fined to contact with the surfaces of the electrode elements 14a and 18a may advantageously be KOH while the electrode material for the cathode 14a may be silver and the anode material for the anode 18a may be platinum.
; It will, of course, be understood that other noble metals may be used, however, the relative chemical inertness of the silver cathode and the platinum anode material has been found advantageous for the oxygen measure-ment. The substrate 10 may be of many suitable insulating materials such as glass, quartz, ceramics such as alumina, etc., having a thickness of greater than 10 mils, or sufficient to assure structural integrity.
The substrate 10 may advantageously be mounted on a supporting body over which the membrane 34 may be fitted and to which the membrane 34 may be affixed as by the use of cement or by being held in place by an "O" ring, for example. The method of mounting the substrate lO and the method of fixing and retaining the membrane 34 in place can~ of course, be selectively chosen depending upon the application for which the cell is to be used. It will, of course, be understood that the cell structure of Figures 3 and 4 may be suitable for the detection of species other than oxygen in which case appro-priate barrier 34 may be sel`e~cted so that it is permeable to the species being measured and the material from which the anode and cathode are made may be appropriately selected so that when used in conjunction with a selected . :
'~, .;:
~74867 : ~
electrolytic medium the particular species to be measured is generated at the surface of the electrode of one polarity while it is consumed at the surface of the electrode of the opposite polarity in a quantity which will be depen-dent on the concentration of the species in the fluid to be ~easured and so that there is a negligible transfer of the species across the interface be-tween the membrane barrier and the fluid as, for example, the surface 34a of the barrier 34. Operation of the cell in avoidance of any substantial trans-fer of species across interface 34a will depend upon the relative dimensions of the elements of the cell, that is, the spacing between the electrodes 14a and 18a and the thickness of the electrolytic medium in combination with the thickness of the barrier means. Those dimensions will be such that the flux of the species transferred between anode and cathode will be substan-tially all within the electrolytic medium and the barrier means.
As mentioned, the choice of electrolyte 32 will depend, of course, upon the species to be measured, it being necessary that the electrolytic medium formed by ~he electrolyte should be such that only the species to be measured is electrolytically generable therefrom.
The spacing of the electrode surfaces and the wid~h of those sur-faces in their side-by-side configuration, as shown in Figures 3 and 4, should, to fulfill the requirements of minimum transfer of species across interface 34a, be such that the periodicity of the electrode positioning es-tablished by the period P between corresponding portions of adjacent elec-trode surfaces of the same polarity is sufficiently small with respect to the thickness and species permeability of both the barrier 34 and the electrolytic medium 32 so that as the species generated at the electrode sur-face of one polarity is consumed at the surface of the opposite polarity with only an insignificantly small fraction transferring therebetween by crossing surface 34a. Thus the electrolyte is subjected to no net chemical reaction.
The reactions involved for the oxygen measuring cell may, for example, be 3Q the same as those set forth for the Ross cell.
, . .
~' ' ',.
, .. . .. - . ... - . , :
.: . : , . :, : , . . .
~07~86~7 It will, of course, be evident that the concentration of other electrochemically active species may be determined as~ for example, chlorine which can be determined using the oxidation reduction reaction 2e + Cl2 ~ 2Cl It will thus be evident that in an operation of the cell as, for example, in the measurement of the concentration of the oxygen in the sample being measured, the oxygen from the sample diffuses through the membrane 34 to bring the system to compositional equilibrium. Thus, the oxygen tension in the sample being measured will equilibrate with the average oxygen ten-sion in the electrolyte 32. All of the oxygen reaching the surface of the cathode is consumed while a like amount of oxygen is generated simultaneously at the anode. There then results an oxygen flux rom the anodes to the adjacent cathodes; however, since no net change in oxygen content results substantially no oxygen flux crosses the membrane interface 3~a unless the sample composition changes. This absence of flux crossing the membrane interface 34a occurs providing, as mentioned, that the periodicity of the electrode surface spacing P is sufficiently small with respect to the com-bined thickness of the barrier membrane 34 and electrolyte 32 and the species permeability of both the barrier and the electrolyte are such that substan-tially all of the oxygen flux is confined within the electrolyte and membrane.
It is not possible to show a graphical representation of the con-centration gradient across the selective membrane or through the electrolyte of the present invention as was done in Figures l and 2 for prior art devices.
This is the case because the concentration of oxygen, for example, varies not only with the distance from the electrode-electrolyte interface but also perio-dically across planes parallel to the plane of the electrode surfaces with the periodicity of the electrode structure. Figure 5 shows graphically the flux patterns occurring during operation of this invention as dotted lines 3~ superimposed on a cross-section view of the device. Oxygen is generated at - ,' .' ~
.~ . . . . , , -~4~'7 the anodes 18a which are on inert substrate 10, and diffuses to the cathodes 14a, some transversing the intermediate space via the electrolyte 32 and some through the permeable membrane 3~. With proper choice of membrane material and the membrane thickness/electrode period ratio, only an insigni-ficant quantity of oxygen will diffuse across interface 34a between the membrane and the test fluid.
With the geometrical configuration of the electrode surfaces, as shown in Figure 4, the spaced electrode surfaces are arranged for connection so that adjacent electrode surfaces have alternate polarities and so that those surfaces define a surface A-A which is everywhere equidistant from and in close space relationship to the barrier means comprising membrane 34 with the electrolyte medium 32 interposed therebetween.
With the above structure the deficiencies of the Clark cell as well as the Ross cell can be minimized or eliminated. This is the case since there is no net reaction in the cell with the exception of the consumption of a small amount of electrical power so that there is no reagent consumption or product build-up and no depletion of the oxygen in the sample.
Since there is substan~ially no oxygen flux through the outer sur-face of the membrane except during periods of transient change in the sample there will not bG a concentration gradient into the solution and therefore no minimum flow past the cell is required. The lack of oxygen 1ux through the outer surface of the membrane also removes the problem of the temperature coefficient for oxygen flux passing completely through the membrane no longer plays a roll in the cell's response other than in inluencing response time.
Thus, $he signal produced by the cell varies wi~h temperature as does the dif-~ .
fusion coefficient of the species being measured. With oxygen in aqueous solution variations would be two or three per cent per degree.
Other advantages to the present invention as compared with the Clark and ~oss cells include the fact that fouling of the membrane surface 3Q will not affect the calibration curve of the cell since there is no oxygen . .
. .
~1)74867 flux completely through the membrane during steady-state operation whereas, as pointed out, the Clark cell typically suffers from continual signal loss as fouling builds up. Thus, the calibration of the cell of the present invention remains unchanged. In addition~ the diffusion layer thickness is decreased by having the oxygen generated at an electrode surface in close prox1mity to the surface where it is depleted. For a given electrode area the oxygen concentration is higher for the sturcture of this invention than for the Clark or Ross cells. Therefore, an improvement in the sensi-tivity of the cell is inherent in the novel structure of the cell as des-cribed and an improvement in signal level of a factor in the order of 10 to100 has baen o~served in oxygen measurements where the periodicity of the spacing of the electrode surfaces is on the order of 1.6 mils with a membrane thickness of 5 mils.
