WO2023227432A1 - Électrode combinée avec diaphragme à hydrogel réticulé, et son procédé de production - Google Patents

Électrode combinée avec diaphragme à hydrogel réticulé, et son procédé de production Download PDF

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Publication number
WO2023227432A1
WO2023227432A1 PCT/EP2023/063214 EP2023063214W WO2023227432A1 WO 2023227432 A1 WO2023227432 A1 WO 2023227432A1 EP 2023063214 W EP2023063214 W EP 2023063214W WO 2023227432 A1 WO2023227432 A1 WO 2023227432A1
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WIPO (PCT)
Prior art keywords
hydrogel
diaphragm
support element
electrically conductive
inner tube
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PCT/EP2023/063214
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German (de)
English (en)
Inventor
Theo Gaupp
Dario BLUMENTHAL
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Hamilton Bonaduz Ag
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Publication of WO2023227432A1 publication Critical patent/WO2023227432A1/fr

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    • 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
    • G01N27/28—Electrolytic cell components
    • G01N27/401—Salt-bridge leaks; Liquid junctions
    • 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
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/36—Glass electrodes
    • 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
    • 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
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/301—Reference electrodes

Definitions

  • Combination electrode with a diaphragm comprising cross-linked hydrogel and method for producing the combination electrode
  • the invention relates to a combination electrode with a diaphragm that has a cross-linked hydrogel and is mechanically stabilized by a first support element and to a method for producing the combination electrode.
  • a combination electrode is a combination of a working electrode and a reference electrode housed in a single rod.
  • the term measuring electrode is also used synonymously for the term working electrode and the term reference electrode is also used synonymously for the term reference electrode.
  • the combination electrode can be, for example, a redox sensor or a pH combination electrode, by means of which a pH value can be determined.
  • the pH combination electrode can be, for example, a pH glass electrode.
  • the reference electrode is often a metal wire dipped in a saline solution.
  • the reference electrode is often a silver-silver chloride electrode, which has a silver wire covered by an AgCl layer, the silver wire with the AgCl layer being immersed in a KCl solution.
  • the KCI solution is limited by a diaphragm. In a single-rod measuring chain operation, the diaphragm is contacted with a measuring fluid to be examined.
  • the term working fluid is also used synonymously for the term measuring fluid.
  • the diaphragm is characterized by the fact that it prevents mixing of the KCl solution and the measuring fluid, but enables charge transport between the KCl solution and the measuring fluid.
  • Diaphragms with a porous structure are often used for this purpose; However, the resulting large surface area of the diaphragm is susceptible to contamination, which can make charge transport more difficult and thus lead to incorrect measurements.
  • KCl can flow from the combination electrode, with changes in the KCl concentration and thus the electrochemical potential Reference electrode can also cause incorrect measurements.
  • the KCl outflow and the degree of contamination can be significantly limited (DE 10 2018 132 108 A1).
  • Corresponding combination electrodes have a higher measurement accuracy and a longer service life.
  • the combination electrodes must often be sterilized, e.g. by autoclaving. Under conditions in autoclaves (high temperatures of around 120°C and a high pressure of around 2 bar), the hydrogel tends to swell, which affects the service life of a corresponding combination electrode.
  • a plug used in the publication DE 10 2018 132 108 A1 cited above proved to be insufficient to provide a mechanical barrier for the hydrogel.
  • the task is to increase the stability of a diaphragm containing hydrogel.
  • a first aspect of the invention relates to a combination electrode for measuring a working fluid, with a reference electrode arranged in a first volume having a first electrically conductive fluid and a working electrode arranged in a second volume having a second electrically conductive fluid, in which the first volume is at least one a cross-linked hydrogel diaphragm is limited, and wherein at least one first support element permeable to the working fluid is arranged on the side of the diaphragm facing away from the first volume.
  • a cross-linked hydrogel has significantly higher structural stability at elevated temperatures than a conventional, non-cross-linked hydrogel. It is advantageously stable at temperatures up to 140°C.
  • the cross-linked hydrogel is melt-resistant at the temperatures prevailing during autoclaving.
  • a corresponding diaphragm is therefore more suitable for sterilization by autoclaving than a conventional hydrogel and thus gives a corresponding combination electrode a longer service life.
  • a first support element gives the diaphragm additional stability against the pressure prevailing during autoclaving.
  • the first support element which can also be referred to as the first holding element, is permeable to the working fluid.
  • the permeability of the support element is prevented when the support element is pressurized. In other words, the support element then closes the fluid connection and prevents the cross-linked hydrogel of the diaphragm from being pressed outwards.
  • the first support element acts as a mechanical barrier for the hydrogel.
