Ion exchange membranes and dissolved gas sensors

Abstract

Ion exchange membranes for use in sensors that measure dissolved gases are described. Sensors constructed using the disclosed membranes are able to maintain electrolyte conditions within the electrolyte volume so as to have greatly extended and more stable lifetimes than sensors of similar construction and electrolyte volume constructed with standard membranes.

1 . A method of preparing a gas permeable membrane comprising a guanidinium salt, the method comprising preparing a solvent comprising the guanidinium salt and imbibing a porous support polymer with the solvent.  
     
     
         2 . The method of  claim 1 , wherein the membrane comprises a supported liquid membrane.  
     
     
         3 . The method of  claim 1 , wherein the porous support polymer comprises polytetrafluoroethylene.  
     
     
         4 . The method of  claim 1 , wherein the porous support polymer comprises poly(vinyl chloride).  
     
     
         5 . The method of  claim 4 , further comprising plasticizing the polymer for use as the membrane.  
     
     
         6 . The method of  claim 4 , further comprising plasticizing the polymer, wherein the polymer is high molecular weight poly(vinyl chloride) and plasticizing is effected with a solvent selected from the group consisting adipate esters, sebacate esters, phthalate esters, glycol esters, low volatility ethers, trimellitic acid esters, phosphate triesters, chlorinated paraffins, and mixtures thereof.  
     
     
         7 . The method of  claim 1 , wherein the solvent comprises from 0.1% to 10% by weight of the guanidinium salt.  
     
     
         8 . The method of  claim 7  further defined as preparing a solvent comprising 1% to 5% by weight guanidinium salt.  
     
     
         9 . The method of  claim 1 , wherein the guanidinium salt has the formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl, cycloalkenyl, substituted cycloalkenyl, alkynyl, aryl, substituted aryl, heteroaryl and substituted heteroaryl, and X −  is an anion.  
     
     
         10 . The method of  claim 9 , wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  are independently selected from the group consisting of hydrogen, C1-30 alkyl, and aryl, and X −  is selected from the group consisting of chloride, bromide, fluoride, iodide, hydroxide, acetate, carbonate, sulfate and nitrate and combinations thereof.  
     
     
         11 . A method of preparing an amperometric gas sensor, the method comprising selecting a guanidinium salt, preparing a solvent containing the guanidinium salt, imbibing a gas permeable membrane with the solvent, forming a reversible anode and an inert cathode, applying an electrolyte solution over the anode and the cathode, allowing the solution to evaporate and covering both electrodes with the gas permeable membrane, such that the membrane prevents communication between the electrolyte and an ambient environment except through the membrane.  
     
     
         12 . The method of  claim 11 , wherein the inert cathode is selected from the group consisting of gold, platinum, silver, palladium, iridium, rhodium, ruthenium, osmium and alloys thereof and the reversible anode is selected from the group consisting of silver/silver halide, lead/lead sulfate, sliver/silver oxide-hydroxide and lead/lead oxide-hydroxide.  
     
     
         13 . The method of  claim 12 , wherein the inert cathode is gold and the reversible anode is a silver/silver chloride electrode.  
     
     
         14 . The method of claim sensor of  claim 11 , wherein the gas permeable membrane is a supported liquid membrane.  
     
     
         15 . The method of  claim 11 , further comprising plasticizing a polymer to form the membrane.  
     
     
         16 . A method of measuring dissolved gas in a liquid sample the method comprising removing an ionic product of an electrode reaction from an electrolyte volume using a guanidinium salt and transporting an ion consumed in the electrode reaction from the liquid sample into the electrolyte volume.  
     
     
         17 . The method of  claim 16  wherein the ionic product is hydroxide ion and the ion consumed in the electrode reaction is chloride.  
     
     
         18 . The method of  claim 16 , wherein the liquid sample comprises seawater, a biological fluid or a foodstuff.  
     
     
         19 . A solid state amperometric gas sensor, comprising: 
 a gas-permeable membrane comprising a guanidinium salt;    an electrolyte salt in contact with the gas-permeable liquid membrane through a first surface of the electrolyte salt; and    a pair of electrodes in contact with a second, opposite surface of the electrolyte salt.    
     