The manner of construction, which may advantageously be utilized for the cell of Figures 3 and 4, can be any one of a number of techniques including thick and thin film techniques, however, it is believed that the thin film construction techniques which may, for example, involve the sput-tering and/or evaporation onto the substrate surface of a thin film of metal . . .
to form the electrode surfaces with the definition of the surface areas being accomplished by photo-etching processes is a preferred construction technique.
Th~ electrolyte solution itself may, as mentioned, be nothing more than a film of electrolyte over the electrode surfaces and the electrolyte solutions may be any of a number of alternatives including hydroxidesJ car-bonates, sulfates, or combinations thereof. With the structure set forth in Figures 3 and 4 the present invention provides a fast responding sensitive measurement in comparison with the prior art systems for in addition to over-coming the disadvantages of the Clark and Ross cells, as pointed out abo~e, the present invention provides a cell which not only has a faster response 3a time and an increased sensitivity but also a symmetrical response and an ', ~
. . :, . ' ' .: . ' ' ' ,, -.... . . . . . . .. . ..
6~7 avoidance of out-gassing at the anode which can occur, for example, with the Ross cell under certain conditions.
In Figure 6 there is shown a variation of the cell shown in Figures 3 and 4 in that the cell of Figure 6 includes, in addition t~ the cathode and anode surfaces 14a and 18a, respectively, a reference electrode 40 which is connected by way of line 42 to terminal 44.
The cell of Figure 6 may utilize a measu:ring circuit of the type shown in Figure 6 of the Ross patent for measuring species concentration.
While the anode and cathode surfaces~o`f the present invention have been shown in Figures 3, 4 and 6 in a form whereby the electrode surfaces define a flat plane A-A, the cell may be arranged so that the electrode surfaces define a cylindrical plane, for exampleJ as in the arrangement of ~igure 7 where the membrane ~6 is shown as being in a tubular form over-laying the cell electrodes and their support which consists of a central cylindrical body 48 of insulating material which has woun~ on its surface two interleaved wire electrodes forming spirals about the central support 48. These elec~rodes may consist of a wire 50 which forms an anode for the cell and the wire 52 which forms a cathode. In order to appropriately expose electrode surfaces to the electrolyte 54 which is interposed between the membrane 46 and the electrodes 50 and 52, the cell of Figure 7 may be constructed by winding upon the cylindrical base 48 the wires 50 and 52 and then immersing the resulting structure in a potting compound such as epoxy, for example, so that the assembly is completely potted. Then the potted assembly can be turned down on ~ lathe until sufficient amount of potting compounds is removed to expose - a small surface area of the wires 50 and 52 to form along the length of the ; cylindrical electrode assembly interleaved cathodic and~anodic surfaces.
The spacing between the wires 5~ and 52 and the width of the exposed ;~ ;
surfaces should be such that the appropriate periodicity of the electrode surface is provided and, as mentioned with regard to the structures of Figures 3 and 4~ that periodicity should be small with respect to the thickness and . '::
~74~67 the species permeability of both the barrier and the electrolyte so that as the species is generated at the surface of one electrode it is consumed at the surface of the other electrode in a quantity dependent on the concentra-tion of the species in the sample fluid being measured with negligible trans-fer of the species across interface between the barrier membrane ~6 and the sample being measured.
The cylindrical electrode inserted in the membrane 46, as shown in Figure 7, is supported by a non-conducting body portion 56 to which the membrane 46 is closely fitted so as to retain the electrolyte 54 within the spacing between the membrane 46 and the inserted electrode structure carrying the electrode surfaces on wires 50 and 52. As with the structure of the other configurations the electrolyte need consist only of a thin film of electrolyte solution in order to maximize the sensitivity and minimize the response time of the electrode.
The electrolyte 32 of Figures 4, 5 and 6 as well as the electrolyte 54 of Figure 7 can be a solid polymer electrolyte instead of being a liquid electrolyte as mentioned. The polymer electrolyte must allow diffusion of all reactants and products between the cathodes and anodes as well as allowing exchange of the measured gas with the test fluid. It must also have satis-factory chemical, thermal and dimensional stability. Such polymer electro-lytes may be poly-sulfonic acids typically polystyrene sulfonic acid or per-fluoro linear polymers (such as marketed under the name "Nafion" by Du Pont).
The barrier 34 of Figures ~, 5 and 6 and the barrier 46 of Figure 7 may be omitted when there is no necessity to isolate the test fluid from the electrolyte. For example, when the test fluid is a gas, such isolation is not necessary. This is particularly true when the electrolyte is a solid The following example is illustrative of the construction and operation of a device shown in Figure 7. A non-conducting body 1.587 cm in diameter was formed of polyformaldehyde such as Delrin marketed by Du Pont.
3~ Silver wire .006" in diameter was used for the cathode and .006" diameter '.
.'.
. .
.:
~7~;7 -:
platinum wire for the anode. Forty turns of the wires were wound in a bifilar configuration around the cylinder, the wires spaced .OQ6" apart.
The assembly was then potted in an epoxy and, after curing, the epoxy sur-face was removed to expose the wire surfaces. A thin layer of O.IM NaOH was held against the electrode surfaces by a .005" thick silicone rubber membrane.
The assembly was immersed in an aqueous solution which was alternately purged with air or nit~ogen. During nitrogen purge a signal of .08 ma was obtained, whereas in air purged solution the signal was 1.73 ma. The response time was 5 seconds for 90% response and approximately 8 seconds for the full change in outpuk.
The following example is illustrative of the construction and opera-tion of a device shown in Figures 3 and 4. A non-conductive glass substrate .5" square and .02" thick was used, onto which was sputtered 200 platinum electrode surfaces 10 micron wide and 4 mm long separated by 10 micron spacers.
ConnectioniWaS made such that there were 100 cathodes alternating with 100 anodes. Bus bars and lead wires were isolated from contact with the electro-lyte by an epoxy film coating. An extract of a solid cation electrolyte such as that previously identified as Nafion was deposited as a thin film on the electrode pattern and covered wlth a thin layer of silicone rubber. When immersed in an N2 purges acqueOu5solution, the output current was 0.1 micro-amperes. In air saturated solution, vigorously stirred, the signal was 12.4 microamperes, which decayed to 11.8 microamperes when the solution was left with no stirring for overone hour. A Clark type device operated in like manner lost over 70% of its signal when left unstirred.
It will be apparent to those skilled in the art that many modifica-tions of the invention as thus described can be made. For example, a large number of electrolytes may be used. Indeed~ under some circumstances the electrolyte may be a molten salt, and the enclosure means a membrane selected accordingly to have appropriate temperature resistant characteriskics. Ik 3~ ~ill also be apparent that where the species to be measured is reducible, the ~L~7~
generating electrode is an anode and the consuming electrode is a cathode.
However~ if the species to be measured is oxidizable9 the generating elec-trode will be a negative electrode and the consuming electrode will be an anode or positive electrode.
'.
