Electrochemical Tongue

Abstract

An electrochemical tongue can be used for detection of metal ions. The reference electrode of the electrochemical tongue can be coated with a polymer. More than one reference electrode can be used, and the electrochemical tongue can be inserted into a cone penetrometer for portable, in situ analysis.

What is claimed is: 
     
         1 . An electrochemical tongue, comprising:
 a) a reference electrode;   b) a counter electrode;   c) one or more working electrodes, wherein at least one of the one or more working electrodes is coated with a polymer or copolymer having the formula:   
       
         
           
           
               
               
           
         
         
           wherein X is independently NH or O; 
           r is independently an integer from approximately 1 to approximately 15; and 
           Y is a chelating agent; and 
         
         d) a potentiostat in electrical communication with the reference electrode, the counter electrode, and the one or more working electrodes. 
       
     
     
         2 . The electrochemical tongue of  claim 1 , wherein the electrochemical tongue has at least two working electrodes that are of distinct materials. 
     
     
         3 . The electrochemical tongue of  claim 1 , wherein at least one of the one or more working electrodes are formed from gold, carbon fiber, silver, platinum, and transparent conductive oxides. 
     
     
         4 . The electrochemical tongue of  claim 1 , wherein at least one of the one or more working electrodes are of glassy carbon, carbon paste, carbon fiber, carbon nanotubes, and graphene. 
     
     
         5 . The electrochemical tongue of  claim 1 , wherein at least one of the one or more working electrodes comprises conductive metal oxides coated on rigid or flexible substrates. 
     
     
         6 . The electrochemical tongue of  claim 2 , wherein at least one of the one or more working electrodes is coated with a polymer having the formula: 
       
         
           
           
               
               
           
         
         wherein X is NH or O; 
         r is an integer from approximately 1 to approximately 15; 
         n is an integer from approximately 6 to approximately 100; and 
         Y is a chelating agent. 
       
     
     
         7 . The electrochemical tongue of  claim 2 , wherein at least one of the at least two working electrodes is coated with a polymer having the formula: 
       
         
           
           
               
               
           
         
         wherein X is NH or O; 
         r is an integer from approximately 1 to approximately 15; 
         m is an integer from approximately 6 to approximately 100; 
         n is an integer from approximately 6 to approximately 100; and 
         Y is a chelating agent. 
       
     
     
         8 . The electrochemical tongue of  claim 1 , wherein the chelating agent Y is selected from the group consisting of an aminocarboxylic acid; a hydrocarboxylic acid; ethelene diamine; diethylenetriamine; triethylenetetramine; triaminotriethylamine; polyethyleneimine; triethanolamine; n-hydroxyethylethylene diamine; 2-aminopyridine; 4-aminopyridine; 2,2′ dipicolylamine; 5,6 diamino-1,10 phenanthroline; thioglycolic acid; gluthathione; and diethyl dithiophosphoric acid. 
     
     
         9 . The electrochemical tongue of  claim 8 , wherein the chelating agent Y is an aminocarboxylic acid. 
     
     
         10 . The electrochemical tongue of  claim 9  wherein the aminocarboxylic acid is selected from the group consisting of iminodiacetic acid and n-hydroxyethyl glycine. 
     
     
         11 . The electrochemical tongue of  claim 8 , wherein the chelating agent Y is a hydroxycarboxylic acid. 
     
     
         12 . The electrochemical tongue of  claim 11 , wherein the hydroxycarboxylic acid is selected from the group consisting of tartaric acid, citric acid, and gluconic acid. 
     
     
         13 . The electrochemical tongue of  claim 1 , further including a sensor selected from the group consisting of a voltammetric sensor, an amperometric sensor, and a potentiometric sensor. 
     
     
         14 . The electrochemical tongue of  claim 13 , wherein the sensor includes one or more of a linear sweep sensor, a cyclic sensor, a stair case sensor, a differential pulse sensor, a square wave sensor, and an anodic/cathodic stripping voltammetry sensor. 
     
     
         15 . The electrochemical tongue of  claim 13 , further including a potentiometric sensor. 
     
     
         16 . The electrochemical tongue of  claim 13 , further including one or more of a redox sensor, a pH sensor, an electrical conductivity/sensitivity sensor, a dissolved oxygen sensor, and a selective ion selective sensor. 
     
     
         17 . The electrochemical tongue of  claim 1 , further including a housing defining a passageway for the reference electrode, counter electrode, and one or more working electrodes. 
     
     
         18 . The electrochemical tongue of  claim 17 , wherein the housing is adapted for insertion into a penetrometer. 
     
     
         19 . The electrochemical tongue of  claim 17 , further including a porous portion that allows a sample to enter the electrochemical tongue. 
     
     
         20 . The electrochemical tongue of  claim 1 , wherein at least a portion of at least one of the one or more working electrodes include sensing surfaces that have been modified by at least one of gel integration and bismuth/mercury coating. 
     
     
         21 . The electrochemical tongue of  claim 1 , wherein the one or more of the working electrodes has an ionically conductive fluoropolymer overcoating. 
     