     
         20 . The sensor of  claim 19  where the gas-permeable membrane is a supported liquid membrane.  
     
     
         21 . The sensor of  claim 19  where the gas-permeable membrane comprises a plasticized polymer.  
     
     
         22 . The sensor of  claim 19  where the electrolyte salt is selected from the group consisting of Group I metal halides.  
     
     
         23 . The sensor of  claim 22  where the electrolyte salt is selected from KCl and NaCl and mixtures thereof.  
     
     
         24 . A dissolved oxygen sensor, comprising: 
 a gas permeable membrane, other than a supported liquid membrane, the membrane comprising a guanidinium salt;    an inert cathode; and    a reversible anode.    
     
     
         25 . The dissolved oxygen sensor of  claim 24  further comprising an electrolyte where the cathode and anode are imprinted on an oxygen impervious, insulating substrate, the electrolyte is in contact with the cathode and anode and the gas-permeable membrane prevents communication between the electrolyte and an external medium.  
     
     
         26 . A gas permeable membrane comprising a guanidinium salt, and a plasticized polymer, wherein the plasticized polymer is high molecular weight poly(vinyl chloride) plasticized with a solvent selected from the group consisting adipate esters, sebacate esters, phthalate esters, glycol esters, low volatility ethers, trimellitic acid esters, phosphate triesters, chlorinated paraffins, and mixtures thereof.  
     
     
         27 . The membrane of  claim 26  comprising a supported liquid membrane.  
     
     
         28 . The membrane of  claim 26  comprising from 0.1% to 10% by weight of the guanidinium salt.  
     
     
         29 . The membrane of  claim 26  comprising 1% to 5% by weight of the guanidinium salt.  
     
     
         30 . The membrane of  claim 26 , wherein the guanidinium salt has the formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are independently selected from the group consisting of substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl, cycloalkenyl, substituted cycloalkenyl, alkynyl, substituted aryl, heteroaryl and substituted heteroaryl, and X −  is an anion.  
     
     
         31 . The gas permeable membrane of  claim 30 , wherein X −  is selected from the group consisting of chloride, bromide, fluoride, iodide, hydroxide, acetate, carbonate, sulfate and nitrate and combinations thereof.  
     
     
         32 . The gas permeable membrane of  claim 30 , wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are independently selected from the group consisting of hydrogen, C1-30 alkyl, and aryl, and X −  is selected from the group consisting of chloride, bromide, fluoride, iodide, hydroxide, acetate, carbonate, sulfate and nitrate and combinations thereof.  
     
     
         33 . An amperometric gas sensor comprising a gas-permeable membrane comprising a guanidinium salt, an inert cathode and a reversible anode, the inert cathode selected from the group consisting of silver, palladium, iridium, rhodium, ruthenium, and osmium and alloys thereof and the reversible anode is selected from the group consisting of lead/lead sulfate, sliver/silver oxide-hydroxide and lead/lead oxide-hydroxide.  
     
     
         34 . The sensor of  claim 33 , wherein the gas permeable membrane comprises a supported liquid membrane.  
     
     
         35 . The sensor of  claim 34 , wherein the gas permeable membrane comprises a plasticized polymer.  
     
     
         36 . The sensor of  claim 34 , wherein the guanidinium salt removes an ionic product of an electrode reaction from an electrolyte volume and transports an ion consumed in the electrode reaction from the sample into the electrolyte volume.  
     
     
         37 . The sensor of  claim 36 , wherein the ionic product is hydroxide ion and the ion consumed in the electrode reaction is chloride.  
     
     
         38 . A method of preparing an amperometric gas sensor, the method comprising selecting a guanidinium salt, preparing a solvent containing the guanidinium salt, imbibing a gas permeable membrane with the solvent, forming a reversible anode and a suitable inert cathode, applying an electrolyte layer to and covering both electrodes with the gas permeable membrane, such that the membrane prevents communication between the outer electrolyte and an ambient environment.  
     
     
         39 . The method of  claim 38 , wherein the electrolyte layer is a hydrogel.  
     