,' '',
Claims (32)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A voltammetric cell for measuring the concentration of electroch-emically active species in a fluid, comprising in combination: an electro-lytic medium from which only said species is electrolytically generable; and a plurality of spaced electrode surfaces arranged for connection to a power source so that adjacent electrode surfaces have alternate polarities, said surfaces being positioned to define a surface overlaid with a uniform thick-ness of the electrolytic medium and the spacing and width of said electrode surfaces determining a periodicity of electrode surface positioning suffici-ently small with respect to the combined effect of the thickness and species permeability of said electrolytic medium so that as said species is genera-ted at electrode surfaces of one polarity it is consumed at the electrode surfaces of opposite polarity in quantity dependent on the concentration of the species in said fluid with a negligible transfer of the species across the interface with said fluid.
2. A voltammetric cell as set forth in claim 1 in which said fluid is a gas.
3. A voltammetric cell as set forth in claim 1 in which the surface defined by said electrode surfaces is a flat plane.
4. A voltammetric cell as set forth in claim 1 in which the surface defined by said electrode surfaces is a cylindrical surface.
5. A voltammetric cell as set forth in claim 1 in which said spaced electrode surfaces are formed by a plurality of interleaved narrow strips of thin metal film deposited on an insulating flat substrate so as to be closely spaced.
6. A voltammetric cell as set forth in claim 1 in which said electro-lytic medium is a thin film of liquid electrolyte.
.ANG.
.ANG.
7. A voltammetric cell as set forth in claim 1 in which said electro-lytic medium is a thin film of solid electrolyte.
8. A voltammetric cell as set forth in claim 1 which includes a ref-erence electrode contacting said medium and spaced from the other electrodes.
9. A voltammetric cell as set forth in claim 1 in which said species is oxygen, said electrolytic medium is a solid polymer electrolyte; and said electrode surfaces are formed by interleaved narrow strips of thin metal film deposited on a flat insulating substrate.
10. A voltammetric cell for measuring the concentration of electrochem-ically active species in a fluid, comprising in combination: an electrolytic medium from which only said species is electrolytically generable; barrier means for separating said electrolytic medium from said fluid, said barrier means being permeable to said species; and a plurality of spaced electrode surfaces arranged for connection to a power source so that adjacent electrode surfaces have alternate polarities, said surfaces being positioned to define a surface that is everywhere equidistant from and in close spaced relation-ship to said barrier means with the electrolytic medium interposed therebet-ween, and the spacing and width of said electrode surfaces determining a periodicity of electrode surface positioning sufficiently small with respect to the combined effect of the thickness and species permeability of both said barrier and said electrolytic medium so that as said species is generated at electrode surfaces of one polarity it is consumed at the electrode surfaces of opposite polarity in quantity dependent on the concentration of the speci-es in said fluid with negligible transfer of the species across the interface between said barrier and said fluid.
11. A voltammetric cell as set forth in claim 10 in which said barrier means is a thin membrane.
12. A voltammetric cell as set forth in claim 10 in which said species is oxygen, said electrolytic medium is a solid polymer electrolyte, said barrier means is a thin membrane of silicone rubber, and said electrode sur-faces are formed by interleaved narrow strips of thin metal film deposited on a flat insulating substrate.
13. A voltammetric cell as set forth in claim 10 in which said electrode surfaces are formed by two wires spirally wound on a cylindrical base in an interleaving relationship with said windings being potted and machined so that surfaces of both of said wires form electrode surfaces defining a sur-face which is cylindrical.
14. A voltammetric cell for measuring the concentration of electro-chemically active species in a fluid, comprising in combination: an electro-lytic medium from which only said species is electrolytically generable;
barrier means for separating said electrolytic medium from said fluid, said barrier means being permeable to said species; a plurality of anodic elec-trode surfaces spaced so as to define a surface; a plurality of cathodic electrode surfaces spaced in said surface defined by said anodic surfaces and interleaved therewith; and an insulating substrate carrying said sur-faces spaced so that the periodicity of electrode surface spacing is suffi-ciently small with respect to the thickness of both said barrier and said electrolyte so that in operation of said cell a negligible quantity of said species is transferred between said electrode surfaces over a path crossing the interface between said barrier and said fluid.
barrier means for separating said electrolytic medium from said fluid, said barrier means being permeable to said species; a plurality of anodic elec-trode surfaces spaced so as to define a surface; a plurality of cathodic electrode surfaces spaced in said surface defined by said anodic surfaces and interleaved therewith; and an insulating substrate carrying said sur-faces spaced so that the periodicity of electrode surface spacing is suffi-ciently small with respect to the thickness of both said barrier and said electrolyte so that in operation of said cell a negligible quantity of said species is transferred between said electrode surfaces over a path crossing the interface between said barrier and said fluid.
15. A voltammetric cell as set forth in claim 14, in which: said electrolytic medium is a thin film of electrolyte; said barrier means is a thin membrane; and said anodic and cathodic electrode surfaces are formed by thin films of metal inert to said species.
16. A voltammetric cell as set forth in claim 15, in which: said electrolytic medium is a solid electrolyte; said barrier means is a thin membrane of silicone rubber; said anodic electrode surfaces are of platinum;
and said cathodic electrode surfaces are of silver.
and said cathodic electrode surfaces are of silver.
17. A voltammetric cell as set forth in claim 16 in which said solid electrolyte is a polymer.
18. In an electrode assembly for measuring the concentration of a speci-fic electrochemically active species in a fluid of the type which includes in combination: an electrolytic medium; first electrode means having surfaces in contact with said medium; barrier means for separating said medium from said fluid, and being selectively permeable to said species, and in contact with said medium; an electrical power source connected for biasing said first electrode means at a potential at which said species in said medium will be consumed at said surfaces of said first electrode means; and second electrode means having surfaces in contact with said medium and con-nected to said power source for completing a circuit in which a current from said source can flow through both said electrode means at a level which is a function of such consumption; said second electrode means and said medium being such that with the combination substantially only said species is elec-trolytically generable at said second electrode means at said current level, said second electrode means being biased by said power source at a potential at which said species is generable from said medium; the improvement compri-sing, the positioning of said second electrode means with respect to said first electrode means so that said surfaces of said first electrode means is interleaved in side by side relationship with said surfaces of said second electrode means with said surfaces of said electrodes equidistant from said barrier means and the periodicity of said positioning sufficiently small with respect to the thickness and species permeability of both said barrier means and said medium so that the species generated at said second electrode is consumed at said first electrode without any substantial transfer of said species across the interface between said barrier means and said fluid.
19. An electrode assembly as set forth in Claim 18 in which said sur-faces of said first and second electrode means define a surface which is a flat plane.
20. An electrode assembly as set forth in Claim 18 in which said sur-faces of said first and second electrode means define a surface which is cylindrical.
21. An electrode assembly as set forth in Claim 19 in which said sur-faces of said first and second electrode means are formed by a plurality of thin metal film strips deposited on an insulating flat substrate so as to be closely spaced.
22. An electrode assembly as set forth in Claim 18 in which said elec-trolytic medium is a thin film of liquid electrolyte.