  • the first support element itself is mechanically stabilized by an internal projection of the material of the combination electrode, or by a step in the material of the combination electrode, or by a tension, for example if the first support element is designed as a spring ring.
  • the spring ring can be tensioned inwards or outwards.
  • the first support element is particularly advantageously arranged directly on the diaphragm.
  • the permeability of the first support element for the working fluid ensures charge transport from the working fluid to the hydrogel and further to the first electrically conductive fluid.
  • the permeability can be controlled by properties of a material of the first support element itself, for example by porosity, or by arranging, for example, through holes or grooves.
  • the cross-linking of the hydrogel and the mechanical barrier through the first support element have a synergistic effect by preventing the hydrogel from swelling out and thus destroying the diaphragm counteracted by temperature and pressure and thus increase the stability of the diaphragm and thus the service life of the combination electrode.
  • Ring-shaped designs of the first support element are particularly suitable because they can advantageously close tightly around the usually round component of a combination electrode, around which the diaphragm is also arranged.
  • the first support element is therefore preferably an annular element. It is possible, for example, to design the first support element as a spring ring or a snap ring. Preferably, the first support element is a spring ring. Also suitable is a ring that is only attached on one side (for example by gluing or tensioning) and has enough space on the other side for liquid to get past it.
  • the term “ring-shaped” as used here refers not only to closed rings, but also to three-quarter rings and similar designs.
  • Shapes other than ring-shaped designs are also possible.
  • the first support element may comprise spring steel, stainless steel or polymers such as polyetheretherketone (PEEK), polysulfone (PSU), polyphenylene sulfone (PPSU) or glass fiber reinforced polymers, e.g. glass fiber reinforced polyamides.
  • PEEK polyetheretherketone
  • PSU polysulfone
  • PPSU polyphenylene sulfone
  • glass fiber reinforced polymers e.g. glass fiber reinforced polyamides.
  • the first support element can also have sintered material.
  • the first support element can have through openings such as through holes or grooves.
  • the through openings advantageously allow liquid to pass through and close under high pressure.
  • the first support element preferably has a meandering structure.
  • Meandering here means that at least part of the material is designed as a strand and is arranged with constant and uniform changes of direction, but overall closed and ring-shaped, so that individual sections of the strand are arranged parallel to one another.
  • the meandering structure is particularly suitable for spring washers and advantageously enables the surface to be enlarged and therefore better Pressure distribution in the spring ring compared to rings made of the same material without a meandering structure.
  • the gaps between the parallel strands can be called microslots or macroslots depending on their size. The width of the gaps can be between 40 and 500 pm.
  • the gaps between the parallel strands can also be called slits.
  • the first support element preferably has recesses in the material.
  • the recesses can be arranged in the area of the inner edge of the first support element.
  • the first support element can also have depressions in the surface. The recesses and depressions also advantageously enable an increase in the surface area and thus a better pressure distribution in the first support element, for example the spring ring, compared to support elements made of the same material.
  • the first support element is formed in one piece.
  • the first support element consists in particular of a material. In particular, it only has one material from which it is provided in one piece.
  • At least one second support element that is permeable to the working fluid is arranged on the side of the first support element facing away from the diaphragm.
  • the second support element which can also be referred to as a second holding element, additionally stabilizes the first support element, so that the stability of the diaphragm is advantageously ensured even at high pressures.
  • the second support element preferably has the function of a valve that closes under pressure.
  • the second support element is preferably an annular element, more preferably an O-ring.
  • the O-ring in particular has an elastic material, so that the O-ring can be stretched like a rubber around or against the material of the combination electrode.
  • the elastic material is preferably a low-reaction polymer.
  • the second support element is permeable to the working fluid.
  • the permeability can be controlled by properties of a material of the second support element itself, for example by porosity, or by arranging, for example, through holes or recesses.
  • the second support element can be designed such that liquid passes the sides of the second support element. When pressure is applied, the diaphragm and the first support element press on the second support element, whose permeability is then prevented as with the first support element.
  • the hydrogel is preferably crosslinked by exposure to radiation.
  • the hydrogel is particularly preferably crosslinked by the action of beta radiation.
  • Beta radiation or ß radiation is ionizing radiation that occurs during radioactive decay, beta decay or beta transition.
  • the atomic nucleus of a beta emitter transforms into an atomic nucleus of another chemical element.
  • cross linking results in direct cross-linking of the polymer strands as well as breaks in the polymer strands and attachment of the corresponding bridge pieces to one another, so that cross-linking of the polymer strands occurs.
