EP1038172A1 - Dispositifs de detection et procede d'analyse - Google Patents

Dispositifs de detection et procede d'analyse

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Publication number
EP1038172A1
EP1038172A1 EP98959014A EP98959014A EP1038172A1 EP 1038172 A1 EP1038172 A1 EP 1038172A1 EP 98959014 A EP98959014 A EP 98959014A EP 98959014 A EP98959014 A EP 98959014A EP 1038172 A1 EP1038172 A1 EP 1038172A1
Authority
EP
European Patent Office
Prior art keywords
electrode
analyte
sample
ion
detecting electrode
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.)
Withdrawn
Application number
EP98959014A
Other languages
German (de)
English (en)
Inventor
Pankaj Madganlal Vadgama
Ian Mcintyre Christie
Peter Barrington Long
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Victoria University of Manchester
University of Manchester
Original Assignee
Victoria University of Manchester
University of Manchester
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from GB9726230A external-priority patent/GB2332278A/en
Priority claimed from GBGB9816909.7A external-priority patent/GB9816909D0/en
Application filed by Victoria University of Manchester, University of Manchester filed Critical Victoria University of Manchester
Publication of EP1038172A1 publication Critical patent/EP1038172A1/fr
Withdrawn legal-status Critical Current

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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
    • G01N27/4035—Combination of a single ion-sensing electrode and a single reference electrode