     
         40 . The method of  claim 39 , wherein the hydrogel is selected from the group consisting of gelatin, cellulose nitrate, cellulose, agar and agarose.  
     
     
         41 . The method of  claim 39  wherein the hydrogel is selected from the group consisting of cross-linked acrylates, methyl methacrylates, methacrylates, hyroxyalkyl acrylates, hydroxyalkyl(meth)acrylates and acrylamides.  
     
     
         42 . The sensor of  claim 19 , wherein the electrolyte salt comprises a hydrogel.  
     
     
         43 . The sensor of  claim 42  wherein the bydrogel is selected from the group consisting of cross-linked acrylates, methyl methacrylates, methacrylates, hyroxyalkyl acrylates, hydroxyalkyl(meth)acrylates and acrylamides.  
     
     
         44 . An amperometric gas sensor, comprising; 
 an anode and a cathode deposited on a gas-impervious substrate;    an electrolyte between the anode and the cathode, and    a gas-permeable membrane comprising a guanidinium salt covering the anode, the cathode and the electrolyte.    
     
     
         45 . The sensor of  claim 44 , further comprising a well surrounding the anode and the cathode, wherein the gas permeable membrane covers the well and defines an electrolyte volume within the well.  
     
     
         46 . The sensor of  claim 45 , wherein the well defining the electrolyte volume comprises a laminate material having a hole, wherein the hole is placed over the anode and the cathode.  
     
     
         47 . The sensor of  claim 44 , further comprising a guard ring deposited on the gas-impervious substrate, wherein the gas permeable membrane also covers the guard ring.  
     
     
         48 . The sensor of  claim 44 , wherein the electrolyte comprises a solid salt.  
     
     
         49 . The sensor of  claim 44 , wherein the electrolyte comprises a hydrogel.  
     
     
         50 . The sensor of  claim 44 , wherein the gas-permeable membrane comprises a supported liquid membrane.  
     
     
         51 . The sensor of  claim 50 , wherein the supported liquid membrane comprises a porous support polymer comprising a solvent.  
     
     
         52 . The sensor of  claim 51 , wherein the porous support polymer comprises a polytetrafluoroethylene membrane and the solvent is selected from the group consisting of o-nitrophenyl octyl ether and dioctyl adipate, and mixtures thereof.  
     
     
         53 . The sensor of  claim 50 , wherein the supported liquid membrane comprises a plasticized polymer.  
     
     
         54 . The sensor of  claim 53 , wherein the plasticized polymer comprises poly(vinyl chloride) and a phthalate plasticizer.  
     
     
         55 . The sensor of  claim 54 , wherein the plasticized polymer comprises a high molecular weight poly(vinyl chloride) plasticized with a solvent selected from the group consisting of o-nitrophenyl octyl ether and dioctyl adipate, and mixtures thereof.  
     
     
         56 . The sensor of  claim 44 , wherein the guanidinium salt is not covalently bonded to the membrane.  
     
     
         57 . The sensor of  claim 44 , wherein the electrolyte comprises a Group I metal halide.  
     
     
         58 . The sensor of  claim 57 , wherein the Group I metal halide comprises KCl, NaCl or a mixture thereof.  
     
     
         59 . The sensor of  claim 44 , wherein the guanidinium salt comprises 1% to 5% by weight of the membrane.  
     
     
         60 . The sensor of  claim 44 , wherein the guanidinium salt has the formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are independently selected from the group consisting of substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl, cycloalkenyl, substituted cycloalkenyl, alkynyl, substituted aryl, heteroaryl and substituted heteroaryl such that the salt has an affinity for the membrane and X −  is an anion.  
     
     
         61 . The sensor of  claim 60 , wherein X −  is selected from the group consisting of chloride, bromide, fluoride, iodide, hydroxide, acetate, carbonate, sulfate and nitrate and combinations thereof.  
     
     
         62 . The sensor of  claim 60 , wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are independently selected from the group consisting of hydrogen, C1-30 alkyl, and aryl.  
     
