ELECTRO-CHEMICAL SENSOR

• US 20120268134A1
• Filed: 10/14/2010
• Published: 10/25/2012
• Est. Priority Date: 12/09/2009
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Lafitte, Valerie, Lawrence, Nathan S.
• Granted Patent: US 9,377,434 B2
• Time in Patent Office: Days
• US Class Current: 324/324
• CPC Class Codes: G01N 27/3335 the membrane containing at least one organic component G01N27/3271 takes precedence; aspects concerning the enzyme reagent in enzyme electrodes C12Q1/001
• CPC Class Codes: G01N 33/18 Water

Abstract

An electrochemical sensor for the presence or concentration of an analyte has at least one electrode and at least one electrochemically active species able to undergo electrochemical reaction in response to electrical potential applied to the electrode, where the said reaction is modified by the presence of the analyte. This sensor has the novel characteristic that at least one said electrochemically active species is encapsulated within polymer particles. These particles are preferably formed from an amorphous polymer with a glass transition temperature above the temperature of the fluid to which the sensor is exposed. The encapsulating polymer protects the analyte species from degradation, but a small analyte such as a hydrogen or bisulfide ion can pass through the polymer and undergo reaction at the active species.

Claims

1. An electrochemical sensor comprising at least one electrode and at least one electrochemically active species able to undergo electrochemical reaction in response to electrical potential applied to the electrode, said reaction being modified by the presence of an analyte species,

characterised in that at least one said electrochemically active species is encapsulated within polymer particles.

2. An electrochemical sensor according to claim 1 comprising a solid substrate to which at least one said encapsulated electrochemically active species is immobilised.

3. An electrochemical sensor according to claim 2 wherein the substrate is electrically insulating and the encapsulated species is immobilized proximate to a said electrode.

4. An electrochemical sensor according to claim 2 wherein a said electrode comprises an electrically conductive solid body and the encapsulated species is immobilized thereon.

5. An electrochemical sensor according to claim 2 wherein the substrate is electrically conductive and comprises carbon.

6. An electrochemical sensor according to claim 1 preceding claims comprising at least one further electrode which is electrically insulated from the first said electrode.

7. An electrochemical sensor according to claim 1 wherein the polymer has a glass transition temperature above 80°

C.

8. An electrochemical sensor according to claim 1 wherein the polymer has a glass transition temperature above 120°

C.

9. An electrochemical sensor according to claim 1 wherein the polymer comprises benzene rings joined through sulfone groups.

10. An electrochemical sensor according to claim 1 wherein the electrochemically active species is/are one or more molecules capable of undergoing reversible oxidation and reduction reactions brought about through application of electrical potential to the electrodes.

11. An electrochemical sensor according to claim 10 wherein an oxidation and or reduction reaction displays a potentiometric shift dependant on concentration of an analyte.

12. An electrochemical sensor according to claim 11 wherein the analyte is hydrogen ion or bisulfide ion.

13. An electrochemical sensor according to claim 10 comprising at least two encapsulated species capable of undergoing reversible oxidation and reduction reactions brought about through application of electrical potential to the electrodes, where a said oxidation and/or reduction reaction of one species displays a potentiometric shift dependant on concentration of an analyte and a said oxidation and/or reduction reaction of another species takes place at a potential which is independent of the concentration of that analyte.

14. An electrochemical sensor according to claim 1 wherein the polymer particles comprise a multiplicity of islands of the electrochemically active species, distributed within a continuous matrix of the polymer.

16. An electrochemical sensor according to claim 1 together with means to apply variable voltage to the sensor and measure current while the voltage is varied.

17. A downhole tool for measuring an analyte concentration in a wellbore fluid, comprising an electrochemical sensor in accordance with claim 1.

18. A method of measuring an analyte concentration in a fluid, comprising exposing a sensor according to claim 1 to the fluid, the encapsulating polymer having a glass transition temperature above the temperature of the fluid, and applying varying potential to the sensor while observing current flow.

19. A method according to claim 18 carried out at a location below ground.

20. A method according to claim 18 carried out downhole in a wellbore.

15. An electrochemical sensor comprising an insulating body, at least two electrodes supported by the body and electrically insulated from each other and at least one electrochemically active species able to undergo electrochemical reaction in response to electrical potential applied to the electrodes, said reaction being modified by the presence of an analyte species, characterised in that at least one said electrochemically active species is encapsulated within polymer particles and the particles are immobilized relative to the insulating body.