Trinitrotoluene detection

Guo CX, Lu ZS, Lei Y et al (2010) Ionic liquid-graphene composite for ultratrace explosive trinitrotoluene detection. Electrochem Commun 12 1237-1240... 

Fast concentration and sample injection are considered with the use of a theory of vibrational relaxation. A possibility to reduce a detection limit for trinitrotoluene to 10 g/cnf in less than 1 min is shown. Such a detection limit can by obtained using selective ionization combined with ion drift spectrometry. The time of detection in this case is 1- 3 s. A detection technique based on fluorescent reinforcing polymers, when the target molecules strongly quench fluorescence, holds much promise for developing fast detectors. 

An important demonstrated application of this artificial nose system is the high-speed detection of low levels of explosives and explosive-like vapors. Several sensors, based on Nile Red attached to silica microspheres, show high sensitivity to nitroaromatic compounds (NAC) within a mixture12. Different fluorescence response profiles were observed for several NAC s, such as 1,3,5-trinitrotoluene (TNT) and 1,3-dinitrobenzene (DNB), despite their similar structures. These responses were monitored at low concentrations of the NAC vapors (ca. 5 ppb) and at short vapor exposure... 

K. Matsumoto, A. Torimaru, S. Ishitobi, T. Sakai, H. Ishikawa, K. Toko, N. Miura, and T. Imato, Preparation and characterization of a polyclonal antibody from rabbit for detection of trinitrotoluene by a surface plasmon resonance biosensor. Talanta 68, 305-311 (2005). 

The choice of solid-phase microextraction sorbent phase was shown to be important especially for the amino metabolities of trinitrotoluene and RDX, which were extracted better on polar phases. Although equilibration times were quite lengthy, on the order of 30 min or greater, a sampling time of only 10 min was shown to be sufficient for achieving low part-per-billion (ppb) to part-per-trillion (ppt) detection limits for trinitrotoluene and the amino metabolities in real seawater samples. Solid-phase microextraction was ideal for rapid screening of explosives in seawater samples. 

Electron-transfer-induced FQ is the most practical and efficient mechanism of signal transduction for the detection of explosives. This is because explosives, especially 2,4,6-trinitrotoluene (TNT), are often highly electron-deficient molecules that readily accept electrons from excited fluorophores. In addition, explosive devices that contain TNT also usually contain a synthetic by-product, 2,4-dinitrotoluene (DNT), which is also highly electron deficient. A basic frontier molecular orbital-based mechanism for electron transfer FQ is illustrated in Figure 3. 

Before anything else can be said about IEs, some rudimentary chemistry is needed. From a cookbook perspective, all explosives (be they military, commercial, or improvised) require the same chemical building blocks, which consist of a fuel and an oxidizer. Some explosives have the fuel and oxidizer as part of the same molecule, such as trinitrotoluene (TNT), and some explosives are comprised of mixtures of separate fuels and oxidizers, such as ammonium nitrate-fuel oil (ANFO). The oxidizer employed by the vast majority of explosives tends to be the NO2 (nitro) group. It is so predominant as an explosive ingredient that the primary focus of detection methods traditionally has been to look for nitro-derived properties. IEs tend to utilize a more diverse range of oxidizers. Table 3.1 gives a list of the numerous oxidizer possibilities. 

Hilmi and Luong [25] employed a gold working electrode, formed by electroless deposition onto the chip capillary outlet, for highly sensitive amperometric detection of nitroaromatic explosives [with a detection limit of 24 ppb trinitrotoluene (TNT)]. Analysis of a mixture of four explosives (TNT, 2,4-DNT,... 

Bromberg, A. and R. A. Mathies. Multichannel homogeneous immunoassay for detection of 2,4,6-trinitrotoluene (TNT) using a microfabricated capillary array electrophoresis chip. Electrophoresis 25, 1895-1900 (2004). 

Buckley J.B. French, The Real Time Detection of Trinitrotoluene in Ambient Air Using TAG A System , UTIAS Tech, 213, 7 (1977)... 

In another approach, a fluorescent conjugated polymer was used as the material for the preparation of a chemosensor to detect 2,4,6-trinitrotoluene (TNT) and its related nitroaromatic compounds. To this end, microparticles, made of three-dimensionally cross-linked poly(l,4-phenylene vinylene) (PPV) via emulsion polymerization, were synthesized [61]. This material was chosen due to its high fluorescence intensity and sensitivity to changes in its microenvironment. The chemosensor was exposed to vapour containing different amounts of TNT and quenching of the polymer luminescence at 560 nm was observed after excitation at 430 nm. The dependence of the fluorescence signal in response to the analyte was described by a modified Stem-Volmer equation that assumes the existence of two different cavity types. The authors proposed the modified Stem-Volmer equation as follows ... 

Nitrogen-containing explosives [249] and trinitrotoluene [250] have been determined in soil by gas chromatography with thermionic NP detection and reverse-phase high-performance liquid chromatography. Warmont et al. [251] used tunable infrared laser detection to study the pyrolysis products of explosives in soil. 

Abbreviations DNA, deoxyribose nucleic acid ECD, electrochemical detection LIF, laser induced fluorescence LOD, limit of detection PDMS, poly(dimethylsiloxane) PSA, prostate specific antigen TOF-MS, time-of-flight mass spectrometer TNT, 2,4,6-trinitrotoluene. 

Poly(l,l-silole)s, SCPs catenated through the ring silicon atom, can be regarded as a new class of polysilanes. It was found that PL intensities of the toluene solution of a poly(l,l-silole) 24 (Fig. 12) could be quenched by the addition of tiny amounts of 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenol (picric acid), 2,4-dinitrotoluene (DNT), and nitrobenzene, demonstrating that poly(l,l-silole)s are potential chemosensors for explosives.41 TNT could also be detected using the polymer film. In an air stream containing 4 ppb TNT, 8.2% decrease of the PL intensity was found from the film. PL quenching can also be detected when the film contacts a 50 ppb TNT-water solution. 

After patterning antibodies as an array using the PDMS microchannel, TNT (2,4,6-trinitrotoluene) was detected using the heterogeneous immunoassay format... 

BTT and BTN, butane-1,2,4-triol-trinitrate DNT, dinitrotoluene EGDN, ethylene glycol dinitrate HPLC, high-performance liquid chromatography LOD, limits of detection MDQ, minimum detectable quantities NB, nitrobenzene NG, nitroglycerine NN, nitronaphthalene NT, nitrotoluene PETN, pentaerythritol tetranitrate RDX, cyclotrimethylene trinitramine SFE, supercritical fluid extraction SGC, solvating gas chromatography TDM, thermal desorption modulator TNB, trinitrobenzene and TNT, trinitrotoluene. 

Fig. 9. Enzyme electrochemiluminescence (ECL) immunoassay protocol, (a) Trinitrotoluene (TNT) and dini-trophenyl of haptenylated dextran compete for antibody-binding sites, (b) Antibodies attached to dextran bound to streptavidin-coated paramagnetic beads, (c) ECL detection of enzyme-labelled antibodies magnetically concentrated on electrode. Reprinted from Wilson et al. [68], Copyright (2003), with permission...

Fig. 15. (Continued) (c) Differential mobility spectra of 4-mononitrotoluene (4-MNT) in air at different concentrations. Product ions can only be detected in the positive mode, negative product ions cannot be observed, (d) Differential mobility spectra of 2,4,6-trinitrotoluene (TNT) in air at different concentrations. Product ions can only be detected in the negative mode, positive product ions cannot be observed. Source A.A. Cagan, H. Schmidt, G.A. Eiceman, NMSU (unpublished results, 2006).

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