Electrochemical Method And Sensor For The Detection Of Traces Of Explosives

Abstract

A system for highly sensitive electrochemical detection of trace nitro-aromatic compounds in air, uses a carbon or carbon/gold working electrode with a surface that is modified to increase the electron transfer kinetics of nitro-aromatic compounds, Chemical modifiers of the working electrode surface include amino-aromatic compounds such as aniline and its derivatives The detection method involves dissolving trace nitro-aromatic compounds in an electrolyte including aprotonic solvents, or dipolar solvents, in the electrochemical cell including a working electrode, a reference electrode and an auxiliary electrode. Voltage is varied across the working electrode and the reference electrode, and an electrical current is measured between the working electrode aid the auxiliary electrode. The measured electrical peak current is a sensitive indication of the concentration of the trace compounds. This invention is appropriate for portable, field-testing of trace explosive compounds in air.

1 . An electrochemical method for assaying trace nitro-aromatic compounds, the method comprising the steps of: 
 (a) providing an electrolyte including a mixed solvent of water and an organic solvent selected from the group consisting of aprotonic solvents and organic dipolar solvents;    (b) immersing a working electrode in said electrolyte, said working electrode having a surface including at least one element selected from the group of carbon and gold;    (c) applying a varying potential to said working electrode; and    (d) measuring an electrical current consequent to said varying potential, thereby providing measurement results indicative of a concentration of the nitro-aromatic compound.    
   
   
       2 . The electrochemical method, according to  claim 1 , further comprising the step of: 
 (e) regenerating said working electrode by applying a negative potential to said working electrode.    
   
   
       3 . The electrochemical method, according to  claim 1 , further comprising the step of: 
 (e) dissolving the nitro-aromatic compounds in said electrolyte by bubbling air containing the nitro-aromatic compounds through said electrolyte.    
   
   
       4 . The electrochemical method, according to  claim 1 , further comprising the step of: 
 (e) measuring a background electrical current, while said applying a varying potential, thereby obtaining background current results.    
   
   
       5 . The electrochemical method, accord to  claim 4 , further comprising the step of: 
 (f) subtracting said background current results from said measurement results, thereby obtaining calibrated measurement results.    
   
   
       6 . The electrochemical method, according to  claim 1 , wherein organic solvent is selected from the group consisting of dimethylformamide, acetonitrile, propylene carbonate.  
   
   
       7 . The electrochemical method, according to  claim 6 , wherein said organic solvent is selected from the group consisting of ethanol, propanol, ethylene-glycol, and propylene-glycol.  
   
   
       8 . The electrochemical method, according to  claim 1 , wherein said electrolyte has a pH greater than 7.  
   
   
       9 . The electrochemical method, according to  claim 1 , further comprising the step of, prior to said immersing: 
 (e) preconditioning said working electrode by treatment thereof with a monomeric amino-aromatic compound dissolved in an organic polar solvent.    
   
   
       10 . The electrochemical method, according to  claim 9 , wherein said preconditioning includes modifying a surface of said working electrode with a chemical selected from the group consisting of amino-aromatic compounds, alkyl-aniline compounds, halide derivatives of alkyl aniline compounds and hydroxyl-aniline compounds.  
   
   
       11 . An electrochemical cell comprising the electrolyte and the working electrode for performing the method steps of  claim 1 .  
   
   
       12 . An electrochemical method of assaying nitro-aromatic compounds in air, comprising the steps of: 
 (a) providing an electrolyte including a mixed solvent of water and an organic solvent selected from the group consisting of aprotonic solvents and organic dipolar solvents;    (b) immersing a working electrode in said electrolyte, said working electrode having a surface pre-treated thereof with a monomeric amino-aromatic compound dissolved in an organic polar solvent;    (c) applying a varying potential to said working electrode; (d) measuring an electrical current consequent to said varying potential, thereby providing measurement results indicative of a concentration of the nitro-aromatic compound.    
   
   
       13 . An electrochemical cell comprising the electrolyte and the working electrode for performing the method steps of  claim 12.