23, An electrode assembly as set forth in Claim 18 in which said elec-trolytic medium is a thin film of solid electrolyte.
24. An electrode assembly as set forth in Claim 18 which includes a reference electrode contacting said medium and spaced from said first and second electrode means.
25. An electrode assembly as set forth in Claim 18 in which said elec-trolytic medium is a solid polymer electrolyte; and said first and second electrode means are formed by narrow strips of thin metal film deposited on a flat insulating substrate.
26. An electrode assembly for measuring the concentration of a specific electrochemically active species in a fluid, said assembly comprising in combination: an electrolytic medium from which only said species is elec-trolytically generable, a first electrode means having surfaces that are in contact with said medium, barrier means for separating said electrolytic medium from said fluid and being selectively permeable to said species and in contact with said medium, an electrical power source connected for biasing said first electrode means at a potential at which said species in said electrolytic medium will be consumed at the surfaces of said first electrode means, second electrode means having surfaces in contact with said medium and connected to said power source for completing a circuit in which the current from said source can flow through both said electrode means at a level which is a function of such consumption, said second electrode means and said electrolytic medium being such that with the combination sub-stantially only said species is electrolytically generable at the surfaces of said second electrode means at said current level, said second electrode means being biased by said power source at a potential at which said species is generable from said medium; and said second electrode means being so positioned as to be interleaved with said first electrode means so that said interleaved electrode means are substantially everywhere equidistant from said barrier means with the periodicity of said electrode means being sufficiently small with respect to the thickness and species permeability of both said barrier means and said medium so that the species generated at said second electrode is consumed at said first electrode without any sub-stantial transfer of said species across the interface between said barrier means and said fluid with the quantity of said species being transferred be-tween said electrode means being dependent upon a tendency of said species to establish an equilibrium condition across said barrier means between the concentration of said species respectively in said electrolytic medium and in said fluid.
27. An electrode assembly for measuring the concentration of a specific electrochemically reducible gas in a fluid, said assembly comprising) in combination: a cathode electrode, an anode electrode, an electrolytic medium in contact with said cathode and said anode, barrier means for separating said fluid and said medium, said barrier means being selectively permeable to said gas, and in contact with said medium, an electrical power source connected to said cathode for establishing a cathodic potential at said cathode electrode, said cathode being adapted for reducing said gas in said medium at said cathodic potential, said source providing an electrical current flow at said cathode at a level which is a function of such re-duction, said medium being a medium from which only said gas is electro-lytically generable at said anode at said current level, said anode being adapted for generating said gas from said medium at said current level and connected to said power source so as to complete a circuit between said anode and cathode and bias said anode at an anodic potential at which said gas can be generated from said medium, and said anode and cathode being positioned so that they are interleaved in side by side relationship with respect to one another and are everywhere equidistant from said barrier with a periodicity sufficiently small with respect to the thickness and the permeability to said gas of both said barrier means and said medium so that the gas generated at said anode is available for reduction at said cathode without any substantial transfer across the interface between said barrier means and said fluid and said potentials are established at magnitudes such that said current flow tends to substantially steady state condition res-ponsively to a tendency for an equilibrium condition to be established across said barrier means between the partial pressures of said gas in said medium and said fluid.
28. An electrode assembly for measuring the concentration of a specific electrochemically active gas in a fluid according to the level of electrical current flowing at a polarographic cathode responsive to the availability at said cathode of said gas; said assembly comprising in combination; a liquid medium electrically and anodically decomposable to generate said gas, barrier means for separating said fluid from said medium and being selectively per-meable to said gas and in contact with said medium, said polarographic cath-ode in contact with said medium for electrically consuming said gas, an anode in contact with said medium for electrically generating said gas, said anode being positioned side by side in close interleaved relationship to said cathode and lying in the surface defined by said polarographic cathode with said defined surface being everywhere equidistant from said barrier means with the periodicity of positioning between said cathode and anode being sufficiently small with respect to the thickness and permeability to said gas of both said barrier means and said medium so that gas generated at said anode will be consumed at said cathode without any substantial trans-fer across the interface between said barrier means and said fluid, and means for impressing at said polarographic cathode a first potential which is above the polarization potential for said gas and at said anode a second potential which is above the decomposition potential for said medium, said first and second potentials providing a current flow at said anode when said gas is present at said cathode which current flow is equal and opposite to said current flow at said cathode so that said gas, as generated at said anode, is available for consumption at said cathode in quantity dependent upon a tendency of said gas to establish an equilibrium condition across said barrier means between the concentration of said gas respectively in said medium and said fluid.
29. An electrode assembly as set forth in claim 18 in which said spec-ies is oxygen.
30. An electrode assembly as set forth in claim 18 in which said spec-ies is chlorine.
31. The method of measuring the concentration of an electrochemically active species in a fluid comprising the steps of: immersing in said fluid an electrode assembly including; an electrolytic medium, barrier means selec-tively permeable to said species, first electrode means of material elec-trochemically inert to both said medium and said species and having sur-faces in contact with said medium, second electrode means of material electrochemically inert to both said medium and said species, said second electrode means having surfaces in contact with said medium, means for supporting said first and second electrode means to position their respective surfaces in contact with said medium in an interleaved side by side relation-ship with said surfaces equidistant from said barrier means and positioned so that the periodicitiy of the spacing of said electrode surfaces is sufficiently small with respect to the thickness and species permeability of both said barrier means and said medium so that the species generated at the surfaces of said second electrode is consumed at the adjacent surfaces of said first electrode without any substantial transfer of said species across the interface between said barrier means and said fluid, and means connecting said first and second electrodes to a power source operable to bias said first and second electrodes at potentials to produce a current between said electrodes such that said species will be generated at said second electrode and consumed at said first electrode in quantity depen-dent upon the tendency of said species to establish an equilibrium condi-tion across said barrier means between the respective concentrations of said species in said medium and said fluid; and measuring said current flow as an indication of said species concentration in said fluid.
32. In an electrode assembly for measuring the concentration of a specific electrochemically active species in a fluid of the type which in-cludes in combination: an electrolytic medium; first electrode means of a noble metal material having surfaces in contact with said medium; barrier means for separating said medium from said fluid, and being selectively perm-eable to said species, and in contact with said medium; an electrical power .
source connected for biasing said first electrode means at a potential at which said species in said medium will be consumed at said surfaces of said first electrode means; second electrode means of a noble metal material, said second electrode means being in contact with said medium and connected to said power source for completing a circuit in which a current from said source can flow through both said electrode means at a level which is a function of such consumption; said medium being one from which substantially only said species is electrolytically generable at said second electrode means at said current level, said second electrode means being biased by said power source at a potential at which said species is generable from said medium; and said second electrode means being so positioned with respect to said first electrode means and said barrier means that said species as generated at said second electrode means is available for consumption at said first electrode means in quantity dependent upon a tendency of said species to establish and equilibrium condition across said barrier means be-tween concentration of said species respectively in said electrolyte and in said fluid; the improvement comprising, the positioning of said second electrode means with respect to said first electrode means so that said first electrode means is interleaved in side by side relationship with said second electrode means with said electrodes equidistant from said barrier means.
