Direct Electrochemical Determination of Peroxide-Type Explosives Using Well-Dispersed Multi-Walled Carbon Nanotubes/Polyethyleneimine-Modified Glassy Carbon Electrodes

Abstract

The sensitive and selective determination of peroxide-based explosives (PBEs) in the field/on site is an important analytical challenge. Most methods claiming to detect PBEs are indirect, actually detecting their decomposition product, H2O2. Here, we present an electrochemical sensor for direct detection of organic peroxide explosives, that is, triacetone triperoxide (TATP) and hexamethylenetriperoxide diamine (HMTD), using well-dispersed multiwalled carbon nanotubes/polyethyleneimine (MWCNTs/PEI)-modified glassy carbon (GC) electrode, namely, GC/MWCNTs/PEI electrode. This is the first use of the conductive polyelectrolyte PEI as an electrode modifier for pristine PBE sensing. The potential range, scan rate, solvent selection, and supporting electrolyte concentration were optimized for PBEs. As a distinct advantage over other similar methods, our sensor electrode responded to intact TATP solutions in neutral medium, meaning that TATP did not interact with acids/bases that would transform it into H2O2. Calibration curves were linear in the range of 10-200 mg L-1 for TATP and 25-200 mg L-1 for HMTD. Using differential pulse voltammetry, detection limits of 1.5 mg L-1 TATP and 3.0 mg L-1 HMTD were obtained from direct electrochemical reduction in 80/20% (v/v) H2O-acetone solvent medium. Electroactive camouflage materials such as passenger belongings (e.g., sweetener, detergent, sugar, and paracetamol-caffeine-based analgesic drugs), common ions, and other explosives were shown not to interfere with the proposed method. The nonresponsive behavior of our electrode to H2O2 prevents "false positives" from other peroxide materials of everyday use. This electrochemical sensor could also detect other nitro-explosives at different potentials and was statistically validated against standard GC-MS and spectrophotometric methods.