Electrochemical determination of nitroaromatic explosives using glassy carbon/multi walled carbon nanotube/polyethyleneimine electrode coated with gold nanoparticles.

The on site/in field detection of explosives has become a rising priority for homeland security and counter-terrorism measures. This work presents the sensitive detection of nitroaromatic explosives using glassy carbon/multi-walled carbon nanotubes/polyethyleneimine (GC/MWCNTs/PEI) electrode coated with gold nanoparticles (AuNPs). MWCNTs and PEI could be well dispersed in ethanol/water solution, giving rise to a thin and homogeneous film on GCE. The GC/MWCNTs/PEI electrode was electrochemically modified with AuNPs and used for the differential pulse voltammetric (DPV) detection of nitroaromatics. The enhanced detection sensitivities were achieved through π-π and charge-transfer (CT) interactions between the electron-deficient nitroaromatic explosives and donor amine groups in PEI to which gold nanoparticles were linked, providing increased analyte affinity toward the modified GCE. Calibration curves of current intensity versus concentration were linear in the range of 0.05-8 mg L for TNT, 0.2-4 mg L for 2,4-dinitrotoluene (DNT), 1-20 mg L for 2,4-dinitrophenol (2,4-DNP), 0.25-10 mg L for picric acid (PA), and 0.05-4 mg L for 2,4,6-trinitrophenyl-N-methylnitramine (tetryl) with detection limits (LOD) of 15 μg L, 45 μg L, 135 μg L, 30 μg L, and 12 μg L, respectively. The proposed method was successfully applied to the analysis of nitroaromatics in synthetic explosive mixtures and military composite explosives (comp B and octol). The electrochemical method was not affected by possible interferents of electroactive camouflage materials and common soil ions. Method validation was performed against the reference LC-MS method on TNT and PA-contaminated clay soil samples separately.