Heterogeneous membrane electrodes

• US 7,767,068 B2
• Filed: 06/01/2004
• Issued: 08/03/2010
• Est. Priority Date: 12/02/2002
• Status: Active Grant

• Current Assignee: Siemens Healthcare Diagnostics Incorporated (Siemens AG)
• Original Assignee: Epocal Incorporated (Siemens AG)
• Inventors: Bales, Michael, Oussova, Alexandra, Varlan, Anca, Lauks, Imants
• Primary Examiner(s): Michener; Jennifer K
• Assistant Examiner(s): Dam; Dustin Q
• Application Number:
  US10/856,929
• Publication Number:
  US 20040231984A1
• Time in Patent Office: 2,254 Days
• Field of Search: 204/416, 204/431
• US Class Current: 204/416
• CPC Class Codes: B01L 2200/025 Align devices or objects to ensure defined positions relative to each other
• CPC Class Codes: B01L 2200/148 Specific details about calibrations
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0825 Test strips
• CPC Class Codes: B01L 2300/0883 Serpentine channels
• CPC Class Codes: B01L 2300/0887 Laminated structure
• CPC Class Codes: B01L 2400/0487 fluid pressure, pneumatics
• CPC Class Codes: B01L 2400/0683 mechanically breaking a wall or membrane within a channel or chamber
• CPC Class Codes: B01L 3/5027 by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip B01L3/5023 takes precedence; micromixers B01F33/30; microreactors for synthesis B01J19/0093; microcapillary devices in general B81B1/00
• CPC Class Codes: B01L 3/502715 characterised by interfacing components, e.g. fluidic, electrical, optical or mechanical interfaces
• CPC Class Codes: G01N 27/301 Reference electrodes
• CPC Class Codes: G01N 27/307 Disposable laminated or multilayered electrodes G01N27/3272 takes precedence
• CPC Class Codes: G01N 27/31 Half-cells with permeable membranes, e.g. semi-porous or perm-selective membranes

Abstract

The present invention relates to planar electrochemical sensors with membrane coatings used to perform chemical analyses. The object of this invention is to provide unit-use disposable sensors of very simple and inexpensive construction, preferably with only a single membrane coating on an electrode. The invented devices are potentiometric salt-bridge reference electrodes and dissolved gas sensors constructed with a heterogeneous membrane coating of a conductor. The heterogeneous membrane, which is an intimate admixture of a hydrophobic and a hydrophilic compartment, concurrently supports constrained transport of non-volatile species through its hydrophilic compartment and rapid gas and water vapor transport through its hydrophobic compartment.

Claims

1. An electrode for use in an electrochemical sensing device for the analysis of an aqueous sample, comprising;

an insulating substrate layer having first and second sides, the insulating substrate layer having an opening defining an electrode region;

an electric conductor located on the first side of the insulating substrate layer and closing the aperture on the first side; and

a dry heterogeneous membrane for direct contact with the sample, the heterogeneous membrane being located on the second side of the insulating substrate layer and closing the aperture on the second side, the heterogeneous membrane being in electric contact with the conductor in the electrode region, the heterogeneous membrane including a hydrophobic compartment, a hydrophilic compartment and a dry internal reagent reservoir, the hydrophobic compartment being gas permeable and having a water vapor diffusion coefficient, the hydrophilic compartment being electrolyte salt permeable and having an aqueous electrolyte diffusion coefficient, wherein the hydrophobic compartment is in excess of the hydrophilic compartment for the water vapor diffusion coefficient of the hydrophobic compartment to be higher than the aqueous electrolyte diffusion coefficient of the ion conducting electrolyte compartment to maintain the electrode in a substantially dry, inactive condition at ambient conditions and to render the electrode convertible into a wet-up, active condition by water vapor penetration through the hydrophobic compartment into the internal reagent reservoir upon exposure of the heterogeneous membrane to an aqueous liquid.

2. The electrode as defined in claim 1, wherein the hydrophilic compartment incorporates the internal reagent reservoir.

3. The electrode as defined in claim 1, further comprising

a dry hydrophilic layer in electrical contact with the conductor in the electrode region, wherein the heterogeneous membrane is in physical contact with the insulating substrate layer at the electrode region and in electrical contact with the hydrophilic layer in the electrode region, at least one of the hydrophilic layer and the hydrophilic compartment of the heterogeneous membrane incorporating the internal reservoir.

4. The electrode as defined in claim 3, wherein the internal reservoir includes reagents and the membrane in the active condition, upon exposure to the aqueous sample fluid, permits diffusion of the reagents from the internal reservoir into the sample fluid.

5. The electrode as defined in claim 4, wherein the heterogeneous membrane in the active condition further permits diffusion of contaminants into the membrane layer.

6. The electrode as defined in claim 1 for use in a unit-use disposable salt-bridge reference electrode.

7. The electrode as defined in claim 1 for use in a unit-use disposable potentiometric gas sensor.

8. The electrode as defined in claim 1 for use as a unit-use disposable polarographic gas electrode.

9. The electrode as defined in claim 1, wherein the conductor is a gold layer.

10. The electrode as defined in claim 1, wherein the heterogeneous membrane is a layer cast from a liquid.

11. The electrode as defined in one of claim 1, wherein the heterogeneous membrane is cast from an oil in water emulsion.