  • the hydrogel preferably has a degree of crosslinking in the range from 20 to 100%, more preferably from 35 to 90% and particularly preferably from 50 to 80%. If the degree of crosslinking is less than 20%, the desired melt resistance of the hydrogel may be too low at the temperatures prevailing during autoclaving. If the degree of crosslinking is too high, the hydrogel can become brittle, which can result in the desired sealing of the first volume through the diaphragm being lost.
  • the degree of networking can be controlled by the amount of energy entered.
  • the hydrogel particularly preferably has a degree of crosslinking of 60 to 70%. The degree of crosslinking of the hydrogel can be determined by determining the gel content.
  • the hydrogel is particularly preferably crosslinked by exposure to beta radiation with an absorbed dose of 100 kGy to 200 kGy, for example with an absorbed dose of 100 kGy, 150 kGy or 200 kGy. With these energy doses, a degree of crosslinking of the hydrogel in the range of 50 to 80% can be achieved if the hydrogel is irradiated in a dry state.
  • Beta radiation is particularly suitable for crosslinking the hydrogel because sufficient energy for crosslinking can be introduced into the hydrogel within a comparatively short period of time (a few seconds for up to 50 kGy compared to several hours under gamma radiation).
  • reactions are more likely to be initiated with the electrically charged particles (e.g. electrons in the case of beta-minus radiation), whereas gamma radiation is more likely to lead to oxidative degradation of the hydrogel due to the long period of irradiation required.
  • the hydrogel to be crosslinked heats up significantly less with beta radiation than with gamma radiation. Usually, several irradiations are carried out to enter a certain energy dose so that the hydrogel does not get too hot (e.g. for 100 kGy five irradiation units of 20 kGy).
  • the hydrogel preferably has a thermoplastic polyurethane.
  • the hydrogel essentially consists of the thermoplastic polyurethane.
  • the thermoplastic polyurethane is in particular a block copolymer containing a monomer A and a monomer B has:
  • the monomer is formed by the region that extends from the left bracket to the right bracket.
  • an oxygen atom can be attached to the left side of the monomer A or a hydroxyl group can be attached there to terminate the block copolymer.
  • a carbon atom can be attached to the right side of the monomer A or a hydrogen atom can be attached there to terminate the block copolymer.
  • An oxygen atom can be attached to the left side of the monomer B or a hydroxyl group can be attached there to terminate the block copolymer.
  • a carbon atom can be attached to the right side of the monomer B or a hydrogen atom can be attached there to terminate the block copolymer.
  • the block copolymer may consist essentially of blocks of monomer A and blocks of monomer B and end groups for terminating the block copolymer. The end groups can be the aforementioned hydroxyl groups and/or the aforementioned hydrogen atoms.
  • the mass ratio of monomer B to monomer A is from 20 to 100, in particular from 30 to 90.
  • the number-average molar mass M of the block copolymer is from 50*10 3 g/mol to 180*10 3 g/mol, in particular from 80*10 3 g/mol to 150*10 3 g/mol.
  • n is the number of polymer chains of the block copolymer and Mi is the molar mass of the polymer chain /.
  • the block copolymer is commercially available under the brand name Tecophilic® from Lubrizol. Examples of this are Tecophilic® TG-500 and/or Tecophilic® TG-2000.
  • the mass ratio of monomer B to monomer A is approximately 40 for Tecophilic® TG-500 and approximately 82 for Tecophilic® TG-2000.
  • the number-average molar mass M of the block copolymer for Tecophilic® TG-500 is approximately 1.4*10 5 g/mol and with Tecophilic® TG-2000 around 8*10 4 g/mol.
  • the block copolymer which is provided, for example, as granules, is dissolved in a solvent, poured into a mold and the solvent evaporates.
  • the solvent is preferably chloroform.
  • the hydrogel is irradiated after its production.
  • the hydrogel is advantageously irradiated in a swollen (wet) state. Irradiation of the hydrogel in the dry state is also possible, but is less effective compared to the swollen state and therefore results in a lower degree of crosslinking. On the other hand, irradiating the hydrogel when it is dry is easier to handle.
  • the hydrogel is preferably made from Tecophilic® TG-500 with chloroform as solvent and with a thickness of about 0.5 mm.
  • the hydrogel is then irradiated, preferably in a dry state, with beta radiation with an energy dose of 150 kGy for crosslinking.
  • the hydrogel may alternatively or additionally comprise another thermoplastic polymer.
  • the polymer must swell well in water so that it forms a hydrogel upon swelling.
  • the hydrogel may also include, for example, a polymer used in soft contact lenses. Examples of this include hydroxyethyl methacrylates, methyl methacrylates, vinylpyrrolidones and/or silicone hydrogels.
  • the hydrogel can be a thermoplastic elastomer.
  • the hydrogel can be a smart hydrogel. In particular the smart hydrogel can be ionic strength-responsive and/or thermoresponsive. An example of a smart hydrogel that is both ionic strength-responsive and thermoresponsive is the aforementioned Tecophilic®. Another example of a smart hydrogel that is thermoresponsive is a polymer based on N-isopropylacrylamide copolymers.
  • the hydrogel is a thermoplastic elastomer.
  • the thermoplastic elastomer can be extruded into a film and the diaphragm can then be punched out of the film.
  • the thermoplastic elastomer retains its elastic properties at room temperature.
  • An example of the thermoplastic elastomer is the block copolymer.
  • the hydrogel is a smart hydrogel, ie a stimuli-responsive hydrogel.
