Electrochemical detection of the explosive, hexamethylene triperoxide diamine (HMTD)

Visual colorimetric detection of triacetone triperoxide based on a Fe(II)-promoted thermal decomposition process

Triacetone triperoxide (TATP) explosives, a popular choice for terrorists, have been used in many violent terrorist attacks all over the world. However, simple, rapid, and on-site detection methods of TATP are still lacking. Herein, we present a visual colorimetric method for on-site and rapid detection of TATP based on a Fe(II)-promoted thermal decomposition process of TATP. We discovered that TATP can be decomposed into H₂O₂ under heating conditions, and it reacts with Fe²⁺ to produce hydroxyl radicals (˙OH) and Fe³⁺via the Fenton reaction. The resulting ˙OH and Fe³⁺ further oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to a yellow oxidized product (oxTMB). These reaction processes remarkably promote the chemical equilibrium shift and decrease the activation energy. Using the TATP-Fe²⁺-TMB ternary chromogenic system, the present colorimetric assay for TATP shows a dynamic range of 0.5-30 μM with a low detection limit of 0.12 μM. Additionally, common substances (e.g., inorganic salts, small organic substances, and polymers) do not interfere with TATP detection. This assay can be used for analyzing TATP in real water and camouflage samples. Furthermore, a test-paper-based method was also successfully developed for visual, rapid and on-site detection of TATP.

Differentiation among peroxide explosives with an optoelectronic nose

Forensic identification of batches of homemade explosives (HME) poses a difficult analytical challenge. Differentiation among peroxide explosives is reported herein using a colorimetric sensor array and handheld scanner with a field-appropriate sampling protocol. Clear discrimination was demonstrated among twelve peroxide samples prepared from different reagents, with a classification accuracy >98%.

Electrochemical Reduction and Detection of Nitrobenzene Based on Porphyrin Composite-modified Glassy Carbon Electrode

An electrocatalytic platform and electrochemical sensor for nitrobenzene using tetra(4-methoxyphenyl) porphyrin-functionalized N-doped ordered mesoporous carbon (TMPP/N-OMC) as sensitive material is reported. Glassy carbon electrodes modified with TMPP/N-OMC were characterized by scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The electrode shows high electrocatalytic activity towards the reduction of nitrobenzene in sodium chloride solution (pH 7.00). Electrocatalytic reduction currents of nitrobenzene were found to be linearly related to concentration over the range 0.528 to 132.00 μM with a correlation coefficient of 0.9971 using a differential pulse voltammogram method. The detection limits were determined as 0.2162 μM at a signal-to-noise ratio of 3. The results show TMPP/N-OMC-modified glassy carbon electrodes open new opportunities for fast, simple, and sensitive field analysis of nitrobenzene.

Detection of Impurities in Organic Peroxide Explosives from Precursor Chemicals

Previous analyses of organic peroxide explosives have focussed on identification of the explosive itself, and were performed using explosive samples synthesized from laboratory-grade precursors. In this work, analytical studies of precursors obtained from retail outlets identified compounds that could be carried over into the explosives as impurities during synthesis. Forensic and intelligence information may be gained by the identification of possible precursor impurities in explosive samples. This hypothesis was tested using triacetone triperoxide and hexamethylene triperoxide diamine prepared from domestically available off-the-shelf precursors. Gas chromatography–mass spectrometry analysis showed that compounds originating from such precursors could be detected in the organic peroxide samples at different stages in their purification. Furthermore, some compounds could also be detected in the residues of samples that had been subjected to thermal initiation.

Current trends in the detection of peroxide-based explosives

The increased use of peroxide-based explosives (PBEs) in criminal and terrorist activity has created a demand for continued innovation in the detection of these agents. This review provides an update to a previous 2006 review on the detection of PBEs, with a focus in this report on luminescence and fluorescence methods, infrared and Raman spectroscopy, mass spectrometry, and electrochemical techniques. Newer developments in gas chromatography and high performance liquid chromatography methods are also discussed. One recent trend that is discussed is an emphasis on field measurements through the use of portable instruments or portable assay formats. An increase in the use of infrared spectroscopy and mass spectrometry for PBE analysis is also noted. The analysis of triacetone triperoxide has been the focus in the development of many of these methods, although hexamethylene triperoxide diamine has received increased attention in PBE detection during the last few years.