Definitions

  • TITLE SENSOR DEVICES AND ANALYTICAL METHOD.
  • This invention relates to sensor devices and more particularly to electrochemical sensor devices, and to analytical methods using them.
  • ISE ion-selective electrode
  • the reference electrode assembly usually employs a liquid junction between (a) the sample and (b) the reference electrode and its associated internal electrolyte. The liquid junction maintains electrical continuity in the electrochemical cell while restricting contamination of the inner electrolyte of the reference electrode assembly by the sample.
  • potentiometric measurements are made based on redox reactions at electrodes, preferably metals such as platinum and gold.
  • electrodes preferably metals such as platinum and gold.
  • a reference electrode is required for these measurements, and both the redox and the reference electrode assemblies should contact the sample.
  • the known methods and devices for using detecting electrodes such as an ISE or redox electrode for detection and/or measurement purposes are all based on the simple procedure of putting both the detecting electrode and the liquid junction of the reference electrode assembly in contact with the sample, and then measuring the electrical potential between the detecting electrode and the reference electrode. Appropriate analytical conclusions are drawn from the measurements of this potential, e.g. by comparison with the potential generated when standard solutions are used.
  • the known devices and systems have been found to suffer from disadvantages so that they are not entirely satisfactory in use, because the standard modes for using them require careful calibration against standards and also stabilisation before they can give accurate or reliable results .
  • Proposals have been made for various forms of active electrode which are covered or surrounded by a membrane, as a feature which can serve to protect the electrode from physical damage or, more commonly, to retain a controlled internal electrolyte or liquid film or to confer other selective control over how the different components from a sample can gain access to the electrode.
  • Such control is often needed when a sample under examination contains compounds which can interfere seriously with the detection of desired analytes at the electrode - sometimes by behaving similarly to the analyte and sometimes by deactivating (fouling) the electrode so that it ceases to function properly.
  • This selectivity can act in several ways, but with the aim of holding back an undesirable interfering component while the desired analyte can pass on towards the detecting electrode.
  • a reactive component which may either destroy the undesirable interferents or convert the desired component into another compound which is more readily able to reach the electrode and be determined there.
  • An example is an enzyme electrode, particularly one in which glucose oxidase is used to catalyse the oxidation of glucose to form by-product hydrogen peroxide which readily passes on to the electrode.
  • membrane barriers are regarded as a necessary nuisance that slows up responses when rapid response and equilibrium are wanted.
  • ISEs operate in a very different way, as they generate the voltage to be measured and normally respond within milliseconds to seconds, and the desired baseline can be almost anywhere in terms of any measurable mV values. Therefore satisfactory measurements with such electrodes can be made very difficult by this phenomenon, termed "baseline drift.”
  • a membrane which is not selective in favour of a desired analyte, and may even slow up access of the desired analyte to the electrode.
  • This is novel and in contrast to the known methods of using membranes, where the membrane is acts in the opposite manner and is used to impede the access of undesirable interferents without impeding the access of desired analyte.
  • a sensor system using a permeable barrier e.g. a membrane in this novel way can enable an analyte to be determined very much more readily, by measuring the rate of change of output signal from the detecting electrode, which is caused by the regulated diffusion of the analyte through the membrane.
  • ISEs in particular have so far been used only in bare form, without a covering membrane, so the covering technique is new - especially for an ISE and, we believe, for other detecting electrodes too. It offers the further advantages that the signal from the electrode may not need to fully reach equilibrium, and of being applicable to any other electrode which functions in a non-amperometric manner.
  • the difficulties can be overcome by covering the detecting electrode with a permeable barrier of restricted permeability which then interfaces with the sample, so that the sample itself no longer provides the sole bridging contact between the detecting electrode and reference electrode assembly to complete the measuring circuit.
  • This permeable barrier allows the system to operate by diffusion of components, between the sample and the region within the permeable barrier, before the output signals from the electrodes are measured and such measurements are used as a basis for the determination of the composition of the sample.
  • the permeable barrier covers at least the detecting electrode, and preferably both the detecting electrode and the reference electrode assembly.
  • a sensor system comprising a detecting electrode and a reference electrode in combination, characterised in that the detecting electrode is enclosed within a permeable barrier adapted to interface with a sample under examination, so that the sample itself no longer provides the main bridging contact between the detecting and reference electrodes to complete the measuring circuit .