  • Smart hydrogels are characterized by the fact that they react to certain environmental conditions with pronounced volume changes. It is particularly advantageous that the smart hydrogel is ionic strength-responsive and/or thermoresponsive. In the case that the smart hydrogel is responsive to ionic strength, the lower the salt concentration or the conductivity of the working fluid, the more the smart hydrogel swells.
  • An example of such an ion strength-responsive smart hydrogel is the aforementioned block copolymer.
  • the low salt concentration in the working fluid means that more ions from the first electrically conductive fluid can diffuse into the working fluid via the now more swollen diaphragm, which causes a decreasing diffusion potential between the first electrically conductive fluid and the working fluid and thus a higher measurement accuracy.
  • the combination electrode with the ion strength-responsive smart hydrogel is therefore suitable for measuring ultrapure water.
  • the smart hydrogel is thermoresponsive, it can be designed to shrink with increasing temperature.
  • An example of such a thermoresponsive smart hydrogel is the aforementioned block copolymer.
  • the shrinkage of the smart hydrogel means that the smart hydrogel is less prone to contamination and reduces the outflow of ions from the first electrically conductive fluid, which means that the service life of the combination electrode is long even at elevated temperatures.
  • Another example of a smart hydrogel that is thermoresponsive is a polymer based on N-isopropylacrylamide copolymers.
  • the first volume a reference space formed between an outer tube and an inner tube, and the second volume, an inner tube space enveloped by the inner tube, and in which the inner tube has a first longitudinal end, which is designed to be closed, and a glass membrane which is electrically conductively connected to the working electrode arranged at a second longitudinal end of the inner tube by means of the second electrically conductive fluid, and in which the outer tube has a first longitudinal end on which the diaphragm is arranged, which is arranged by means of the first electrically conductive fluid is electrically conductively connected to the reference electrode arranged at a second longitudinal end of the outer tube.
  • the outer tube is synonymously referred to as the outer tube and the inner tube is synonymously referred to as the inner tube. This also applies to compound words.
  • the diaphragm thus seals an opening in the reference space in the direction of the working fluid, which is designed as an annular gap between the outer and inner tubes.
  • the opening can be sealed particularly tightly with the diaphragm by first introducing the hydrogel into the opening in its dry state. After contact with the first electrically conductive fluid, the hydrogel swells and thus seals the opening.
  • the hydrogel can be easily formed into a ring, for example by cutting and/or punching.
  • the first support element is preferably an element that at least partially encloses the inner tube. As a result, the first support element can stabilize the diaphragm, which seals the annular gap between the outer and inner tube, particularly well.
  • the first support element is particularly suitable because they can advantageously close tightly around the inner tube.
  • the first support element is a ring which is stretched around the inner tube.
  • the ring can be stretched outwards, i.e. against the outer tube.
  • the ring is preferably a spring ring.
  • the second support element is also preferably an element that at least partially encloses the inner tube.
  • the second support element can additionally stabilize the diaphragm and the first support element particularly well.
  • Annular designs of the second support element are particularly suitable because they can advantageously close tightly around the inner tube.
  • the second support element is a ring which is stretched around the inner tube.
  • the ring can, for example, have an elastic material and be stretched around the inner tube like a rubber.
  • the ring can be stretched outwards, i.e. against the outer tube.
  • the ring is preferably an O-ring.
  • the first longitudinal end of the outer tube preferably ends essentially flush with the first or second support element.
  • the combination electrode is preferably a pH combination electrode and/or a redox sensor.
  • the pH combination electrode is particularly preferably a pH glass electrode.
  • the first electrically conductive fluid can be an aqueous KCl solution, for example an aqueous 3 M KCl solution.
  • the first electrically conductive fluid can be a highly viscous liquid.
  • the aqueous KCl solution in particular the aqueous 3 M KCl solution, can be thickened with a thickener, in particular hydroxyethyl cellulose.
  • the Hydroxyethyl cellulose for example, can be purchased under the trade name Natrosol.
  • the first electrically conductive fluid can be highly solidified. To do this, a monomer mixture is introduced into the combination electrode and polymerized there to form a polymer.
  • the polymer can be, for example, a polymer that is obtained by polymerization of N-acryloylaminoethoxyethanol or by copolymerization of N-acryloylaminoethoxyethanol with a hydroxyalkyl methacrylate, as described, for example, in WO 2005/073704 A1.
  • the thickness of the diaphragm is preferably from 0.1 mm to 1.0 mm, in particular from 0.35 mm to 0.7 mm. It was found that with these thicknesses the outflow of KCl is low, but the charge exchange between the first electrically conductive fluid and the working fluid is so high that error-free measurements can be carried out with the combination electrode.
  • a second aspect of the invention relates to a method for producing a combination electrode, with the steps:
  • a first volume referred to as a reference space being formed between the outer tube and the inner tube and the outer tube and/or the inner tube delimiting an opening