12. The electrode as defined in claim 11, wherein the oil portion of the emulsion comprises a polymer or polymer precursor, or a mixture of polymers or polymer precursors, or derivatized polymers or polymer precursors selected from the following polymer families:

polysiloxanes, polyurethanes, polyphosphazenes, polybutadienes, polyisoprenes, epoxies and polyvinylacetates.

13. The electrode as defined in claim 11, wherein the water portion of the emulsion comprises a dissolved polymer or a polymer precursor, or a mixture of polymers or derivatized polymers selected from the following group of polymer families:

polyvinylalcohols, polyhydroxymethacrylates, polyacrylamides, polysaccharides, cellulosic polymers and gelatins.

14. The electrode as defined in claim 10, wherein the heterogeneous membrane is cast by a method selected from the group of printing by dispensing through a nozzle, pin-transfer printing, spin-coating, dip-coating, and screen-printing.

15. The electrode as defined in claim 1, wherein the hydrophobic compartment comprises a polymer or a derivatized polymer, or a mixture of polymers or derivatized polymers selected from the following group of polymer families:

polysiloxanes, polyurethanes, polyphosphazenes, polybutadienes, polyisoprenes, epoxies, polyvinylacetates and combinations thereof.

16. The electrode as defined in claim 1, wherein the hydrophilic compartment includes a hydrophilic polymer or a mixture of polymers including derivatized polymers selected from the following group of polymer families:

polyvinylalcohols, polyhydroxyacrylates, polyacrylamides, polysaccharides, cellulosic polymers and gelatins and combinations thereof.

17. The electrode of claim 1, for use in a sensing device constructed for sequential exposure of the electrode to an aqueous calibrator fluid and the sample fluid.

18. The electrode of claim 1, wherein the hydrophobic compartment includes a gas permeable polymer and the hydrophilic compartment includes a hydrophilic polymer, at least one of the hydrophobic polymer and the hydrophilic polymer being cross-linkable.

19. The electrode of claim 18, wherein the at least one polymer is at least partially cross-linked.

20. The electrode of claim 19, wherein the at least one polymer was cross-linked by a photo-initiated cross-linking process.

21. The electrode of claim 18, wherein the membrane is cast from a liquid and the cross-linking is performed after casting.

22. The electrode of claim 1, wherein the water vapor diffusion coefficient is at least 10 times larger than the salt aqueous electrolyte diffusion coefficient.

23. The electrode of claim 22, wherein the water vapor diffusion coefficient is at least 50 times larger than the aqueous electrolyte diffusion coefficient.

24. The electrode of claim 1, wherein the water vapor diffusion coefficient is greater than 1×

10<sup>−

6</sup> cm²s<sup>−

1</sup> and the aqueous electrolyte diffusion coefficient is less than 1×

10<sup>−

7</sup> cm²s<sup>−

1</sup>.

25. The electrode of claim 1, wherein the hydrophilic compartment is less than 5% by volume of the total volume of the heterogeneous membrane.

26. The electrode of claim 1, wherein the electric conductor is a metal foil and the insulator is a foil laminated thereto.

27. The electrode as defined in claim 2 for use as a potentiometric reference electrode, wherein the internal reservoir also includes a redox salt for electrochemical reaction at the electric conductor.

28. The electrode as defined in claim 27 for use as a potentiometric reference electrode, wherein the hydrophilic compartment comprises a salt composition which is approximately equi-transferrent.

29. The electrode as defined in claim 27, wherein the redox salt is selected from the group of ferrocyanide, ferricyanide, Prussian blue and combinations thereof.

30. The electrode as defined in claim 1 for use as a potentiometric reference electrode, wherein the heterogeneous membrane comprises a hydrophobic compartment containing acrylated siloxane and a hydrophilic compartment containing polyvinylalcohol.

31. The electrode of claim 1 for use as a polarographic oxygen electrode, wherein the heterogeneous membrane has an oxygen permeability of less than 6×

10<sup>−

13</sup> mole cm<sup>−

1</sup>s<sup>−

1</sup>atm<sup>−

1</sup>.

32. The electrode of claim 1 for use as a polarographic oxygen electrode wherein the hydrophobic compartment contains a compound selected from the group of acrylated epoxy, acrylated urethane, blends thereof and copolymers of at least one of acrylated epoxy and acrylated urethane with a polyol, and the hydrophilic compartment contains polyvinylalcohol.

33. The electrode of claim 2 for use as a potentiometric carbon dioxide electrode, wherein the internal reservoir contains bicarbonate salt and a pH sensitive redox salt.

34. The electrode of claim 33, wherein the internal reservoir also contains carbonic anhydrase.

35. The electrode of claim 33, wherein the pH sensitive redox salt is selected from the group of hydroquinone, benzoquinone, and combinations thereof.

36. The electrode of claim 33, wherein the membrane layer is in a substantially dry, inactive condition and convertible into a wet-up, active condition by exposure to an aqueous fluid and the bicarbonate salt is loaded into the dry internal reservoir in an amount to give a concentration in the range of 50 mM to 800 mM after wet up.

37. The electrode of claim 1 for use as a potentiometric carbon dioxide electrode, wherein the hydrophobic compartment contains acrylated siloxane and the hydrophilic compartment contains polyvinylalcohol.

38. The electrode of claim 2 for use in an electrochemical sensing apparatus for the analysis of an enzyme substrate in an aqueous sample, wherein the internal reservoir contains an enzyme and a redox salt.