Reference Electrode and Combined Electrode

• US 20120098544A1
• Filed: 02/03/2010
• Published: 04/26/2012
• Est. Priority Date: 04/21/2009
• Status: Active Grant

• Current Assignee: Timothy Russell
• Original Assignee: Timothy Russell
• Inventors: Russell, Timothy
• Granted Patent: US 9,128,043 B2
• Time in Patent Office: Days
• US Class Current: 324/438
• CPC Class Codes: G01N 27/301 Reference electrodes
• CPC Class Codes: G01N 27/401 Salt-bridge leaks; Liquid junctions

Abstract

A reference electrode comprises an outside wall which acts as a boundary between electrolyte and sample solution, which outside wall comprises a resin which is ionically conducting, non-porous and salt-loaded, and a barrier through which no electrochemical communication between the electrolyte and sample solution is possible. A window is present in said barrier thereby allowing electrochemical communication between the electrolyte and the sample solution through the resin at said window. The reference electrode can be suitable for use with a separate measuring electrode, or can be combined with a measuring electrode in a single unit electrode assembly.

Claims

1. A reference electrode for use with a measuring electrode for measuring ion activity in a sample solution, comprising:

an electrode chamber for holding electrolyte and an electrode element in said electrode chamber,

an outside wall of said reference electrode, providing a boundary between the electrolyte and the sample solution,

a resin layer on the interior or exterior of said electrode chamber, which is ionically conducting, non-porous and salt-loaded, and

a barrier layer on the interior or exterior of said electrode chamber, through which no electrochemical communication between the electrolyte and sample solution is possible,

wherein a window is present in said barrier thereby allowing electrochemical communication between the electrolyte in said electrode chamber and the sample solution through the resin at said window.

2. A reference electrode as claimed in claim 1 wherein the outside wall of said reference electrode is in tubular form.

3. A reference electrode as claimed in claim 1 wherein said barrier is an inner layer of said outside wall and said resin is an outer layer of said outside wall.

4. A reference electrode as claimed in claim 1 wherein said resin is an immobilized non-porous polymer having one or more salts of potassium, sodium and/or lithium mixed through said polymer before curing of the polymer to render it electrically conductive, said polymer providing a physical barrier between the electrolyte and the sample solution but permitting electrochemical communication between them.

5. A reference electrode as claimed in claim 1 wherein said resin is an electroconductive material containing one or more dispersed salts selected from the group consisting of chloride, nitrate, sulphate and bromide salts of potassium, sodium and lithium.

6. A reference electrode as claimed in claim 1 wherein said resin is prepared by a vertical casting method.

7. A combined electrode comprising a reference electrode as claimed in claim 1 and a measuring electrode in a single-unit electrode assembly.

8. A combined electrode as claimed in claim 7 in the form of an elongate tube wherein the measuring electrode is positioned centrally along the longitudinal axis and the reference electrode chamber takes the form of a sleeve, of annular cross-section, around said measuring electrode.

9. A combined electrode as claimed in claim 8 wherein the measuring electrode is fitted inside a tube on the outside wall of the reference electrode so as to define an annular reference electrode chamber between them to hold reference electrolyte, with the measuring electrode as the radially-inner wall and the tube on the outside wall of the reference electrode as the radially outer wall of the chamber, and a reference electrode element housed in said chamber.

10. A combined electrode as claimed in claim 9 wherein the base of the reference electrode chamber is sealed.

11. A combined electrode as claimed in claim 8 wherein the measuring electrode is fitted inside a tube of said barrier, which tube is sealed at its bottom end by a seal and by a portion of said resin so as to define an annular reference electrode chamber between said barrier and said measuring electrode and to hold reference electrolyte, with the measuring electrode as the radially-inner wall and the tube of the barrier as the radially outer wall of the chamber, and comprising a reference electrode element housed in said chamber.

12. An electrode as claimed in claim 1 wherein the reference electrode is an Ag/AgCl reference electrode.

13. An electrode as claimed in claim 1 wherein the resin comprises a vinyl ester polymer.

14. An electrode as claimed in 1 claim which is configured for measuring pH.

15. A method of making a polymeric material suitable for use as the outside wall of a reference electrode, comprising:

vertically orientating a mold which is substantially cylindrical and closed at its bottom end;

casting a salt-containing uncured polymer into said mold;

fitting one or more sleeve(s) of barrier material onto a central cylindrical inert core;

placing said core, carrying said sleeve(s), substantially centrally into said mold, thereby displacing the salt-containing uncured polymer so that said salt-containing uncured polymer occupies a gap between said sleeve-carrying core and the internal surface of the mold;

curing the polymer whilst said mold is in a position so that its longitudinal position is substantially vertical;

removing the mold and the central cylindrical inert core;

and optionally cutting off part of the base of the cured material.

16. A method as claimed in claim 15 wherein the mold is test-tube shaped.

17. A method of making an electrode comprising the method steps of claim 15.

18-19. -19. (canceled)