  • the advantages of the method correspond to the advantages of the combination electrode according to the invention.
  • the opening can be sealed easily and particularly tightly using the method according to the invention.
  • the combination electrode produced by this process has a long service life compared to conventional combination electrodes whose diaphragm does not have a hydrogel, within which the combination electrode can carry out error-free measurements.
  • the combination electrode produced by the method is suitable for sterilization by autoclaving, in contrast to conventional combination electrodes, whose diaphragm does not have a cross-linked hydrogel and which does not have a first support element. This property gives the combination electrode an even longer service life.
  • the arrangement of the working electrode within the inner tube and the reference electrode within the outer tube can take place both before the introduction of the hydrogel and after the introduction of the hydrogel.
  • the cross-linked hydrogel is introduced into the opening in particular in a dry state.
  • the reference space of the fully assembled combination electrode can be filled in a vacuum from below, ie from the first longitudinal end of the outer tube.
  • the crosslinked hydrogel is also possible to introduce the crosslinked hydrogel into the opening in a swollen or slightly swollen state.
  • the reference space must then be filled from above, ie from the second longitudinal end of the outer tube, and only then can the combination electrode be fully assembled.
  • the cross-linked hydrogel is preferably treated with beta radiation before introduction.
  • a larger amount of the hydrogel can be irradiated in this way and then cut to size for introduction into individual diaphragms.
  • the method preferably includes irradiating the hydrogel with beta radiation at a certain energy dose.
  • a crosslinking accelerator is added to the hydrogel before treating it with beta radiation.
  • a crosslinking accelerator can be, for example, triallyl isocyanurate (TAIC).
  • TAIC triallyl isocyanurate
  • the crosslinking accelerator can, for example, be dissolved in a solvent together with a suitable polymer before the solution is poured into a mold and the solvent evaporates.
  • an annular element is provided as the first support element.
  • At least one second support element permeable to the working fluid is additionally arranged on the inner tube on the side of the diaphragm facing away from the first volume.
  • an annular element more preferably an O-ring, is provided as the second support element.
  • Figure 1 shows a schematic representation of a longitudinal section through a combination electrode according to an embodiment of the invention with a spring ring.
  • Figure 2 shows a detailed representation of a spring ring
  • Figure 3 shows a detailed representation of a spring ring with a partially meandering structure.
  • Figure 4 shows a section of the combination electrode according to Figure 1 according to a further embodiment of the invention with a spring ring and an O-ring.
  • Figure 5 shows a flow diagram of an embodiment of the method according to the invention.
  • a combination electrode 1 as shown in FIG. 1 has a working electrode 2, a reference electrode 3, a diaphragm 10 and a first electrically conductive fluid 6 for measuring a working fluid.
  • the first electrically conductive fluid 6 is in fluid contact with the reference electrode 3 and the diaphragm 10, so that the diaphragm 10 is electrically conductively connected to the reference electrode 3 via the first electrically conductive fluid 6.
  • the combination electrode 1 can be a pH combination electrode and/or a redox sensor.
  • the pH combination electrode can be a pH glass electrode.
  • the combination electrode 1 has an outer tube 4 and an inner tube 5 that is arranged within the outer tube 4.
  • the outer tube 4 is synonymously referred to here as the outer tube and the inner tube 5 is also synonymously referred to as the inner tube.
  • the volume between the two tubes is designed as a reference space 20 in which the first electrically conductive fluid 6 is arranged.
  • the outer tube 4 has a first outer longitudinal end 15 and a second outer longitudinal end 16. In the area of the first outer longitudinal end 15 a first inner tube longitudinal end 17 is arranged. In the area of the second outer tube longitudinal end 16, a second inner tube longitudinal end 18 is arranged.
  • An inner tube space 19 is formed in the inner tube 5, in which a second electrically conductive fluid 7 is arranged.
  • 1 has a storage vessel 8 at its first longitudinal end 17, the volume of which is fluidly connected to the inner tube space 19 and has a larger diameter than the inner tube 5, so that a larger amount of the second electrically conductive fluid 7 can be provided.
  • the combination measuring chain 1 has an opening in the reference space 20 in the form of an annular gap in the area of the first outer longitudinal end 15 and the first inner longitudinal end 17.
  • the diaphragm 10 is arranged in the opening and seals the opening.
  • the thickness of the diaphragm 10 is specified in relation to the extension between the first inner tube longitudinal end 17 to the second inner tube longitudinal end 18.
  • the thickness of the diaphragm 10 can be from 0.1 mm to 1.0 mm, in particular from 0.35 mm to 0.7 mm.
  • a liquid channel 11 can be provided from the diaphragm, which leads to the first outer longitudinal end 15 (FIG. 4).
  • the diaphragm 10 is characterized in that it prevents mixing of the first electrically conductive fluid 6 and the working fluid, but enables charge transport between the first electrically conductive fluid 6 and the working fluid.
  • the side of the diaphragm 10 facing away from the first electrically conductive fluid 6 must be contacted with the working fluid.
