Reference electrode

• US 20030029722A1
• Filed: 03/07/2002
• Published: 02/13/2003
• Est. Priority Date: 03/07/2001
• Status: Active Grant

• Current Assignee: Instrumentation Lab Co (Instrumentation Lab)
• Original Assignee: Instrumentation Lab Co (Instrumentation Lab)
• Inventors: Cosofret, Vasile V., Erdosy, Miklos
• Granted Patent: US 6,896,793 B2
• Time in Patent Office: Days
• US Class Current: 204/435
• CPC Class Codes: G01N 27/401 Salt-bridge leaks; Liquid junctions
• CPC Class Codes: G01N 33/4915 using flow cells flow cytometry G01N15/14

Abstract

The invention relates to a durable and reliable miniature liquid junction reference electrode for use with at least one electrode (e.g., an electrochemical sensor cartridge) for measuring certain characteristics of a fluid sample such as blood or other body fluid.

Claims

1. A reference electrode comprising:

(a) a reference sensor;

(b) a bridge electrolyte channel in fluid communication with said reference sensor; and

(c) a connector channel connected to the bridge electrolyte channel via a bridge electrolyte port, said connector channel comprising a sample inlet channel and a sample outflow channel through which a sample may flow, and a bridge electrolyte well for retaining a volume of a bridge electrolyte solution;

wherein said bridge electrolyte well is shaped to provide a liquid junction between the sample and the bridge electrolyte solution.

2. The reference electrode of claim 1, wherein the liquid junction comprises a surface area in the range of about 0.5 mm² to about 10 mm².

3. The reference electrode of claim 1, wherein said reference sensor comprises:

(a) a support substrate;

(b) a silver layer (Ag) deposited on said support substrate;

(c) a silver chloride (AgCl) layer deposited on said Ag layer;

(d) a glaze layer deposited on at least part of said AgCl layer; and

(e) a gasket disposed on said glaze layer.

4. The reference electrode of claim 3, wherein said support substrate comprises a polymeric material and/or a ceramic material.

5. The reference electrode of claim 4, wherein said polymeric material comprises polyvinyl chloride (PVC), polyethylene, polycarbonate, polyacrylate and/or polyimide.

6. The reference electrode of claim 4, wherein said ceramic material comprises aluminum oxide and/or silicium dioxide.

7. The reference electrode of claim 3, wherein one or more of said layers are screen printed layers or vapor deposited layers.

8. The reference electrode of claim 3, wherein said Ag layer is at least about 1 μ

m to about 15 μ

m thick.

9. The reference electrode of claim 3, wherein said Ag layer is at least about 1 μ

m thick.

10. The reference electrode of claim 3, wherein said AgCl layer is deposited on said Ag by electrodeposition on said Ag with a chloride electrolyte solution of between about 0.01 M and 1.0 M at a current density of between about 0.005 and about 0.5 mA/mm² for about 30 seconds to about 20 minutes.

11. The reference electrode of claim 10, wherein said chloride electrolyte solution comprises NaCl, KCl, and/or CaCl₂.

12. The reference electrode of claim 11, wherein said chloride electrolyte solution has a pH range of about pH 1 to about pH 7, about pH 1 to about pH 5, or about pH 1 to pH 2.

13. The reference electrode of claim 3, wherein said glaze layer comprises alumina and/or silica.

14. The reference electrode of claim 13, wherein said glaze layer is at least about 10 μ

m thick.

15. The reference electrode of claim 14, wherein said glaze layer has a thickness of between about 10 μ

m and about 500 μ

m.

16. The reference electrode of claim 3, wherein said gasket layer comprises polyurethane, silicone rubber, PVC, viton®

, natural rubber and/or synthetic rubber.

17. The reference electrode of claim 15, wherein said gasket is at least about 50 μ

m thick.

18. The reference electrode of claim 1, wherein said connector channel comprises a polymeric or metallic material that does not react with, or dissolve in, said bridge electrolyte solution.

19. The reference electrode of claim 18, wherein said polymeric material is a molded or machinable plastic.

20. The reference electrode of claim 19, wherein said polymeric material comprises acrylic, plexiglas®

, lexan®

, polycarbonate, and/or PVC.

21. The reference electrode of claim 18, wherein said metallic material comprises stainless steel, aluminum and/or platinum.

22. The reference electrode of claim 1, wherein said bridge electrolyte well is a round bottom well.

23. The reference electrode of claim 1, wherein said bridge electrolyte well is a flat bottom well.

24. The reference electrode of claim 1, wherein said bridge electrolyte well is a cone-shaped well.

25. The reference electrode of claim 1, wherein at least one of said sample outflow channel and said sample inlet channel each form a tilt angle of about 90°

to about 180°

relative to the longitudinal axis of the bridge electrolyte channel.

26. The reference electrode of claim 1, wherein said connector channel is located at a distance range from the reference sensor of between about 2 mm to about 10 mm, between about 2 mm to about 15 mm, or between about 2 mm to about 30 mm.

27. The reference electrode of claim 1, wherein said sample inlet channel is about 1 mm in diameter.

28. The reference electrode of claim 1, wherein said bridge electrolyte channel is about 0.5 mm in diameter.

29. The reference electrode of claim 27, wherein said bridge electrolyte channel is about 0.5 mm in diameter.

30. The reference electrode of claim 1, wherein said sample outflow channel is about 2 mm in diameter.

31. The reference electrode of claim 27, wherein said sample outflow channel is about 2 mm in diameter.

32. The reference electrode of claim 28, wherein said sample outflow channel is about 2 mm in diameter.

33. The reference electrode of claim 1, wherein said sample outflow channel and said sample inlet channel comprise a flexible tube that is about 1 mm to about 20 mm in diameter.

34. The reference electrode of claim 1, wherein said bridge electrolyte solution comprises KCl saturated with AgCl, with a chloride ion solution of about 0.1 M to about 0.5 M at the temperature said solution is stored and used.

35. A method for using a liquid junction reference electrode, comprising the steps of:

(a) providing a reference electrode comprising a reference sensor;

a bridge electrolyte channel in fluid communication with said reference sensor; and

a connector channel connected to the bridge electrolyte channel via a bridge electrolyte port, said connector channel comprising a sample inlet channel and a sample outflow channel through which a sample may flow, and a bridge electrolyte well for retaining a volume of a bridge electrolyte solution;

wherein said bridge electrolyte well is shaped to provide a liquid junction between the sample and the bridge electrolyte solution.

(b) providing a calibrating solution or a sample to said sample inlet channel;

(c) providing a bridge electrolyte solution to said bridge electrolyte inlet;

(d) providing a force to said sample so that it flows toward said bridge electrolyte port;

(e) providing a force to said bridge electrolyte solution so that it flows toward said bridge electrolyte port;

(f) forming a liquid junction between said sample and said bridge electrolyte solution at said bridge electrolyte well with a surface area in the range of about 1 mm² to about 10 mm²; and

(g) taking a measurement.