Direct Electrochemical Determination of Peroxide-Type\nExplosives Using Well-Dispersed Multi-Walled Carbon Nanotubes/Polyethyleneimine-Modified\nGlassy Carbon Electrodes

Abstract

The\nsensitive and selective determination of peroxide-based explosives\n(PBEs) in the field/on site is an important analytical challenge.\nMost methods claiming to detect PBEs are indirect, actually detecting\ntheir decomposition product, H₂O₂. Here, we\npresent an electrochemical sensor for direct detection of organic\nperoxide explosives, that is, triacetone triperoxide (TATP) and hexamethylenetriperoxide\ndiamine (HMTD), using well-dispersed multiwalled carbon nanotubes/polyethyleneimine\n(MWCNTs/PEI)-modified glassy carbon (GC) electrode, namely, GC/MWCNTs/PEI\nelectrode. This is the first use of the conductive polyelectrolyte\nPEI as an electrode modifier for pristine PBE sensing. The potential\nrange, scan rate, solvent selection, and supporting electrolyte concentration\nwere optimized for PBEs. As a distinct advantage over other similar\nmethods, our sensor electrode responded to intact TATP solutions in\nneutral medium, meaning that TATP did not interact with acids/bases\nthat would transform it into H₂O₂. Calibration\ncurves were linear in the range of 10–200 mg L^–1 for TATP and 25–200 mg L^–1 for HMTD. Using\ndifferential pulse voltammetry, detection limits of 1.5 mg L^–1 TATP and 3.0 mg L^–1 HMTD were obtained from direct\nelectrochemical reduction in 80/20% (v/v) H₂O–acetone\nsolvent medium. Electroactive camouflage materials such as passenger\nbelongings (e.g., sweetener, detergent, sugar, and paracetamol–caffeine-based\nanalgesic drugs), common ions, and other explosives were shown not\nto interfere with the proposed method. The nonresponsive behavior\nof our electrode to H₂O₂ prevents “false\npositives” from other peroxide materials of everyday use. This\nelectrochemical sensor could also detect other nitro-explosives at\ndifferent potentials and was statistically validated against standard\nGC–MS and spectrophotometric methods.