  • the combination electrode 1 has a glass membrane 9 in the area of the first inner tube longitudinal end 17.
  • the glass membrane 9 is electrically conductively connected to the working electrode 2 via the second electrically conductive fluid 7.
  • the first electrically conductive fluid 6 and the second electrically conductive fluid 7 are electrically insulated from each other.
  • the working fluid is also measured with the side of the glass membrane 9 facing away from the second electrically conductive fluid 7 contacted and an electrical voltage was measured between the working electrode 2 and the reference electrode 3.
  • the diaphragm 10 has a cross-linked hydrogel.
  • the diaphragm 10 can also consist essentially of the cross-linked hydrogel.
  • the hydrogel may comprise a thermoplastic polyurethane.
  • the thermoplastic polyurethane may be a block copolymer containing a monomer A The monomer is formed by the region that extends from the left bracket to the right bracket.
  • an oxygen atom can be attached to the left side of the monomer A or there can be an oxygen atom there to terminate the block copolymer Hydroxyl group be attached.
  • a carbon atom can be attached to the right side of the monomer A or a hydrogen atom can be attached there to terminate the block copolymer.
  • An oxygen atom can be attached to the left side of the monomer B or a hydroxyl group can be attached there to terminate the block copolymer.
  • a carbon atom can be attached to the right side of the monomer B or a hydrogen atom can be attached there to terminate the block copolymer.
  • the block copolymer may consist essentially of blocks of monomer A and blocks of monomer B and end groups for terminating the block copolymer.
  • the end groups can be the aforementioned hydroxyl groups and/or the aforementioned hydrogen atoms.
  • the mass ratio of monomer B to monomer A can be from 20 to 100, in particular from 30 to 90.
  • the number-average molar mass M of the block copolymer can be from 50*10 3 g/mol to 180*10 3 g/mol, in particular from 80*10 3 g/mol to 150*10 3 g/mol.
  • M where n is the number of polymer chains of the block copolymer and Mi is the molar mass of the polymer chain /.
  • the block copolymer is commercially available under the brand name Tecophilic® from Lubrizol. Examples of this are Tecophilic® TG-500 and/or Tecophilic® TG-2000.
  • the mass ratio of monomer B to monomer A is approximately 40 for Tecophilic® TG-500 and approximately 82 for Tecophilic® TG-2000.
  • the number-average molar mass M of the block copolymer for Tecophilic® TG-500 is approximately 1.4*10 5 g/mol and with Tecophilic® TG-2000 around 8*10 4 g/mol.
  • the hydrogel may also include, for example, a polymer used in soft contact lenses. Examples of this include hydroxyethyl methacrylates, vinylpyrrolidones and/or silicone hydrogels.
  • the hydrogel can be a thermoplastic elastomer.
  • the Hydrogel can be a smart hydrogel.
  • the smart hydrogel can be ionic strength-responsive and/or thermoresponsive. In the case that the smart hydrogel is thermoresponsive, it may be such that it swells and/or shrinks more at higher temperatures. There may be a transition temperature in which the hydrogel changes behavior between swelling and shrinking.
  • An example of a smart hydrogel that is both ionic strength-responsive and thermoresponsive is the aforementioned Tecophilic®.
  • Another example of a smart hydrogel that is thermoresponsive is a polymer based on N-isopropylacrylamide copolymers.
  • the polymers in the hydrogel are crosslinked by irradiation with ß-rays.
  • the degree of crosslinking of the hydrogel can be 20 to 100%, in particular 50 to 80% and more preferably 60 to 70%.
  • the cross-linked hydrogel has increased temperature resistance compared to conventional, non-cross-linked hydrogels.
  • the cross-linked hydrogel is stable at temperatures up to 140°C.
  • the hydrogel is made in particular from Tecophilic® TG-500 and has a thickness of approximately 0.5 mm.
  • the hydrogel was irradiated in a dry state with beta radiation with an absorbed dose of 150 kGy for crosslinking.
  • a spring ring 30 is arranged as the first support element in the area on the side of the diaphragm 10 facing away from the reference space 20.
  • a sintered ring can also be arranged.
  • the spring ring 30 is held mechanically by a step in the corresponding area of the first outer longitudinal end 15.
  • the material of the spring ring is spring steel, stainless steel or polymers such as polyether ether ketone (PEEK), polysulfone (PSU), polyphenylene sulfone (PPSU) or glass fiber reinforced polymers, for example glass fiber reinforced polyamides.
  • the spring ring 30 has an outer edge (outer edge) 31 and an inner edge (inner edge) 32. In the embodiment shown in FIG.
  • the spring ring 30 starts from the inner edge 32 recesses 34 are arranged in the form of bulges, which are also referred to as slots.
  • the slots can be chosen to be larger or smaller based on their size and distance from one another, and can then be referred to as macroslots (FIG. 2A) or microslots (FIG. 2B).
  • the slots can be formed in various shapes, for example, elongated (FIG. 2A) or rounded (FIG. 2B), but are not limited thereto.
  • the first outer tube longitudinal end 15 is arranged essentially flush with the spring ring 30.
  • the material of the spring ring 30 is designed in a meandering shape.
  • the material is arranged in strand form with constant changes of direction, so that a section of the material is arranged parallel to its adjacent sections connected to it, and overall forms a ring shape.
  • the spring ring is completely formed with a meandering structure 33.
  • the spring ring can also be only partially meander-shaped, for example in the area of the inner edge 32, and in the area of the outer edge 31 with a compact structure.
  • the combination electrode has an O-ring 40 as a second support element, which is arranged in the area on the side of the spring ring 30 facing away from the diaphragm 10.
