Device for separating electrolyte chambers within an electrochemical sensor

Abstract

The present invention is drawn generally to an improved electrochemical sensor. The reference cell within the sensor can be a salt bridge comprising at least two chambers for containing an electrolyte fluid, preferably containing a semipermeable plug impregnated with an electrolyte, an essentially fluid impermeable plug for separating the at least two chambers, and a narrow opening through the plug providing a non-axial flow path for ionic communication between the at least two chambers when the electrolyte fluid is present. The invention is also drawn to a reference cell grounding system and method of grounding a reference cell.

What is claimed is:  
     
         1 . A reference cell grounding system for use as part of an electrochemical sensor, comprising: 
 (a) a semipermeable plug having a first end;    (b) a continuous electrolyte fluid within the semipermeable plug, said first end configured for contacting the continuous electrolyte fluid with a fluid specimen;    (c) an electrolyte sensing element displaced from the first end, said electrolyte sensing element comprising a metal ion-containing half-cell in ionic communication with the continuous electrolyte fluid; and    (d) a grounding member comprising a metal material that is more noble than the metal-ion of the half-cell, said grounding member being configured for electrical communication with the fluid specimen through the continuous electrolyte fluid, but not configured for direct contact with the fluid specimen.    
     
     
         2 . The reference cell of  claim 1  wherein the semipermeable plug comprises at least two semipermeable plugs divided by a channeled plug, said channeled plug comprising an impermeable material, wherein the channel of the channeled plug is filled with the continuous electrolyte fluid, thereby providing for electrical communication through the channel.  
     
     
         3 . The reference cell of  claim 2  further comprising an orientation axis defined by the shortest distance between the at least two semipermeable plugs, and wherein the channel of the channeled plug provides a non-axial flow path between the at least two semipermeable plugs with respect to the orientation axis.  
     
     
         4 . The reference cell of  claim 3  wherein the non-axial flow path is linear.  
     
     
         5 . The reference cell of  claim 3  wherein the non-axial flow path is confined within the body of the channeled plug.  
     
     
         6 . The reference cell of  claim 3  further comprising at least two narrow openings through the plug.  
     
     
         7 . The reference cell of  claim 3  wherein said channeled plug comprises a first barrier having a fluid directing surface and a second barrier having a fluid blocking surface, said fluid directing surface and said fluid blocking surface being mated such that said non-axial flow path is formed.  
     
     
         8 . The reference cell of  claim 7  wherein the first barrier and the second barrier are a pair of discs, each having axially centered bores, and wherein one of the discs has a larger outer diameter and a larger bore diameter than the opposing disc.  
     
     
         9 . The reference cell of  claim 8  wherein the fluid directing surface comprises an array of radially symmetrical open channels extending from the bore to the outer diameter.  
     
     
         10 . The reference cell of  claim 8  further comprising a housing and a concentrically positioned multiple ion sensor configured for retaining the continuous electrolyte fluid, wherein the bore of each of the discs is large enough to allow the multiple ion sensor to pass therethrough, and the outer diameter of each of the discs is large enough to fit within the housing.  
     
     
         11 . The reference cell of  claim 10  wherein one of the pair of discs fits snugly against the multiple ion sensor, and wherein the opposing disc fits snugly against the housing.  
     
     
         12 . The reference cell of  claim 1  wherein the semipermeable plugs comprise wood.  
     
     
         13 . The reference cell of  claim 1  wherein the semipermeable plugs are impregnated with the continuous electrolyte fluid prior to assembly.  
     
     
         14 . The reference cell of  claim 8  wherein said first barrier further comprises a surface having a series of concentric ridges which press into one of said semipermeable plugs, and wherein said second barrier further comprises a surface having a series of concentric ridges which press into a different semipermeable plug, such that any poisons that migrate into the semipermeable plug do not substantially migrate to the non-axial flow path.  
     
     
         15 . The reference cell of  claim 1  wherein the metal ion-containing half-cell is Ag/AgCl and the metal material of the grounding member is selected from the group consisting of gold, platinum, and platinum group metals.  
     
     
         16 . The reference cell of  claim 1  wherein the metal ion-containing half-cell is Pt/Hg 2 Cl 2  and the metal material of the grounding member is selected from the group consisting of gold, platinum, iridium, osmium, palladium, rhodium, ruthenium, silver, copper, and high alloy steels.  
     
     
         17 . A method of grounding a reference cell with respect to a fluid specimen in an electrochemical sensor, comprising: 
 (a) establishing an electrical potential between a metal ion-containing half-cell and a fluid specimen through a continuous electrolyte fluid; and    (b) establishing a ground to the fluid specimen through the continuous electrolyte fluid without direct contact between a metal grounding element and the fluid specimen, said metal grounding element comprising a metal that is more noble than the metal ion of the half-cell.    
     
     
         18 . The method of  claim 17  wherein reference cell comprises at least two semipermeable plugs impregnated with the electrolyte fluid, said at least two semipermeable plugs being separated by a channeled plug, said channeled plug comprising an impermeable material, wherein the channel of the channeled plug is filled with the continuous electrolyte fluid, thereby providing for electrical communication through the channel.  
     
     
         19 . The method of  claim 18  further comprising an orientation axis defined by the shortest distance between the at least two semipermeable plugs, and wherein the channel of the channeled plug provides a non-axial flow path between the at least two semipermeable plugs with respect to the orientation axis.  
     
     
         20 . The method of  claim 19  wherein the non-axial flow path is linear.  
     
     
         21 . The method of  claim 19  wherein the non-axial flow path is confined within the body of the channeled plug.  
     
     
         22 . The method of  claim 19  further comprising at least two narrow openings through the channeled plug.  
     
     
         23 . The method of  claim 19  wherein said channeled plug comprises a first barrier having a fluid directing surface and a second barrier having a fluid blocking surface, said fluid directing surface and said fluid blocking surface being mated such that said non-axial flow path is formed.  
     
     
         24 . The method of  claim 23  wherein the first barrier and the second barrier are a pair of discs, each having axially centered bores, and wherein one of the discs has a larger outer diameter and a larger bore diameter than the opposing disc.  
     
     
         25 . The method of  claim 24  wherein the fluid directing surface comprises an array of radially symmetrical open channels extending from the bore to the outer diameter.  
     
     
         26 . The reference cell of  claim 17  wherein the semipermeable plugs comprise wood.  
     
     
         27 . The method of  claim 18  further comprising the preliminary step of impregnating the continuous electrolyte fluid into the at least two semipermeable plugs prior to assembly.  
     
     
         28 . The method of  claim 24  wherein said first barrier further comprises a surface having a series of concentric ridges which press into one of said semipermeable plugs, and wherein said second barrier further comprises a surface having a series of concentric ridges which press into a different semipermeable plug, such that any poisons that migrate into the semipermeable plug do not substantially migrate to the non-axial flow path.  
     
     
         29 . The method of  claim 17  wherein the metal ion-containing half-cell is Ag/AgCl and the metal material of the grounding member is selected from the group consisting of gold, platinum, iridium, osmium, palladium, rhodium, and ruthenium.  
     
     
         30 . The method of  claim 17  wherein the metal ion-containing half-cell is Pt/Hg 2 Cl 2  and the metal material of the grounding member is selected from the group consisting of gold, platinum group metals, silver, copper, and high alloy steels.