Electrochemical detection of nitro-containing compounds

Abstract

A carbon electrode having a functional moiety that forms a charge-transfer complex with a nitro-containing compound covalently attached to a surface of the electrode, and a process of preparing such an electrode are provided. Also provided are sensing systems integrating the carbon electrode and methods utilizing same for electrochemical detection of nitro-containing compounds.

What is claimed is: 
     
         1 . An electrochemical cell comprising a sensing electrode, said sensing electrode being a working electrode and comprising a carbon electrode and a functional moiety covalently attached to a surface of said electrode, said functional moiety comprising an electron donating moiety and forms a charge-transfer complex with a nitro-containing compound,
 the electrochemical cell being such that upon contacting said nitro-containing compound with said sensing electrode and applying potential to said sensing electrode, a change in an electrochemical parameter as a result of electrochemical reduction of one or more nitro groups of said nitro-containing compound is effected.   
     
     
         2 . The electrochemical cell of  claim 1 , wherein said carbon electrode is a carbon fiber microelectrode. 
     
     
         3 . The electrochemical cell of  claim 1 , wherein said carbon electrode is a carbon paper microelectrode. 
     
     
         4 . The electrochemical cell of  claim 1 , wherein said carbon electrode is gas-permeable. 
     
     
         5 . The electrochemical cell of  claim 1 , wherein said carbon electrode is a surface-modified carbon electrode featuring a plurality of surface reactive groups. 
     
     
         6 . The electrochemical cell of  claim 1 , wherein said electron donating moiety is a C 1-10  alkyl substituted by an electron donating group. 
     
     
         7 . The electrochemical cell of  claim 6 , wherein said electron donating group is amine. 
     
     
         8 . The electrochemical cell of  claim 6 , wherein said alkyl is substituted by a —NR′R″ group, wherein R′ and R″ are each independently selected from hydrogen, alkyl and cycloalkyl. 
     
     
         9 . The electrochemical cell of  claim 1 , wherein said functional moiety comprises a silyl substituted by an aminoalkyl, said alkyl being 1-10 carbon atoms in length. 
     
     
         10 . The electrochemical cell of  claim 1 , further comprising an electrolyte solution in contact with said sensing electrode. 
     
     
         11 . The electrochemical cell of  claim 10 , wherein said electrolyte features a pH lower than 8, or lower than 7. 
     
     
         12 . A sensing system comprising the electrochemical cell according to  claim 1 . 
     
     
         13 . The sensing system of  claim 12 , further comprising a power source electrically connected to said sensing electrode. 
     
     
         14 . The sensing system of  claim 12 , further comprising a device for measuring an electrochemical parameter of said sensing electrode. 
     
     
         15 . A method of detecting a nitro-containing compound in a sample, the method comprising:
 introducing the sample to the electrochemical cell according to  claim 1 ;   applying potential to said sensing electrode; and   measuring an electrochemical parameter of said sensing electrode, wherein a presence and/or level of said parameter is indicative of a presence and/or level of the nitro-containing compound in the sample.   
     
     
         16 . The method of  claim 15 , wherein said electrochemical parameter comprises an electrical current generated at said sensing electrode, wherein a presence and/or level of said electrical current is indicative of a presence and/or level of the nitro-containing compound. 
     
     
         17 . The method of  claim 15 , wherein said nitro-containing compound is a nitro-containing explosive. 
     
     
         18 . A process of preparing a sensing electrode which comprises comprising a carbon electrode and a functional moiety covalently attached to a surface of said electrode, said functional moiety comprising an electron donating moiety and forms a charge-transfer complex with a nitro-containing compound, the process comprising:
 coupling to a carbon electrode featuring a plurality of a first reactive group on at least a portion of its surface, a compound featuring said functional moiety and a second reactive group that forms a covalent bond with said first reactive group,   thereby preparing the electrode.   
     
     
         19 . The process of  claim 18 , further comprising, prior to said coupling, generating said first reactive group on said at least a portion of said surface of the carbon electrode. 
     
     
         20 . The process of  claim 19 , wherein said generating said reactive groups comprises subjecting the carbon electrode to oxygen plasma treatment. 
     
     
         21 . The process of  claim 18 , wherein said electron donating moiety is a C 1-10  alkyl substituted by an electron donating group. 
     
     
         22 . The process of  claim 21 , wherein said electron donating group is amine. 
     
     
         23 . The process of  claim 18 , wherein said functional moiety comprises a silyl substituted by an aminoalkyl, said alkyl being 1-10 carbon atoms in length.