  • the O-ring 40 has, in particular, an elastic material as a material.
  • the O-ring essentially consists of the elastic material. Examples of suitable elastic materials are natural or artificial elastomers, rubbers such as ethylene-propylene-diene rubber (EPDM) or fluoro rubber (FKM). or silicone.
  • EPDM ethylene-propylene-diene rubber
  • FKM fluoro rubber
  • silicone silicone.
  • the O-ring 40 is designed as a static spring which is arranged to stabilize the spring ring 30 and thus also to stabilize the hydrogel against increased pressure. As can be seen from FIG.
  • the combination electrode 1 can have a seal 21 which is inserted into the inner tube 5 and seals the inner tube space 19.
  • the second electrically conductive fluid 7 is thus arranged between the first inner tube longitudinal end 17 and the seal 21.
  • the seal 21 can be an adhesive, in particular a silicone adhesive.
  • the combination measuring chain 1 can have a seal 14, which is arranged in the annular gap between the outer tube 4 and the inner tube 5 in the area of a second outer tube longitudinal end 16, which is arranged facing away from the first outer tube longitudinal end 15, and seals the reference space 20.
  • the first electrically conductive fluid 6 is thus arranged between the diaphragm 10 and the seal 14.
  • the combination electrode 1 can have a head part 12 which encloses the outer tube 4 at its second longitudinal end 16.
  • the head part 12 protrudes from the second outer longitudinal end 16.
  • the head part 12 has a cavity in its interior which is filled with a casting compound 13.
  • the potting compound 13 can seal again in addition to the seal 14 and the seal 21.
  • the casting compound 13 can be a silicone adhesive.
  • an outer tube 4 and an inner tube 5 are provided in a first step S1, the inner tube 5 being arranged in the outer tube 4.
  • the first volume delimited by the tubes forms a reference space 20, which has an opening.
  • a second electrically conductive fluid 7 and a working electrode 2 are arranged in the second volume delimited by the inner tube, also referred to as the inner tube space 19.
  • a reference electrode 3 is arranged inside the outer tube 4 at the second outer tube longitudinal end 16.
  • a hydrogel treated by beta radiation and thereby crosslinked is introduced into the opening in a dry state.
  • the reference space 20 is delimited by the cross-linked hydrogel.
  • the irradiation of the hydrogel is carried out in a separate, dedicated facility in a manner that is clear to those skilled in the art.
  • the hydrogel is crosslinked by exposure to beta radiation with an energy dose of 100 kGy to 200 kGy.
  • a crosslinking accelerator is added to the hydrogel before irradiation with beta radiation.
  • Triallyl isocyanurate (TAIC) is used as a crosslinking accelerator.
  • TAIC is used in a concentration of 1 to 3% and allows the desired degree of cross-linking of the hydrogel to be achieved at lower energy doses.
  • the crosslinking accelerator is added to the hydrogel by dissolving the crosslinking accelerator together with the polymer of the hydrogel in a solvent before the solution is poured into a mold and the solvent evaporates.
  • the crosslinking accelerator can be added to the hydrogel after casting.
  • the hydrogel Before being introduced into the opening, the hydrogel is cut into an adequate shape adapted to the dimensions of the combination electrode 1.
  • the hydrogel can be smaller than the opening and after introducing the first electrically conductive fluid 6 into the reference space 20, the diaphragm 10 formed can be under a compressive stress.
  • the person skilled in the art can, in a preliminary test, contact hydrogels of different sizes, which are in their dry state and are smaller than the opening, with the first electrically conductive fluid 6 and allow them to swell.
  • the size of the hydrogels in their swollen state is determined and only those hydrogels of different sizes that are larger than the opening in their swollen state are suitable for the diaphragm 10.
  • Hydrogels of different sizes can be selected which, in their swollen state, are 10% to 100% larger than the opening, especially from 30% to 50% larger than the opening.
  • the degree of swelling Q of the hydrogel can be from 115% to 1000%, in particular from 150% to 800%, in particular from 180% to 350%.
  • a first electrically conductive fluid 6 is introduced into the reference space 20.
  • the hydrogel is contacted with the first electrically conductive fluid 6, causing it to swell and thus form a diaphragm 10 and seal the opening.
  • the reference electrode 3 is also contacted with the first electrically conductive fluid 6, so that the diaphragm 10 is electrically conductively connected to the reference electrode 3 via the first electrically conductive fluid 6.
  • the first outer longitudinal end 15 is immersed in the first electrically conductive fluid 6, the combination electrode 1 is introduced together with the first electrically conductive fluid 6 into a vacuum container, the vacuum container is evacuated and then ventilated , so that the first electrically conductive fluid 6 enters the reference space 20 via the opening.
  • the second outer tube longitudinal end 16 can be sealed by means of the sealing ring 14 and/or by means of the head part 12 and the casting compound 13.
  • the vacuum container can be evacuated up to a pressure of 50 mbar to 100 mbar, in particular 80 mbar.
  • a spring ring 30 is arranged as a first support element on the side of the diaphragm 10 facing away from the reference space 20 on the outside of the inner tube 5.
  • an O-ring 40 can be arranged as a second support element on the side of the spring ring 30 facing away from the diaphragm 10 on the outside of the inner tube 5.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
  • Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)