  • both the detecting electrode and the reference electrode are enclosed within the same permeable barrier to separate them from the sample .
  • a sensor device comprising a detecting electrode and a reference electrode in combination, characterised in that these are both enclosed within a permeable barrier adapted to interface with a sample under examination, so that the sample itself no longer provides the main bridging contact between the detecting electrode and the reference electrode to complete the measuring circuit .
  • Our invention also provides an improved method for the determination of an analyte in a sample, which comprises using a sensor device with an ion-selective electrode or redox electrode and a reference electrode assembly in combination as described herein.
  • a permeable barrier adapted to interface with a sample under examination, so that the sample itself no longer provides the main bridging contact between the detecting and reference electrodes to complete the measuring circuit, measuring the potential between the detecting electrode and the reference electrode and using this measure for determining the content of the analyte .
  • the two types of electrode used are well-known and are amply described in the literature. Their precise form and construction are not critical but the following summary assists in describing them.
  • the reference electrode may be any of those known or used in the art .
  • the preferred and most convenient form of reference electrode assembly comprises a conventional half- cell containing a silver/silver chloride (Ag/AgCl) or calomel electrode system, with its conventional filling solution (usually an electrolyte) , enclosed in a container which has a "liquid junction", “salt bridge” or “double junction” arrangement customarily intended to make contact with the sample.
  • This "liquid junction” is commonly a porous membrane which serves to allow the necessary electrical conductivity to complete the electrical measuring circuit while restricting flow and/or diffusion of the sample or its components into the reference cell or any outward flow to contaminate the sample.
  • the presence of a further permeable barrier between the reference electrode and the sample, as in the present invention also provides a further safeguard against such contamination.
  • a Ag/AgCl electrode may be overlaid with a membrane of material such as polyvinyl alcohol, which readily hydrates and (in terms of the electrode potential) the arrangement is satisfactorily stable, especially when the electrode is required for only a short measurement duration.
  • the detecting electrode for use in our invention may be any of those known or used in the art for detecting analytes by producing output signals representative of a component or characteristic which can provide a measure of the analyte present in a sample under examination.
  • the preferred detecting electrode is one which is not normally used in an amperometric measuring mode, and the signal output (potential) is preferably measured by a non- amperometric method.
  • it may be an ion-selective electrode
  • ISE for example a conventional ion-selective electrode with an internal electrolyte and an internal reference
  • detecting electrode e.g. Ag/AgCl
  • coated wire electrode where a base metal wire is in direct contact with a covering ion- selective membrane.
  • the invention is applicable to a variety of alternative forms of detecting electrode, for example redox electrodes, and is not limited only to use for ISE devices.
  • the ISE response is a potential change across a membrane or coating
  • the ISE assembly includes this layer and an internal electrode, covered or enclosed by the coating or membrane material having the ion-sensitive or ion-selective properties.
  • This coating or membrane surface interacts with the ionic components from a sample to generate a measuring voltage (EMF) and may allow preferential interaction or passage of those ions which it is desired to measure.
  • EMF measuring voltage
  • the internal electrode may be a conventional one capable of use for measurement of electrochemical potentials such as Ag/AgCl but may also be, for example, metals such as platinum, gold, silver or copper (though others may be used if desired) as in coated wire electrodes.
  • coatings include those containing additive components which are ion-selective in the sense of having powers for ion-exchange, ion- adsorption, complex-forming neutral compounds or chelating ions, or the like, or combinations of such properties.
  • examples include liquid ion exchangers, neutral carriers and plasticisers (solvents) retained physically or incorporated into a polymer layer in any combination or singly.
  • the potential forms at the coating or membrane, or across it; the internal electrode is there simply to make a contact and, like the reference electrode, to be used to measure potential between two points either side of the membrane .
  • solid-state electrodes may be used without the need for an ion-selective coating if they already themselves possess the necessary ion-selective properties.
  • the ISE usually comprises a covering or layer (e.g. a membrane or a gel) over an internal core sensing electrode and the components imparting ion-sensitivity may be in or on the internal core sensing electrode and/or the said covering or layer.
  • a common form of ISE may contain, when in use, an inner medium (commonly an electrolyte) , which may conveniently be in liquid or gel form, and associated contacting electrodes .
  • the inner medium is usually aqueous but may be non-aqueous if desired, or contain a combination of aqueous and non-aqueous components.
  • it may be a solid-state electrode, for example any of those available commercially.