source connected for biasing said first electrode means at a potential at which said species in said medium will be consumed at said surfaces of said first electrode means; second electrode means of a noble metal material, said second electrode means being in contact with said medium and connected to said power source for completing a circuit in which a current from said source can flow through both said electrode means at a level which is a function of such consumption; said medium being one from which substantially only said species is electrolytically generable at said second electrode means at said current level, said second electrode means being biased by said power source at a potential at which said species is generable from said medium; and said second electrode means being so positioned with respect to said first electrode means and said barrier means that said species as generated at said second electrode means is available for consumption at said first electrode means in quantity dependent upon a tendency of said species to establish and equilibrium condition across said barrier means be-tween concentration of said species respectively in said electrolyte and in said fluid; the improvement comprising, the positioning of said second electrode means with respect to said first electrode means so that said first electrode means is interleaved in side by side relationship with said second electrode means with said electrodes equidistant from said barrier means.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/730,409 US4076596A (en) | 1976-10-07 | 1976-10-07 | Apparatus for electrolytically determining a species in a fluid and method of use |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1074867A true CA1074867A (en) | 1980-04-01 |
Family
ID=24935227
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA288,245A Expired CA1074867A (en) | 1976-10-07 | 1977-10-06 | Apparatus for electrolytically determining a species in a fluid |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4076596A (en) |
| JP (1) | JPS5346087A (en) |
| CA (1) | CA1074867A (en) |
| DE (1) | DE2744771A1 (en) |
| GB (1) | GB1558251A (en) |
| IT (1) | IT1088960B (en) |
Families Citing this family (139)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4228400A (en) * | 1978-03-28 | 1980-10-14 | Research Corporation | Conductometric gas analysis cell |
| US4168220A (en) * | 1978-07-10 | 1979-09-18 | Leeds & Northrup Company | Method for detecting the fouling of a membrane covered electrochemical cell |
| US4473456A (en) * | 1981-04-08 | 1984-09-25 | National Research Development Corporation | Conductimetric gas sensor |
| US4571292A (en) * | 1982-08-12 | 1986-02-18 | Case Western Reserve University | Apparatus for electrochemical measurements |
| US4450064A (en) * | 1983-03-21 | 1984-05-22 | Beckman Instruments, Inc. | Electrochemical gas sensor and method for producing the same |
| US4457808A (en) * | 1983-05-16 | 1984-07-03 | General Signal Corporation | Method and means for recalibrating electrochemical cells in situ |
| US4459180A (en) * | 1983-05-16 | 1984-07-10 | General Signal Corporation | Method and means for compensating for IR voltage drop in electrochemical cells |
| US4655880A (en) * | 1983-08-01 | 1987-04-07 | Case Western Reserve University | Apparatus and method for sensing species, substances and substrates using oxidase |
| DE3474216D1 (en) * | 1984-02-20 | 1988-10-27 | Yokogawa Electrofact Bv | Electrode assembly for measuring the concentration of an electro-chemical active species |
| DE3429583A1 (en) * | 1984-08-10 | 1986-02-20 | Siemens AG, 1000 Berlin und 8000 München | METHOD FOR ELECTROCHEMICALLY DETERMINING THE OXYGEN CONCENTRATION |
| GB8500813D0 (en) * | 1985-01-14 | 1985-02-20 | Bergman I | Electrochemical sensor |
| DE3504498A1 (en) * | 1985-02-09 | 1986-08-14 | Drägerwerk AG, 2400 Lübeck | GAS SENSOR WITH SEVERAL SENSOR ELEMENTS |
| EP0205399B1 (en) * | 1985-06-10 | 1993-10-06 | ORBISPHERE CORPORATION Wilmington Succursale de Collonge-Bellerive | Amperometric cell and method |
| JPS62107772U (en) * | 1985-12-26 | 1987-07-09 | ||
| US4822474A (en) * | 1987-04-30 | 1989-04-18 | Pennwalt Corporation | Residual analyzer assembly |
| US4925544A (en) * | 1987-05-15 | 1990-05-15 | National Research Development Corporation | Electrochemical sensor with solid phase electrolyte |
| CA1279896C (en) * | 1987-05-26 | 1991-02-05 | Joseph R. Stetter | Eletrochemical micro sensor |
| US4865717A (en) * | 1987-05-26 | 1989-09-12 | Transducer Research, Inc. | Electrochemical micro sensor |
| US4795543A (en) * | 1987-05-26 | 1989-01-03 | Transducer Research, Inc. | Spin coating of electrolytes |
| US4812221A (en) * | 1987-07-15 | 1989-03-14 | Sri International | Fast response time microsensors for gaseous and vaporous species |
| US4900405A (en) * | 1987-07-15 | 1990-02-13 | Sri International | Surface type microelectronic gas and vapor sensor |
| US4913792A (en) * | 1987-07-28 | 1990-04-03 | Daikin Industries, Ltd. | Flammable-gas sensor |
| US4789436A (en) * | 1988-02-22 | 1988-12-06 | The United States Of America As Represented By The United States Department Of Energy | Method and apparatus for nondestructive in vivo measurement of photosynthesis |
| WO1990015323A1 (en) * | 1989-06-02 | 1990-12-13 | Sri International | Surface type microelectronic gas and vapor sensor |
| JPH03183943A (en) * | 1989-12-14 | 1991-08-09 | Hitachi Ltd | Oxygen sensor |
| DE4014109A1 (en) * | 1990-05-02 | 1991-11-07 | Siemens Ag | ELECROCHEMICAL DETERMINATION OF THE OXYGEN CONCENTRATION |
| EP0465708B1 (en) * | 1990-07-11 | 1996-05-22 | Siemens Aktiengesellschaft | Device for electrochemically determining the partial pressure of oxygen in a liquid and method for operating the device |
| US5246576A (en) * | 1990-12-10 | 1993-09-21 | Ppg Industries, Inc. | Cathode in a layered circuit and electrochemical cell for a measurement of oxygen in fluids |
| JPH04278450A (en) * | 1991-03-04 | 1992-10-05 | Adam Heller | Biosensor and method for analyzing subject |