Abstract

L'invention concerne une électrode combinée (1) pour mesurer un fluide de travail, comprenant une électrode de travail (2), une électrode de référence (3), un diaphragme (10), et un premier fluide électroconducteur (6), qui est en contact avec l'électrode de référence (3) et le diaphragme (10) de telle sorte que le diaphragme (10) est connecté à l'électrode de référence (3) d'une manière électriquement conductrice par l'intermédiaire du premier fluide électroconducteur (6), le diaphragme (10) comportant un hydrogel réticulé et étant stabilisé par au moins un élément de support. L'invention concerne également un procédé de fabrication de l'électrode combinée (1).
PCT/EP2023/063214 2022-05-27 2023-05-17 Électrode combinée avec diaphragme à hydrogel réticulé, et son procédé de production WO2023227432A1 (fr)

Applications Claiming Priority (2)

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DE102022113419.9A DE102022113419A1 (de) 2022-05-27 2022-05-27 Einstabmesskette mit vernetztes Hydrogel aufweisendem Diaphragma und Verfahren zum Herstellen der Einstabmesskette
DE102022113419.9 2022-05-27

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WO2023227432A1 true WO2023227432A1 (fr) 2023-11-30

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498899A (en) * 1965-06-18 1970-03-03 Beckman Instruments Inc Electrochemical electrode assembly
WO2005073704A1 (fr) 2004-01-28 2005-08-11 Mettler-Toledo Gmbh Electrolyte polymere, demi-cellule pour mesures electrochimiques, et leur utilisation
DE102018132108A1 (de) 2018-12-13 2020-06-18 Hamilton Bonaduz Ag Einstabmesskette mit Hydrogel aufweisendem Diaphragma und Verfahren zum Herstellen der Einstabmesskette
EP3742158A1 (fr) * 2019-05-21 2020-11-25 ABB Schweiz AG Électrode de référence pour un capteur de ph et capteur de ph

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2908775B1 (fr) 2006-11-17 2012-08-31 Biomatlante Hydrogel et ses applications biomedicales

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498899A (en) * 1965-06-18 1970-03-03 Beckman Instruments Inc Electrochemical electrode assembly
WO2005073704A1 (fr) 2004-01-28 2005-08-11 Mettler-Toledo Gmbh Electrolyte polymere, demi-cellule pour mesures electrochimiques, et leur utilisation
DE102018132108A1 (de) 2018-12-13 2020-06-18 Hamilton Bonaduz Ag Einstabmesskette mit Hydrogel aufweisendem Diaphragma und Verfahren zum Herstellen der Einstabmesskette
EP3742158A1 (fr) * 2019-05-21 2020-11-25 ABB Schweiz AG Électrode de référence pour un capteur de ph et capteur de ph

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SETIAWAN L ET AL: "RADIATION-INDUCED MODIFICATION OF THERMOPLASTIC ELASTOMERS", INTERNATIONAL POLYMER SCIENCE AND TECHNOLOGY, RAPRA TECHNOLOGY, SHREWABURY, GB, vol. 22, no. 11, 1 November 1995 (1995-11-01), pages T/10 - T/17, XP000583779, ISSN: 0307-174X *

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