  • One form of these can be used to detect chloride ions (Cl ⁇ ) .
  • Examples of this type include ion-selective field effect transistors (conveniently referred to as "ISFET” devices) .
  • the detecting electrode e.g. ISE
  • ISE can be in any convenient shape. It is easy and convenient to make them in planar form, for example as a flat form of the coated wire.
  • the reference electrode can be another ISE which is under conditions which make it produce a stable EMF, in a manner comparable to a true conventional reference electrode.
  • This can, if desired, be another ISE with an inner (and constant) stable electrolyte within the porous liquid-junction membrane.
  • the permeable barrier surrounding the detecting electrode - or the detecting electrode and reference electrode - may be of various materials and forms. Its main function is to enclose the detecting electrode (or the detecting electrode and reference electrode assembly) and providing the means for contact with the sample, but also it may serve to hold the two electrode systems together as a single assembly, and even provide some protection for them against damage from contact with other bodies. Also, it usually contains a zone of liquid (e.g. electrolyte) medium enclosed within the permeable barrier. As the main function of the permeable barrier is to slow the rate of diffusion of analyte, it is preferably is not selective in favour of the analyte sought .
  • the permeable barrier may be made of any material which can provide the desired degree of permeability towards the sample or its components in addition to a sufficient degree of cohesion, strength and durability to maintain its physical integrity while the device is in contact with the sample and in use .
  • the detecting electrode e.g. ise
  • the reference electrode may produce a potential of its own (e.g. a "membrane potential") because such a potential, if generated, does not alter the potential difference which we wish to use -- i.e. the potential between the detecting electrode and the reference electrode .
  • the diffusion is a function of the concentrations of the species (e.g. ion species) on opposite sides of the permeable barrier, and in its simplest form that is all that is required of it, as it then functions only to regulate the access of the sample or its components to the detecting electrode. This regulation can be very helpful in keeping the concentration of the components affecting the detecting electrode potential within limits which allow ease of measurement or preventing excessive amounts contacting the detecting electrode and distorting the output signal or potential from it and consequently distorting the accuracy of measuremen .
  • the diffusion is usually inward diffusion (i.e. through the permeable barrier from the sample towards the detecting electrode) by the analyte species (e.g. ionic species) to be determined.
  • the detecting electrode being uniformly exposed to the inwardly diffusing species to be measured. It also has the advantage that the detecting electrode is less likely to be exposed to any unsuitably high concentration of the analyte species before the measurement is completed - as could be the case if the sample contains a very high ionic concentration and an ISE or redox electrode, as detecting electrode, were exposed directly to the sample.
  • the measurement usually can have been completed. Furthermore, it causes the concentration of the analyte in contact with the detecting electrode to change progressively as diffusion proceeds, and this change - especially the rate of change of concentration - is an exceptionally useful basis for the determination of analyte (e.g. ion) content which we wish to make and a key advantage provided in our present invention.
  • the contents of the permeable barrier may be provided with a concentration of the analyte species (the analyte ion when the detector electrode is an ISE) which is higher than that in the sample to be examined, so that diffusion of the analyte species will then be outwards - away from the detecting electrode and into the sample - so resulting in a decrease of its concentration adjacent to the detecting electrode.
  • This mode can also be used, as it is the rate of change that can be more important for the measurement purposes than the the absolute concentration itself or whether it is increasing or decreasing - especially when using an ISE.
  • the permeable barrier may have selective properties, especially in the way it limits diffusion.
  • This limitation of diffusion is distinct from selectivity on the basis of other phenomena.
  • This limitation of diffusion is distinct from an ISE membrane selectivity phenomenon. This could be important in improving the apparent selectivity of a detecting electrode, especially a redox electrode, and improved usefulness of our invention may be secured by making the barrier of a material which provides some degree of selectivity. This may then enable the device to exclude any components which could compromise the selective functioning of the detecting electrode, and so serve as a means for eliminating problematic interference with measurements being made.
  • a complete or high degree of selectivity may not be necessary, and even a partial discrimination against access by particular components may be sufficient to ensure satisfactorily reliable measurements - depending upon the particular application of the invention and the nature of the sample and/or the components sought to be determined.
  • a zone of liquid e.g. an electrolyte medium
  • some forms of detecting electrode may be able to function without the need for any such filling electrolyte,
  • This electrolyte medium may be provided in a variety of ways .
