Structural characteristics of modified activated carbons and adsorption of explosives

Several series of activated carbons prepared by catalytic and noncatalytic gasification and subsequent deposition of pyrocarbon by pyrolysis of methylene chloride or n-amyl alcohol were studied by FTIR, chromatography, and adsorption methods using nitrogen and probe organics (explosives). The relationships between the textural characteristics of carbon samples and the recovery rates (eta) of explosives on solid-phase extraction (SPE) using different solvents for their elution after adsorption were analyzed using experimental and quantum chemical calculation results. The eta values for nitrate esters, cyclic nitroamines, and nitroaromatics only partially correlate with different adsorbent parameters (characterizing microporosity, mesoporosity, pore size distributions, etc.), polarity of eluting solvents, or characteristics of probe molecules, since there are many factors strongly affecting the recovery rates. Some of the synthesized carbons provide higher eta values than those for such commercial adsorbents as Hypercarb and Envicarb.     

Calculation of the composition of detonation products and optimization of dynamic characteristics for mixed explosives

A mathematical model describing the composition of products and dynamic characteristics for the detonation of a multicomponent mixture of condensed explosives was proposed. The model consists of a system of equations with respect to a possible composition and temperature with allowance for the laws of conservation, partial conditions of detailed equilibrium, and semiempirical functional dependence of the energy-release coefficient. The numerical solution of these equations makes it possible to predict a relative impulse, rate, and pressure of detonation of individual explosives and their mixtures and to solve the problem of optimization of the detonation characteristics by composition. The application of the model for the calculation of optimum compositions for standard explosives with the empirical formula C _a H _b N _c O _d F _e was considered.     

Thermochemistry of explosives

The kinetics constants for the decomposition reaction of an explosive can be used to calculate the lowest temperature (critical temperature, T_m) at which any specific size and shape of explosive can self heat to explosion; however, the accuracy of the calculation is in doubt without an independent experimental determination of a critical temperature for a known size and shape of the explosive. A method is presented for the experimental determination of critical temperatures on a routine basis, and it is shown that agreement between calculated and experimental values is excellent for most common explosives.     

Femtosecond laser photoionization time-of-flight mass spectrometry of nitro-aromatic explosives and explosives related compounds

The ultrafast laser-induced photoionization and photodissociation processes of the nitroaromatic containing explosive and explosive related compounds (ERCs) nitrobenzene (NB), 1,3-dinitrobenzene (DNB), m-nitrotoluene (MNT), 2,4-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT) have been investigated at three laser wavelengths and power densities using a time-of-flight mass spectrometer. Examination of the mass spectra of these compounds reveals the enhanced formation of the molecular ion [M⁺] when ultraviolet (332 nm) and visible (495 nm) light is used relative to infrared (795 nm) radiation. In addition, at 795 nm and a power density of 3. 5 × 10¹⁴ W/cm², the presence of a competition between multiphoton ionization (MPI) and Coulomb explosion (CE) channels is revealed by peak shape analysis, and is thought to be operative under these conditions for all of the molecules investigated.     

Detection agents for explosives

DSC measurements have been used to investigate the thermal stability of each of four specific detection agents, prescribed by the International Civil Aviation Organization for incorporation into explosives at the point of manufacture. Additionally, the compatibility of these agents with a number of commercial explosives has been assessed. DSC results for a complete study of mixtures of the agents with the explosive, tetryl are specifically described. The thermograms are compared with those of the pure agents and tetryl, the thermal decomposition of which has been previously characterized.     

Portable Raman explosives detection

Recent advances in portable Raman instruments have dramatically increased their application to emergency response and forensics, as well as homeland defense. This paper reviews the relevant attributes and disadvantages of portable Raman spectroscopy, both essentially and instrumentally, to the task of explosives detection in the field.     

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.     

Recent methods for the determination of peroxide-based explosives

In the last few years, the need to determine peroxide-based explosives in solid samples and air samples has resulted in the development of a series of new analytical methods for triacetonetriperoxide (TATP, acetone peroxide) and hexamethylenetriperoxidediamine (HMTD). In this review, after a short introduction describing the state of the art in the field, these new analytical methods are critically discussed. Particular emphasis is placed on spectroscopic and mass spectrometric methods as well as on chromatographic techniques with selective detection schemes. The potential of these methods to analyse unknown solid samples that might contain one or more of the explosives and to analyse peroxide-based explosives in air is evaluated.     

