Rapid voltammetric determination of nitroaromatic explosives at electrochemically activated carbon-fibre electrodes

The electrochemical behaviour of some nitroaromatic explosives ( 2,4,6- trinitrotoluene, TNT; 2,6dinitrotoluene, 2,6-DNT; 2-nitrotoluene, 2-NT; 2-amino-4,6- dinitrotoluene, 2- A- 4,6- DNT; 3,5- dinitroaniline, 3,5-DNA; and nitrobenzene, NB) at electrochemically activated carbon-fibre microelectrodes is reported. Electrochemical activation of such electrode material by repeated square-wave ( SW) voltammetric scans between 0.0 and + 2.6 V versus Ag/AgCl, produced a dramatic increase in the cathodic response from these compounds. This is attributed to the increase of the carbon-fibre surface area, because of its fracture, and the appearance of deep fissures along the main fibre axis into which the nitroaromatic compounds penetrate. Based on the important contribution of adsorption and/ or thin layer electrolysis to the total voltammetric response, a SW voltammetric method for rapid detection of nitroaromatic explosives was developed. No interference was found from compounds such as hydrazine, phenolic compounds, carbamates, triazines or surfactants. The limits of detection obtained are approximately 0.03 mu g mL(-1) for all the nitroaromatic compounds tested. The method was applied for the determination of TNT in water and soil spiked samples; recoveries were higher than 95% in all cases.