  • the device may be provided in the device as made. This allows the device to be made in a form suitable for sale or storage but also for immediate use.
  • the electrolyte can be in the form of a hydrated gel, which is both practicable and convenient .
  • the detecting electrode e.g. an ISE or redox electrode
  • a suitable liquid e.g. electrolyte solution
  • a thin permeable membrane e.g. a dialysis membrane
  • Such a membrane may comprise any conventional material, e.g. cellulose or cellulosic material as often used for dialysis membranes.
  • the robustness of the construction or the degree of permeability can be obtained by using multiple layers of the membrane (which may be the same or different) .
  • Using four layers of dialysis membrane can provide a very convenient form of such a device - though four is a number found to be convenient, and not an obligatory one.
  • the permeable barrier is adapted to interface with a sample under examination by the fact that at least the detecting electrode - and preferably both the detecting electrode and the reference electrode assembly - are enclosed within the permeable barrier. This enables all that is required of a sensor device to be included in a single unit, by carrying the detecting electrode and the reference electrode assembly upon a support which serves to hold the assembly together while insulating the detecting electrode and the reference electrode assembly from each other.
  • Various forms of construction may employed. For example, if the detecting electrode and the reference electrode assembly are assembled upon a substantially flat insulating support, the permeable barrier may take the form of a "bubble" or "envelope" over them.
  • the electrical connecting leads to the electrodes will need to be properly insulated, both chemically and electrically, from the media around them so as to avoid any interference of loss of the electrode signals.
  • the electrical connections to the two electrodes can be made in the usual manner and all the leads and connections from them insulated and sealed to pass through the region within the permeable barrier.
  • the measuring circuit may be any of the conventional ones for electrochemical measurement, and use conventional apparatus (meters, recording devices, and the like) for detecting an EMF or potential differences, and the signals from the electrode system of our devices can be interpreted and converted to specific measurements of components by conventional methods .
  • the detecting electrode is an ISE or redox electrode, it may suffer interference from unknown amounts of another species, e.g. ions or molecules. This interference can be reduced or eliminated by filling the enclosed region (around the detecting electrode and within the permeable barrier) with a zone of liquid (e.g.
  • an electrolyte containing an appropriately high concentration of this other species (especially an ion species) liable to interfere with the desired measurements, so that it can diffuse out through the permeable barrier and thereby reduce interference from that species if present in the sample.
  • concentration of the interfering species can near the detecting electrode can be kept substantially constant and its potentially troublesome effects can be reduced - and especially it can be kept effectively constant with time - so that measurements showing the rate of change of potential in the output signal due to the desired analyte can thus be distinguishable and used as the basis for determination of analyte content .
  • the components of a sample which can be determined by the use of an ISE according to the present invention are those for which the conventional ion-selective electrodes are applicable. These include anions, e.g. sodium (Na + ) and potassium (K + ) , and anions, e.g. nitrate (N0 3 ⁇ ) and fluoride (F " ) and chloride Cl " , but others may be determined if desired by appropriate ion-selective electrodes. Selectivity can sometimes be improved by appropriate choice of the barrier membrane. For example, selectivity for organic anions (e.g. chloride Cl " ) may be enhanced by use of an anionic barrier membrane.
  • the sample may be obtained and prepared in any conventional manner, but is preferably a liquid. If solids or samples which are not completely liquid are to examined, it may be necessary to add water or other aqueous solvent media to them to ensure that the components in them are put into a suitable state for measurement .
  • the analyte e.g. ionic analyte
  • the analyte may be present initially in the sample under examination as such (and therefore can be determined directly) , but if desired it may be generated in situ, for example by enzyme or chemical action (e.g. titration) and this may enable measurements of some analytes to be made indirectly.
  • indirect measurement can be useful as means for making one analyte into another which diffuses more readily through the permeable barrier or be detected at the detecting electrode
  • Redox measurements can also be made both directly and indirectly, and may be made in these ways using our invention. Examples of the latter are the "quinhydrone" sensors for ph and potentiometric titration systems, and other arrangements are possible. reagents or enzymes may be added to the sample in any form or immobilised or retailed above the covering permeable barrier (membrane) in liquid or dry form, or dried in a gel or liquid layer below it, for reaction above or below the permeable barrier (membrane) .