| US5593852A (en) | 1993-12-02 | 1997-01-14 | Heller; Adam | Subcutaneous glucose electrode |
| GB2258535A (en) * | 1991-08-03 | 1993-02-10 | British Aerospace | Corrosion sensors |
| FR2701117B1 (en) * | 1993-02-04 | 1995-03-10 | Asulab Sa | Electrochemical measurement system with multizone sensor, and its application to glucose measurement. |
| US5387329A (en) * | 1993-04-09 | 1995-02-07 | Ciba Corning Diagnostics Corp. | Extended use planar sensors |
| DE4335487C2 (en) * | 1993-10-18 | 2003-12-18 | St Jude Medical | oxygen sensor |
| GB2292805B (en) * | 1994-08-26 | 1998-09-09 | Mil Ram Techn Inc | Method and apparatus for the detection of toxic gases |
| US6413410B1 (en) * | 1996-06-19 | 2002-07-02 | Lifescan, Inc. | Electrochemical cell |
| US6863801B2 (en) * | 1995-11-16 | 2005-03-08 | Lifescan, Inc. | Electrochemical cell |
| US6638415B1 (en) | 1995-11-16 | 2003-10-28 | Lifescan, Inc. | Antioxidant sensor |
| AUPN661995A0 (en) | 1995-11-16 | 1995-12-07 | Memtec America Corporation | Electrochemical cell 2 |
| US6632349B1 (en) * | 1996-11-15 | 2003-10-14 | Lifescan, Inc. | Hemoglobin sensor |
| ATE227844T1 (en) | 1997-02-06 | 2002-11-15 | Therasense Inc | SMALL VOLUME SENSOR FOR IN-VITRO DETERMINATION |
| AUPO855897A0 (en) | 1997-08-13 | 1997-09-04 | Usf Filtration And Separations Group Inc. | Automatic analysing apparatus II |
| US6103033A (en) * | 1998-03-04 | 2000-08-15 | Therasense, Inc. | Process for producing an electrochemical biosensor |
| US6134461A (en) * | 1998-03-04 | 2000-10-17 | E. Heller & Company | Electrochemical analyte |
| US6878251B2 (en) * | 1998-03-12 | 2005-04-12 | Lifescan, Inc. | Heated electrochemical cell |
| US6475360B1 (en) | 1998-03-12 | 2002-11-05 | Lifescan, Inc. | Heated electrochemical cell |
| US9066695B2 (en) | 1998-04-30 | 2015-06-30 | Abbott Diabetes Care Inc. | Analyte monitoring device and methods of use |
| US6949816B2 (en) * | 2003-04-21 | 2005-09-27 | Motorola, Inc. | Semiconductor component having first surface area for electrically coupling to a semiconductor chip and second surface area for electrically coupling to a substrate, and method of manufacturing same |
| US8974386B2 (en) | 1998-04-30 | 2015-03-10 | Abbott Diabetes Care Inc. | Analyte monitoring device and methods of use |
| US6175752B1 (en) | 1998-04-30 | 2001-01-16 | Therasense, Inc. | Analyte monitoring device and methods of use |
| US8465425B2 (en) | 1998-04-30 | 2013-06-18 | Abbott Diabetes Care Inc. | Analyte monitoring device and methods of use |
| US8480580B2 (en) | 1998-04-30 | 2013-07-09 | Abbott Diabetes Care Inc. | Analyte monitoring device and methods of use |
| US8346337B2 (en) | 1998-04-30 | 2013-01-01 | Abbott Diabetes Care Inc. | Analyte monitoring device and methods of use |
| US8688188B2 (en) | 1998-04-30 | 2014-04-01 | Abbott Diabetes Care Inc. | Analyte monitoring device and methods of use |
| US6251260B1 (en) | 1998-08-24 | 2001-06-26 | Therasense, Inc. | Potentiometric sensors for analytic determination |
| US6338790B1 (en) * | 1998-10-08 | 2002-01-15 | Therasense, Inc. | Small volume in vitro analyte sensor with diffusible or non-leachable redox mediator |
| US6591125B1 (en) | 2000-06-27 | 2003-07-08 | Therasense, Inc. | Small volume in vitro analyte sensor with diffusible or non-leachable redox mediator |
| EP1192269A2 (en) | 1999-06-18 | 2002-04-03 | Therasense, Inc. | MASS TRANSPORT LIMITED i IN VIVO /i ANALYTE SENSOR |
| US20060091006A1 (en) * | 1999-11-04 | 2006-05-04 | Yi Wang | Analyte sensor with insertion monitor, and methods |
| US6616819B1 (en) * | 1999-11-04 | 2003-09-09 | Therasense, Inc. | Small volume in vitro analyte sensor and methods |
| RU2278612C2 (en) * | 2000-07-14 | 2006-06-27 | Лайфскен, Инк. | Immune sensor |
| US6444115B1 (en) | 2000-07-14 | 2002-09-03 | Lifescan, Inc. | Electrochemical method for measuring chemical reaction rates |
| US6560471B1 (en) | 2001-01-02 | 2003-05-06 | Therasense, Inc. | Analyte monitoring device and methods of use |
| EP1397068A2 (en) | 2001-04-02 | 2004-03-17 | Therasense, Inc. | Blood glucose tracking apparatus and methods |
| US20020166776A1 (en) * | 2001-05-10 | 2002-11-14 | Axel Fikus | Electrochemical gas sensor |
| US6808618B2 (en) * | 2001-07-25 | 2004-10-26 | Joseph Robert Stetter | Chemical sensing apparatus and methods |
| RU2297696C2 (en) * | 2001-10-10 | 2007-04-20 | Лайфскен, Инк. | Electrochemical cell |
| US6761817B2 (en) | 2001-12-19 | 2004-07-13 | Honeywell International Inc. | Smart determination of dissolved oxygen probe operating bias |
| US20060134713A1 (en) * | 2002-03-21 | 2006-06-22 | Lifescan, Inc. | Biosensor apparatus and methods of use |
| US20030180814A1 (en) * | 2002-03-21 | 2003-09-25 | Alastair Hodges | Direct immunosensor assay |
| US7381184B2 (en) | 2002-11-05 | 2008-06-03 | Abbott Diabetes Care Inc. | Sensor inserter assembly |
| EP2314691A3 (en) * | 2002-11-14 | 2012-01-18 | Dharmacon, Inc. | Fuctional and hyperfunctional siRNA |
| AU2003303597A1 (en) | 2002-12-31 | 2004-07-29 | Therasense, Inc. | Continuous glucose monitoring system and methods of use |
| US8066639B2 (en) | 2003-06-10 | 2011-11-29 | Abbott Diabetes Care Inc. | Glucose measuring device for use in personal area network |
| US7306641B2 (en) * | 2003-09-12 | 2007-12-11 | Hewlett-Packard Development Company, L.P. | Integral fuel cartridge and filter |
| USD914881S1 (en) | 2003-11-05 | 2021-03-30 | Abbott Diabetes Care Inc. | Analyte sensor electronic mount |
| EP1718198A4 (en) | 2004-02-17 | 2008-06-04 | Therasense Inc | Method and system for providing data communication in continuous glucose monitoring and management system |
| US8613703B2 (en) | 2007-05-31 | 2013-12-24 | Abbott Diabetes Care Inc. | Insertion devices and methods |
| US9743862B2 (en) | 2011-03-31 | 2017-08-29 | Abbott Diabetes Care Inc. | Systems and methods for transcutaneously implanting medical devices |
| US20070027381A1 (en) * | 2005-07-29 | 2007-02-01 | Therasense, Inc. | Inserter and methods of use |