     
         22 . The electrochemical tongue of  claim 1 , further comprising a processor programmed to:
 i) receive a voltammetric response;   ii) filter and extract features;   iii) build a decision tree and a linear model; and   iv) display the identity of a metal ion.   
     
     
         23 . A method for performing voltammetry, comprising the steps of:
 a) contacting a sample to be analyzed with an electrochemical tongue that includes:
 i) a reference electrode; 
 ii) a counter electrode; 
 iii) one or more working electrodes, wherein at least one of the one or more working electrodes is coated with a polymer or copolymer having the formula: 
   
       
         
           
           
               
               
           
         
         
           
             wherein X is NH or O; 
             r is an integer from approximately 1 to approximately 15; and 
             Y is a chelating agent; and 
           
           iv) a potentiostat in electrical communication with the reference electrode, the counter electrode, and the one or more working electrodes; 
         
         b) applying a constant voltage across the one or more of the working electrodes to reduce the metal ion onto the surface of the electrode; and 
         c) increasing the voltage across one or more working electrode to oxidize and strip off the metal from the surface of the electrode. 
       
     
     
         24 . The method of  claim 23 , wherein the electrochemical tongue has at least two working electrodes of distinct materials to which the sample is contacted. 
     
     
         25 . The method of  claim 24 , wherein at least one of the one or more working electrodes are formed from gold, carbon fiber, silver, platinum, and transparent conductive oxides. 
     
     
         26 . The method of  claim 24 , wherein at least one of the one or more working electrodes to which a sample is contacted includes at least one carbon-based material selected from the group consisting of glassy carbon; carbon paste; carbon fiber; carbon nanotubes; and graphene. 
     
     
         27 . The method of  claim 24 , wherein at least one of the working electrodes to which a sample is contacted comprises conductive metal oxides coated on rigid or flexible substrates. 
     
     
         28 . The method of  claim 24 , wherein at least one of the at least two working electrodes to which a sample is contacted is coated with a polymer having the formula: 
       
         
           
           
               
               
           
         
         wherein X is NH or O; 
         r is an integer from approximately 1 to approximately 15; 
         n is an integer from approximately 6 to approximately 100; and 
         Y is a chelating agent. 
       
     
     
         29 . The method of  claim 23 , wherein at least one of the at least two working electrodes to which a sample is contacted is coated with a polymer having the formula: 
       
         
           
           
               
               
           
         
         wherein X is NH or O, 
         r is an integer from approximately 1 to approximately 15; 
         m is an integer from approximately 6 to approximately 100; 
         n is an integer from approximately 6 to approximately 100; and 
         Y is a chelating agent. 
       
     
     
         30 . The method of  claim 23 , wherein the chelating agent Y coating the one or more working electrodes to which a sample is in contact is selected from the group consisting of an aminocarboxylic acid; a hydrocarboxylic acid; ethelene diamine; diethylenetriamine; triethylenetetramine; triaminotriethylamine; polyethyleneimine; triethanolamine; n-hydroxyethylethylene diamine; 2-aminopyridine; 4-aminopyridine; 2,2′ dipicolylamine; 5,6 diamino-1,10 phenanthroline; thioglycolic acid; gluthathione; and diethyl dithiophosphoric acid. 
     
     
         31 . The method of  claim 30 , wherein the chelating agent Y coating the one or more working electrodes to which a sample is in contact is an aminocarboxylic acid. 
     
     
         32 . The method of  claim 31  wherein the aminocarboxylic acid is selected from the group consisting of iminodiacetic acid and n-hydroxyethyl glycine. 
     
     
         33 . The method of  claim 30 , wherein the chelating agent Y coating the one or more working electrodes to which a sample is in contact is a hydroxycarboxylic acid. 
     
     
         34 . The method of  claim 33 , wherein the hydroxycarboxylic acid is selected from the group consisting of tartaric acid, citric acid, and gluconic acid. 
     
     
         35 . The method of  claim 23 , further comprising the steps of:
 d) measuring a first sampling current that flows through the one or more working electrodes during a predetermined interval in which the pulse voltage is not applied;   e) measuring a second sampling current that flows through the one or more working electrodes while the pulse voltage is applied; and   f) calculating the difference between the first and second sampling currents.   
     
     
         36 . A method for performing voltammetry, comprising the steps of:
 a) contacting a sample to be analyzed with an electrochemical tongue that includes:
 i) a reference electrode; 
 ii) a counter electrode; 
 iii) one or more working electrodes, wherein at least one of the one or more working electrodes is coated with a polymer or copolymer having the formula: 
   
       
         
           
           
               
               
           
         
         
           
             wherein X is NH or O; 
             r is an integer from approximately 1 to approximately 15; and 
             Y is a chelating agent; and 
           
           iv) a potentiostat in electrical communication with the reference electrode, the counter electrode, and the one or more working electrodes; 
         
         b) ramping the working electrode voltage linearly versus time to either positive or negative voltages.