  • the sensor devices of this invention may be used in substantially the same way as an ordinary detecting electrode, by contacting the permeable barrier over the detecting electrode with the sample (if, necessary, prepared for this in the manner described above) . This may be done by applying it to the sensor device or, more conveniently, by dipping the sensor device into the sample. Of course, some forms of construction may be better adapted for particular modes of contacting with the sample, but the choice can easily be made to suit the particular situation and the user's preferences.
  • advantages which can be secured by use of an ISE or redox electrode in the sensor devices of the present invention include : - (1) the ISE (or redox electrode) and the reference electrode, being combined, make the device very much more easy and convenient to use.
  • the device is simple enough to be made disposable, for a "use once, no rinsing" procedure.
  • the device in its flat form, is of a very similar format to amperometric planar sensors, i.e. they can use different circuitry but the same fabrication and user presentation techniques, and so can offer opportunities for "mixed technique" multi-analyte sensor strips . (9) adaptable to use any ISE system.
  • devices of the invention include medical and clinical use, especially as a disposable sensor - which reduces risk of cross- contamination between sample or subjects; checks on levels of fertiliser components in soils, rivers, plant materials and the like; checks on levels of components (which may be considered to be desirable ones or may be any considered as contaminants or undesirable) in foods, waters, industrial liquid and effluents and the like. This is especially useful for the determination of ionic components or contaminants, by use of an ISE.
  • the device is most advantageous for single use in a constant sample, and after that use can be discarded. After making a single measurement, i.e. not continuous monitoring, the device can be "reconditioned" to some extent so that it can be used again, but this can be slow and not worthwhile. If it is to be re-used, the advantage of calibration avoidance is effectively lost .
  • the devices of our invention may be made in a variety of forms and shapes, to suit the particular needs of a user.
  • the device may be a single one - which can then be made conveniently small and inexpensively, and be most simple to use.
  • Other forms include combinations or arrays containing more than one of our sensor devices, which may be constructed to obtain an enhanced output signal for easier measurement or for special uses.
  • a form of interesting applicability is that in which several individual sensor devices of our invention are mounted together and the internal zone of liquid (e.g. electrolyte) of each of these, within the permeable barrier, is pre-loaded with different concentrations of the analyte to be sought and measured.
  • the flux of any interfering species ions or molecules, or the like
  • the fluxes of the desired analyte will be different and their differential behaviour will then be a function of the concentration of the desired analyte in the sample - and so enable interference effects to be reduced or eliminated.
  • Another variant of this is an array of a number of our sensor devices, each with its own internal electrolyte loaded with different pre-determined (and known) concentrations of the analyte sought .
  • the different sensors When such an array is contacted with the sample, the different sensors will give different responses - but for the particular sensor in which the loaded concentration of analyte (e.g. analyte ion) equals that in the sample there will be no diffusion through the permeable barrier and no potential change with time will be observed.
  • concentration of analyte e.g. analyte ion
  • This can reduce the need for detailed measurements to be made, as the sensor showing "no change" (“nil diffusion”) can be distinguished easily and quickly and will indicate the analyte concentration immediately.
  • a measurement may be made by using signals of more than one sensor element with appropriate signal processing methods.
  • An especial feature in using our invention is in the way in which the measurements are made and interpreted.
  • an ion to be determined diffuses through the permeable barrier and this progressive diffusion gives a continually changing response from the ISE/reference electrode combination.
  • the rate of change of response is most useful as an indication of the analyte content, and that it is possible to obtain more reliable measures of the analyte concentration by determining this .
  • measurements (by observation and recording) of the output potential of the electrode system are made, for example by being plotted, these show the rate of change of potential and can be used as an indication or measure of the analyte content .
  • the slope of the output is independent if any baseline EMF and also of the particular reference electrode used.
  • the responses are usually and conveniently measured in mV/minute, and are plotted as the rate of change of potential against the concentration or, preferably, against the log concentration.
  • the absolute value of the ISE/reference or redox/reference potential is not important so long as the reference keeps stable during the short time required for measurement, the problems previously caused by long term drift are minimised, and the need for calibrations for use are rendered substantially unnecessary.
  • the baseline EMF of ISE systems may drift about, this slope of the response plot is much more stable. This is in contrast to the usual way in which an ISE is used, which involves waiting long enough for the ISE to be at equilibrium. Similar effects are seen with redox systems .