| US10226207B2 (en) | 2004-12-29 | 2019-03-12 | Abbott Diabetes Care Inc. | Sensor inserter having introducer |
| US8512243B2 (en) | 2005-09-30 | 2013-08-20 | Abbott Diabetes Care Inc. | Integrated introducer and transmitter assembly and methods of use |
| US20110190603A1 (en) * | 2009-09-29 | 2011-08-04 | Stafford Gary A | Sensor Inserter Having Introducer |
| US9788771B2 (en) | 2006-10-23 | 2017-10-17 | Abbott Diabetes Care Inc. | Variable speed sensor insertion devices and methods of use |
| US9259175B2 (en) | 2006-10-23 | 2016-02-16 | Abbott Diabetes Care, Inc. | Flexible patch for fluid delivery and monitoring body analytes |
| US8571624B2 (en) * | 2004-12-29 | 2013-10-29 | Abbott Diabetes Care Inc. | Method and apparatus for mounting a data transmission device in a communication system |
| US9398882B2 (en) * | 2005-09-30 | 2016-07-26 | Abbott Diabetes Care Inc. | Method and apparatus for providing analyte sensor and data processing device |
| US7697967B2 (en) | 2005-12-28 | 2010-04-13 | Abbott Diabetes Care Inc. | Method and apparatus for providing analyte sensor insertion |
| US20110060196A1 (en) * | 2009-08-31 | 2011-03-10 | Abbott Diabetes Care Inc. | Flexible Mounting Unit and Cover for a Medical Device |
| US8333714B2 (en) | 2006-09-10 | 2012-12-18 | Abbott Diabetes Care Inc. | Method and system for providing an integrated analyte sensor insertion device and data processing unit |
| US9572534B2 (en) | 2010-06-29 | 2017-02-21 | Abbott Diabetes Care Inc. | Devices, systems and methods for on-skin or on-body mounting of medical devices |
| US20110054275A1 (en) * | 2009-08-31 | 2011-03-03 | Abbott Diabetes Care Inc. | Mounting Unit Having a Sensor and Associated Circuitry |
| US7883464B2 (en) | 2005-09-30 | 2011-02-08 | Abbott Diabetes Care Inc. | Integrated transmitter unit and sensor introducer mechanism and methods of use |
| US20090105569A1 (en) | 2006-04-28 | 2009-04-23 | Abbott Diabetes Care, Inc. | Introducer Assembly and Methods of Use |
| US7731657B2 (en) | 2005-08-30 | 2010-06-08 | Abbott Diabetes Care Inc. | Analyte sensor introducer and methods of use |
| US20060175208A1 (en) * | 2005-02-09 | 2006-08-10 | Eickhoff Steven J | Water-conductivity CO2 sensor |
| US8112240B2 (en) | 2005-04-29 | 2012-02-07 | Abbott Diabetes Care Inc. | Method and apparatus for providing leak detection in data monitoring and management systems |
| US9521968B2 (en) * | 2005-09-30 | 2016-12-20 | Abbott Diabetes Care Inc. | Analyte sensor retention mechanism and methods of use |
| US7766829B2 (en) | 2005-11-04 | 2010-08-03 | Abbott Diabetes Care Inc. | Method and system for providing basal profile modification in analyte monitoring and management systems |
| US11298058B2 (en) | 2005-12-28 | 2022-04-12 | Abbott Diabetes Care Inc. | Method and apparatus for providing analyte sensor insertion |
| CA2636034A1 (en) * | 2005-12-28 | 2007-10-25 | Abbott Diabetes Care Inc. | Medical device insertion |
| US7885698B2 (en) | 2006-02-28 | 2011-02-08 | Abbott Diabetes Care Inc. | Method and system for providing continuous calibration of implantable analyte sensors |
| US8226891B2 (en) | 2006-03-31 | 2012-07-24 | Abbott Diabetes Care Inc. | Analyte monitoring devices and methods therefor |
| US7620438B2 (en) | 2006-03-31 | 2009-11-17 | Abbott Diabetes Care Inc. | Method and system for powering an electronic device |
| US7920907B2 (en) | 2006-06-07 | 2011-04-05 | Abbott Diabetes Care Inc. | Analyte monitoring system and method |
| GB0616566D0 (en) * | 2006-08-19 | 2006-09-27 | Rolls Royce Plc | An alloy and method of treating titanium aluminide |
| US8930203B2 (en) | 2007-02-18 | 2015-01-06 | Abbott Diabetes Care Inc. | Multi-function analyte test device and methods therefor |
| US8732188B2 (en) | 2007-02-18 | 2014-05-20 | Abbott Diabetes Care Inc. | Method and system for providing contextual based medication dosage determination |
| US8123686B2 (en) | 2007-03-01 | 2012-02-28 | Abbott Diabetes Care Inc. | Method and apparatus for providing rolling data in communication systems |
| US8665091B2 (en) | 2007-05-08 | 2014-03-04 | Abbott Diabetes Care Inc. | Method and device for determining elapsed sensor life |
| US8456301B2 (en) | 2007-05-08 | 2013-06-04 | Abbott Diabetes Care Inc. | Analyte monitoring system and methods |
| US8461985B2 (en) | 2007-05-08 | 2013-06-11 | Abbott Diabetes Care Inc. | Analyte monitoring system and methods |
| US7928850B2 (en) | 2007-05-08 | 2011-04-19 | Abbott Diabetes Care Inc. | Analyte monitoring system and methods |
| EP2163190A1 (en) | 2008-09-11 | 2010-03-17 | Roche Diagnostics GmbH | Electrode system for measurement of an analyte concentration in-vivo |
| US8103456B2 (en) | 2009-01-29 | 2012-01-24 | Abbott Diabetes Care Inc. | Method and device for early signal attenuation detection using blood glucose measurements |
| US20100198034A1 (en) * | 2009-02-03 | 2010-08-05 | Abbott Diabetes Care Inc. | Compact On-Body Physiological Monitoring Devices and Methods Thereof |
| US20100213057A1 (en) * | 2009-02-26 | 2010-08-26 | Benjamin Feldman | Self-Powered Analyte Sensor |
| US9226701B2 (en) | 2009-04-28 | 2016-01-05 | Abbott Diabetes Care Inc. | Error detection in critical repeating data in a wireless sensor system |
| WO2010138856A1 (en) | 2009-05-29 | 2010-12-02 | Abbott Diabetes Care Inc. | Medical device antenna systems having external antenna configurations |
| WO2011025999A1 (en) * | 2009-08-29 | 2011-03-03 | Abbott Diabetes Care Inc. | Analyte sensor |
| WO2011026148A1 (en) | 2009-08-31 | 2011-03-03 | Abbott Diabetes Care Inc. | Analyte monitoring system and methods for managing power and noise |
| US20110106126A1 (en) * | 2009-08-31 | 2011-05-05 | Michael Love | Inserter device including rotor subassembly |
| WO2011026147A1 (en) | 2009-08-31 | 2011-03-03 | Abbott Diabetes Care Inc. | Analyte signal processing device and methods |
| US9320461B2 (en) | 2009-09-29 | 2016-04-26 | Abbott Diabetes Care Inc. | Method and apparatus for providing notification function in analyte monitoring systems |