     
         63 . The sensor of  claim 49 , wherein the hydrogel is selected from the group consisting of cross-linked acrylates, methyl methacrylates, methacrylates, hydryxalkyl acrylates, hydroxyalkyl(meth)acrylates, acrylamides, silicone hydrogels, gelatin, cellulose nitrate, cellulose, agar, and agarose and combinations thereof.  
     
     
         64 . A method of making an amperometric gas sensor, comprising: 
 depositing an anode and a cathode onto a gas-impervious substrate;    placing an electrolyte between the anode and the cathode; and    covering the anode, the cathode and the electrolyte with a gas-permeable membrane, wherein the gas-permeable membrane comprises a guanidinium salt.    
     
     
         65 . The method of  claim 64 , wherein depositing comprises printing the anode and cathode onto the substrate using a method for printing circuit boards.  
     
     
         66 . The method of  claim 64  further comprising depositing a guard ring onto the substrate.  
     
     
         67 . The method of  claim 64  further comprising forming a well around the anode and the cathode and covering the well with the membrane to define an electrolyte volume.  
     
     
         68 . The method of  claim 67 , wherein placing an electrolyte between the anode and the cathode comprises adding the electrolyte to the well.  
     
     
         69 . The method of  claim 68 , wherein adding the electrolyte to the well comprises adding the electrolyte to the well as a solution.  
     
     
         70 . The method of  claim 69 , wherein the solution is allowed to dry.  
     
     
         71 . The method of  claim 68 , wherein adding the electrolyte to the well comprises forming a hydrogel in the well.  
     
     
         72 . The method of  claim 71 , wherein the hydrogel is selected from the group consisting of cross-linked acrylates, methyl methacrylates, methacrylates, hydryxalkyl acrylates, hydroxyalkyl(meth)acrylates, acrylamides, silicone hydrogels, gelatin, cellulose nitrate, cellulose, agar, and agarose and combinations thereof.  
     
     
         73 . The method of  claim 67 , wherein forming a well around the anode and the cathode comprises placing a laminating material comprising a hole onto the substrate such that the hole is disposed over the anode and cathode.  
     
     
         74 . The method of  claim 67 , wherein covering the well with the membrane comprises depositing a plasticized PVC membrane material dissolved in a volatile solvent over the well.  
     
     
         75 . The method of  claim 74 , further comprising first covering the well with a layer of microporous cellulose acetate and then depositing the PVC membrane material onto the microporous cellulose acetate.  
     
     
         76 . An amperometric gas sensor formed on a printed circuit board, comprising: 
 an inert cathode and a reversible anode patterned on a gas-impervious electrically-insulating substrate;    an electrolyte between the cathode and the anode; and    a gas-permeable membrane covering the cathode, the anode and the electrolyte; wherein the membrane is sealed at its outer edges to prevent communication between the electrolyte and a medium in which a gas is sensed except through the membrane.    
     
     
         77 . An amperometric gas sensor, comprising: 
 an inert cathode and a reversible anode printed on a gas-impervious circuit board substrate;    a well surrounding the cathode and the anode;    a hydrogel in the well, wherein the hydrogel comprises an electrolyte;    and a gas-permeable membrane covering the well, wherein the gas permeable membrane comprises a guanidinium salt.    
     
     
         78 . The sensor of  claim 77 , wherein the inert cathode is selected from the group consisting of gold, platinum, silver, palladium, iridium, rhodium, ruthenium and osmium, and alloys thereof; and the reversible anode comprises a material selected from the group consisting of silver/silver halide, lead/lead sulfate, silver/silver oxide hydroxide and lead/lead oxide-hydroxide.  
     
     
         79 . The sensor of  claim 78 , wherein the inert cathode comprises a material selected from the group comprising of gold and platinum and the reversible anode is an Ag/AgCl electrode.  
     
     
         80 . The sensor of  claim 77 , wherein the hydrogel is selected from the group consisting of cross-linked acrylates, methyl methacrylates, methacrylates, hydryxalkyl acrylates, hydroxyalkyl(meth)acrylates, acrylamides, silicone hydrogels, gelatin, cellulose nitrate, cellulose, agar, and agarose, and combinations thereof.