  • the principle of operation of the invention lies in the use of an enclosing permeable barrier to provide a zone of liquid (usually an electrolyte) in contact with the detecting electrode - and possibly with both the detecting electrode and reference electrode - so that this zone of liquid acts as an intermediate phase which can act to moderate the extreme conditions which may which may be present in a sample under examination.
  • the membrane regulates the passage of components (e.g. ions) - whether analyte components or not - between the sample and the zone adjacent to the detecting electrode, in either direction. This serves to improve the ability of the electrode system (detector electrode and reference electrode) to cope with a wider variety of samples and give greater ease and accuracy of measurement than is practicable when the electrode system is exposed directly to the sample under examination. More particularly, it enables rate measurements to be made as detected species cross the permeable barrier (membrane) and alter the concentration in the inner liquid region.
  • FIGS 1 and 2 represent illustrations of forms of sensor constructed according to the present invention, and are schematic drawings, in transverse section and not to scale.
  • a planar sheet of ceramic material of approximately 0.5 mm thickness and 1.5 cm by 3.0 cm in area (1) serves as an insulating support and carries, upon one of its planar surfaces, two electrodes -- (A) an ion- selective electrode comprising a thick metallic film (2) of platinum deposited from a platinum-containing ink or paint and coated with an ion-selective material (3) , and (B) a standard reference electrode (4) comprising a film of silver coated with silver chloride, surrounded by an aqueous solution (5) of potassium chloride (concentration in the range 0.5 to 3.5 M) (5) and enclosed within a porous layer (6) to serve as the required liquid junction in use.
  • A an ion- selective electrode comprising a thick metallic film (2) of platinum deposited from a platinum-containing ink or paint and coated with an ion-selective material (3)
  • B a standard reference electrode (4) comprising a film of silver coated with silver chloride, surrounded by an aqueous solution (5) of potassium chloride
  • the two electrodes (A) and (B) are totally enclosed by a permeable barrier layer or membrane (8) which also makes sealing contact with the sheet of insulating support material (1) all around the area containing both electrodes.
  • a permeable barrier layer or membrane (8) which also makes sealing contact with the sheet of insulating support material (1) all around the area containing both electrodes.
  • the space between this enclosing membrane (8) and the two electrodes (A) and (B) is filled with an aqueous solution (7) of sodium chloride. This completes the electrolyte-filled permeable barrier as the enclosure for the pair of electrodes.
  • electrical leads are fitted (10 and 11 respectively) to provide electrical connection to the electrodes (A) and (B) (more specifically, to the conducting films (2) and (4) .
  • These leads (10 and 11) are sealed into the sheet (l) to prevent leakage of liquid past them, and are insulated and provided with means for connection to a voltage measuring device V (not shown) .
  • a liquid sample to be examined (9) is put into contact with the surrounding membrane (8) .
  • this is done by simple dipping the assembly (constructed as described above) into the sample liquid (9) .
  • the insulation covering on the connecting leads (10 and 11) ensures that there is no electrical short-circuit occurring between them.
  • the assembly is laid horizontally, with the electrodes, membranes, etc. uppermost, and the sample is then applied on top of the outer membrane (8) .
  • This construction allows electrolyte contact at each of the membranes (3) and (8) and also the bridging part (7) , to allow the completion of an electrically conducting circuit between electrode (A) and (B) , which avoids direct exposure of electrode coverings (3 ( and (6) to the sample (9) itself.
  • Measurement of the potential between the two electrodes (A) and (B) is made by an appropriate meter, usually an ISE meter, typically a voltmeter with a single high impedance input for the ISE.
  • Figure 2 which represents a transverse section of part of a long strip of a ceramic base (1) coated with a pair of metallic stripes (12) and (13) .
  • Stripe (12) is of gold and serves as a conductor for the ISE part
  • stripe (3) is of metallic silver coated with silver chloride and serves as the reference electrode.
  • Over the base (11) is a layer of insulating material (14) , made by casting a solution of un-plasticised PVC in tetrahydrofuran over the stripe-coated ceramic base and allowing the solvent to evaporate off .
  • PVC (14) and completely covers the electrodes. Electrical connections are made (by means not shown, but conveniently comprising the ends of stripes (12) and (13) protruding from under the PVC layer (14) beyond the "well” or “window” filled by the layers (15) and (16) .
  • the sample is then contacted with the of the polyvinyl alcohol layer (16) , and the potential difference between electrodes (12) and (13) is measured.
  • the un-plasticised PVC used has a molecular weight of 100,000 to 200,000 and is dissolved in tetrahydrofuran. This is used to form the PVC layers.
  • the solution of un-plasticised PVC in tetrahydrofuran is used, with addition of tri-caprylyl methyl ammonium chloride as plasticiser and as ion carrier for chloride or with di- octyl phthalate as plasticiser and valinomycin as ion- carrier for potassium.
  • the layers of metal are deposited from metal- containing paints, in conventional manner, and the various coatings of polymer-based material are applied by dip- coating the ceramic strip in the solutions, masking areas which are not to be coated and cutting out parts of the applied coatings where a "well” or “window” is to be formed.