| WO2011041531A1 (en) | 2009-09-30 | 2011-04-07 | Abbott Diabetes Care Inc. | Interconnect for on-body analyte monitoring device |
| WO2011044386A1 (en) * | 2009-10-07 | 2011-04-14 | Abbott Diabetes Care Inc. | Sensor inserter assembly having rotatable trigger |
| USD924406S1 (en) | 2010-02-01 | 2021-07-06 | Abbott Diabetes Care Inc. | Analyte sensor inserter |
| CA3135001A1 (en) | 2010-03-24 | 2011-09-29 | Abbott Diabetes Care Inc. | Medical device inserters and processes of inserting and using medical devices |
| US11064921B2 (en) | 2010-06-29 | 2021-07-20 | Abbott Diabetes Care Inc. | Devices, systems and methods for on-skin or on-body mounting of medical devices |
| JP6443802B2 (en) | 2011-11-07 | 2018-12-26 | アボット ダイアベティス ケア インコーポレイテッドＡｂｂｏｔｔ Ｄｉａｂｅｔｅｓ Ｃａｒｅ Ｉｎｃ． | Analyte monitoring apparatus and method |
| EP4344633A2 (en) | 2011-12-11 | 2024-04-03 | Abbott Diabetes Care, Inc. | Analyte sensor methods |
| US9968306B2 (en) | 2012-09-17 | 2018-05-15 | Abbott Diabetes Care Inc. | Methods and apparatuses for providing adverse condition notification with enhanced wireless communication range in analyte monitoring systems |
| US20140361031A1 (en) * | 2013-06-11 | 2014-12-11 | Parata Systems, Llc | Methods and apparatus for dispensing solid pharmaceutical articles using capacitive level sensors |
| ITMI20131096A1 (en) * | 2013-06-28 | 2014-12-29 | St Microelectronics Srl | INTEGRATED GAS SENSOR DEVICE, IN PARTICULAR FOR THE DETECTION OF CARBON MONOXIDE (CO) |
| US10213139B2 (en) | 2015-05-14 | 2019-02-26 | Abbott Diabetes Care Inc. | Systems, devices, and methods for assembling an applicator and sensor control device |
| WO2016183493A1 (en) | 2015-05-14 | 2016-11-17 | Abbott Diabetes Care Inc. | Compact medical device inserters and related systems and methods |
| US9612700B2 (en) * | 2015-07-31 | 2017-04-04 | Haier Us Appliance Solutions, Inc. | User interface assemblies and electrode assemblies having intertwined electrodes |
| EP3359959A1 (en) * | 2015-10-09 | 2018-08-15 | Hach Company | Membrane-based water quality sensor |
| CN115444410A (en) | 2017-01-23 | 2022-12-09 | 雅培糖尿病护理公司 | Applicator and assembly for inserting an in vivo analyte sensor |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL92243C (en) * | 1950-05-17 | |||
| US2913386A (en) * | 1956-03-21 | 1959-11-17 | Jr Leland C Clark | Electrochemical device for chemical analysis |
| US3000805A (en) * | 1957-08-30 | 1961-09-19 | Walter G Finch | Electrode measuring device |
| US3240693A (en) * | 1961-08-28 | 1966-03-15 | Beckman Instruments Inc | Hygrometer |
| US3223609A (en) * | 1961-10-30 | 1965-12-14 | Beckman Instruments Inc | Hygrometer |
| US3260656A (en) * | 1962-09-27 | 1966-07-12 | Corning Glass Works | Method and apparatus for electrolytically determining a species in a fluid |
| US3337441A (en) * | 1963-08-19 | 1967-08-22 | Atomic Energy Authority Uk | Phosphoric acid-glycerine electrolyte for hygroscopic cell |
| US3474022A (en) * | 1967-09-14 | 1969-10-21 | Atomic Energy Commission | Alarm system for uf6 in air |
| US3719575A (en) * | 1970-10-15 | 1973-03-06 | Gen Electric | Sensor with ion exchange resin electrolyte |
| FR2147344A5 (en) * | 1970-12-31 | 1973-03-09 | Hoffmann La Roche | |
| FR2245248A5 (en) * | 1973-09-20 | 1975-04-18 | Radiotechnique Compelec |
-
1976
- 1976-10-07 US US05/730,409 patent/US4076596A/en not_active Expired - Lifetime
-
1977
- 1977-09-30 GB GB40772/77A patent/GB1558251A/en not_active Expired
- 1977-10-05 DE DE19772744771 patent/DE2744771A1/en not_active Ceased
- 1977-10-06 CA CA288,245A patent/CA1074867A/en not_active Expired
- 1977-10-06 JP JP11955577A patent/JPS5346087A/en active Granted
- 1977-10-07 IT IT7728376A patent/IT1088960B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| DE2744771A1 (en) | 1978-04-13 |
| US4076596A (en) | 1978-02-28 |
| GB1558251A (en) | 1979-12-19 |
| IT1088960B (en) | 1985-06-10 |
| JPS5346087A (en) | 1978-04-25 |
| JPS5651582B2 (en) | 1981-12-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1074867A (en) | Apparatus for electrolytically determining a species in a fluid | |
| US3260656A (en) | Method and apparatus for electrolytically determining a species in a fluid | |
| Dietz | Gas-diffusion-controlled solid-electrolyte oxygen sensors | |
| Gyurcsányi et al. | Microfabricated ISEs: critical comparison of inherently conducting polymer and hydrogel based inner contacts | |
| US3719564A (en) | Method of determining a reducible gas concentration and sensor therefor | |
| US4900405A (en) | Surface type microelectronic gas and vapor sensor | |
| US20050072690A1 (en) | Ion exchange membranes and dissolved gas sensors | |
| EP0064337B1 (en) | Carbon dioxide measurement | |
| JPH0781984B2 (en) | Sensor structure | |
| US4367133A (en) | Electrochemical gas analyzer | |
| Glasspool et al. | A screen-printed amperometric dissolved oxygen sensor utilising an immobilised electrolyte gel and membrane | |
| US20030089623A1 (en) | Chemical sensor | |
| JPS6142821B2 (en) | ||
| JPH02297054A (en) | Electrochemical measuring cell for measuring ammonia or hydrazine in gaseous or liquid measuring sample | |
| EP0805976B1 (en) | Electrochemical planar metal/metal oxide electrode | |
| US5322601A (en) | Amperometric gas sensor to selectively determine the partial pressures of a gas | |
| US6129824A (en) | Electrochemical sensor for the detection of hydrogen chloride | |
| US4469562A (en) | Carbon dioxide sensor | |
| CA1116696A (en) | Ion-selective electrode | |
| JP2943028B2 (en) | pH measuring electrode and method for producing the same | |
| GB2025625A (en) | Method for detectin the fouling of a membrane-covered electrochemical cell | |
| AU1958088A (en) | Electrochemical micro sensor | |
| Katakura et al. | An oxygen sensor composed of tightly stacked membrane/electrode/electrolyte. | |
| Mari et al. | Electrochemical gas sensors | |
| EP1288655A2 (en) | Gas sensor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |