Sensitive Determination of Hexamethylene Triperoxide Diamine Explosives, Using Electrogenerated Chemiluminescence Enhanced by Silver Nitrate

Abstract

Sensitive detection and quantification of hexamethylene triperoxide diamine (HMTD), which is one of commonly used explosives by terrorists, was presented on the basis of electrogenerated chemiluminescence (ECL) technology coupled with silver nitrate (AgNO3) enhancement in acetonitrile at a platinum electrode. Upon anodic potential scanning, HMTD irreversibly oxidized at approximately 1.70 V vs Ag/Ag+ (10 mM) at a scan rate of 50 mV/s, and the ECL profile was coincident with the oxidation potential of HMTD in the presence of ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) luminophore species, which showed a half-wave potential of 0.96 V vs Ag/Ag+. The addition of small amounts of AgNO3 (0.50-7.0 mM) into the HMTD/Ru(bpy)3(2+) system resulted in significant enhancement in HMTD ECL production (up to 27 times). This enhancement was determined to be largely associated with NO3(-) and was linearly proportional to the concentrations of NO3(-) and Ag+ in solution. Homogeneous chemical oxidations of HMTD by electrogenerated NO3* and Ag(II) species proximity to the electrode were proposed to be responsible for the ECL enhancement. On the basis of cyclic voltammetry (CV) and CV digital simulations, standard potential values of 1.79 V vs Ag/Ag+ (or 1.98 V vs NHE) and 1.82 V vs Ag/Ag+ (or 2.01 V vs NHE) were estimated for Ag(II)/Ag(I) and NO3*/NO3(-) couples, respectively. A detection limit of 50 microM of HMTD was achieved with the current technique, which was 10 times more sensitive than that reported previously, which was based on a high-performance liquid chromatography/Fourier transform infrared (HPLC/FT-IR) detection method.