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  • Investigating Or Analysing Biological Materials (AREA)

Abstract

L'invention porte sur des systèmes et dispositifs de détection comportant une électrode de détection (en particulier sélectrice d'ions ou redox) et une électrode de référence l'une ou toutes deux étant recouvertes d'une barrière perméable touchant l'échantillon à examiner de manière à ce que le principal contact entre les électrodes lorsqu'on constitue un circuit de mesure ne passe pas par l'échantillon. La barrière perméable renferme une zone de liquide (par exemple d'électrolyte) au niveau des électrodes et commande en le restreignant le passage dans les deux sens des analytes et impuretés à travers la barrière. La fonction principale de la barrière perméable est de ralentir la diffusion de l'analyte. L'identification du contenu d'analyte peut être plus rapide si l'on charge la zone liquide en analyte ou impureté pour réguler la diffusion. La méthode de loin préférée de détection de l'analyte se base sur des mesures du taux de variation du potentiel alors que l'analyte diffuse à travers la barrière.
EP98959014A 1997-12-11 1998-12-08 Dispositifs de detection et procede d'analyse Withdrawn EP1038172A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GB9726230 1997-12-11
GB9726230A GB2332278A (en) 1997-12-11 1997-12-11 Electrochemical sensor
GB9816909 1998-08-05
GBGB9816909.7A GB9816909D0 (en) 1998-08-05 1998-08-05 Sensor devices and analytical method
PCT/GB1998/003662 WO1999030144A1 (fr) 1997-12-11 1998-12-08 Dispositifs de detection et procede d'analyse

Publications (1)

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EP1038172A1 true EP1038172A1 (fr) 2000-09-27

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EP98959014A Withdrawn EP1038172A1 (fr) 1997-12-11 1998-12-08 Dispositifs de detection et procede d'analyse

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EP (1) EP1038172A1 (fr)
AU (1) AU1495299A (fr)
CA (1) CA2313795A1 (fr)
WO (1) WO1999030144A1 (fr)

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US8181531B2 (en) 2008-06-27 2012-05-22 Edwin Carlen Accessible stress-based electrostatic monitoring of chemical reactions and binding
US9011670B2 (en) 2008-08-14 2015-04-21 The Charles Stark Draper Laboratory, Inc. Three-dimensional metal ion sensor arrays on printed circuit boards
CN110337586B (zh) * 2017-02-22 2023-03-10 豪夫迈·罗氏有限公司 用于检测至少一种流体样品中的至少一种分析物的分析物检测器
CN108195900B (zh) * 2017-12-18 2024-01-05 江苏鱼跃凯立特生物科技有限公司 具有温度补偿的红细胞压积测试功能的电化学传感器

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AU1495299A (en) 1999-06-28
CA2313795A1 (fr) 1999-06-17

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