Detonability of aqueous suspensions of explosives

The detonability of aqueous suspensions of solid explosives (pentaerythritol tetranitrate, cyclotrimethylenetrinitramine, cyclotetramethylenetetranitramine) was used as a basis for evaluating the explosion safety of these substances in production and transportation. The dependence of the critical detonation parameters of the suspensions on the content and dispersity of the explosives was determined. A new common method for calculating the critical detonation diameters of suspensions of crystalline explosives in organic media and in water was developed. A novel procedure for preparing uniform sedimentation-resistant aqueous suspensions of crystalline explosives was suggested and developed.     

毛细管电泳在火炸药研究中的应用

近年来,毛细管电泳以其高效、快速、微量的特点,在火炸药分析领域被广泛应用并迅速发展。本文从毛细管区带电泳、胶束电动毛细管色谱、毛细管电色谱、芯片毛细管电泳、微乳毛细管电动色谱这五种毛细管电泳的模式出发,结合本实验室的最新研究进展,综述毛细管电泳在火炸药研究中的应用。     

A method for detecting explosives

Bombs concealed in luggage have threatened human life and property throughout the world's traffic. The plastic explosives could not be checked by the X-ray detecting device. A method has been tested in the present work for non-destructive detection of explosives. A neutron generator and relevant apparatus have been used as a tool to find explosives, regardless of the bomb's shape and the packing materials. It seems that this method is a promising one because of the strong transmission ability of both the incident and output specific radiations and low background.     

Chemical ionisation mass spectra of explosives

The chemical ionisation mass spectra of a number of representative explosives have been obtained using hydrogen as reagent gas. Fragmentation modes of the protonated molecular ions tend to be simple although some rearrangements have been noted. Loss of a radical from an even electron parent ion has been observed. The use of ‘ghost spectra’ for confirmation of the molecular weight of the sample is stressed: these consist of ions of low abundance resulting from reactions between sample ions and sample molecules. Labelling studies were carried out using deuterium as reagent gas.     

Vibrational spectroscopy standoff detection of explosives

Standoff infrared and Raman spectroscopy (SIRS and SRS) detection systems were designed from commercial instrumentation and successfully tested in remote detection of high explosives (HE). The SIRS system was configured by coupling a Fourier-transform infrared interferometer to a gold mirror and detector. The SRS instrument was built by fiber coupling a spectrograph to a reflective telescope. HE samples were detected on stainless steel surfaces as thin films (2–30 μg/cm²) for SIRS experiments and as particles (3–85 mg) for SRS measurements. Nitroaromatic HEs: TNT, DNT, RDX, C4, and Semtex-H and TATP cyclic peroxide homemade explosive were used as targets. For the SIRS experiments, samples were placed at increasing distances and an infrared beam was reflected from the stainless steel surfaces coated with the target chemicals at an angle of ∼180° from surface normal. Stainless steel plates containing TNT and RDX were first characterized for coverage distribution and surface concentration by reflection–absorption infrared spectroscopy. Targets were then placed at the standoff distance and SIRS spectra were collected in active reflectance mode. Limits of detection (LOD) were determined for all distances measured for the target HE. LOD values of 18 and 20 μg/cm² were obtained for TNT and RDX, respectively, for the SIR longest standoff distance measured. For SRS experiments, as low as 3 mg of TNT and RDX were detected at 7 m source–target distance employing 488 and 514.5 nm excitation wavelengths. The first detection and quantification study of the important formulation C4 is reported. Detection limits as function of laser powers and acquisition times and at a standoff distance of 7 m were obtained.     

A field test for the detection of peroxide-based explosives

A rapid and simple field test for the detection of triacetone-triperoxide (TATP) and hexamethylenetriperoxidediamine (HMTD), two explosives which find significant illegal use, has been developed. Unknown samples are first treated with a catalase solution to remove hydrogen peroxide traces, in order to provide selectivity towards peroxide-based bleaching agents which are contained in commercial laundry detergents. Subsequently, the peroxide-based explosives are decomposed via UV irradiation, thus yielding hydrogen peroxide, which is determined by the horseradish peroxidase (POD) catalysed formation of the green radical cation of 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS). The limits of detection for this method are 8 x 10(-6) mol dm(-3) for TATP and 8 x 10(-7) mol dm(-3) for HMTD, respectively. As an option, p-hydroxyphenylacetic acid (pHPAA) may be used as peroxidase substrate, resulting in lower limits of detection (8 x 10(-7) mol dm(-3) for TATP and HMTD). The complete method uses a mobile setup to be applied under field conditions.     

Progress in methods for the identification of explosives in Russia

The progress in analytical methods for the determination of explosive done by Russian scientists is reviewed: gas analytical; nuclear physical, including neutron activation analysis; nuclear quadruple resonance (NQR); and optical spectroscopy.