Taggant

Abstract: We have investigated a series of branched fluorescent sensing compounds with thiophene units in the arms and triphenylamine centers for the detection of nitrated model compounds for 2,4,6-trinitrotoluene (TNT) and the plastic explosives taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB). Stern−Volmer measurements in solution show that the fluorescence is more efficiently quenched by nitroaromatic compounds when compared to a non-nitrated quencher, benzophenone. Simple modification of the structure of the sensing compound was found to result in significant changes to the sensitivity and selectivity toward the nitrated analytes. A key result from time-resolved fluorescent measurements showed that the chromophore−analyte interaction was primarily a collisional process. This process is in contrast to conjugated polymers where static quenching dominates, a difference that could offer a potentially more powerful detection mechanism.

Abstract: Ion mobility spectrometry (IMS) is a rugged, inexpensive, sensitive, field portable technique for the detection of organic compounds. It is widely employed in ports of entry and by the military as a particle detector for explosives and drugs of abuse. Solid phase microextraction (SPME) is an effective extraction technique that has been successfully employed in the field for the pre-concentration of a variety of compounds. Many organic high explosives do not have a high enough vapor pressure for effective vapor sampling. However, these explosives and their commercial explosive mixtures have characteristic volatile components detectable in their headspace. In addition, taggants are added to explosives to aid in detection through headspace sampling. SPME can easily extract these compounds from the headspace for IMS vapor detection. An interface that couples SPME to IMS was constructed and evaluated for the detection of the following detection taggants: 2-nitrotoluene (2-NT), 4-nitrotoluene (4-NT), and 2,3-dimethyl-2,3-dinitrobutane (DMNB). The interface was also evaluated for the following common explosives: smokeless powder (nitrocellulose, NC), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 2,4,6-trinitrotoluene (2,4,6-TNT), hexahydro-1,3,5-trinitro-s-triazine (RDX), and pentaerythritol tetranitrate (PETN). This is the first peer reviewed report of a SPME-IMS system that is shown to extract volatile constituent chemicals and detection taggants in explosives from a headspace for subsequent detection in a simple, rapid, sensitive, and inexpensive manner.

Abstract: A method of tagging and detecting objects is disclosed which comprises the steps of: (a) applying a volatile taggant to the object; and (b) subsequently detecting the presence of the taggant by the absorption, transmittance, reflectance, photon emission or fluorescence of the taggant and therefore a proximity of the tagged object. The present invention therefore provides optical sensing means which do not require physical separation of differing compounds for discrimination thereof.

Abstract: Vapor detection of plastic explosives is difficult because of the low vapor pressures of explosive components (i.e. RDX and PETN) present in the complex elastomeric matrix. To facilitate vapor detection of plastic explosives, detection agents (taggants) with higher vapor pressures can be added to bulk explosives during manufacture. This paper investigates the detection of two of these taggants, ethyleneglycol dinitrate (EGDN) and 2,3-dimethyl-2,3-dinitrobutane (DMNB), using a handheld ion mobility spectrometer. These two taggants were detected both from neat vapor sources as well as from bulk explosives (nitroglycerin (NG)-dynamite and C-4 tagged with DMNB). EGDN was detected from NG-dynamite as EGDN·NO3− at a reduced mobility value of 1.45 cm2 V−1 s−1 with detection limits estimated to be about 10 ppbv. DMNB was identified from tagged C-4 as both negative and positive ions with reduced mobility values of 1.33 cm2 V−1 s−1 for DMNB·NO2− and 1.44 cm2 V−1s−1 for DMNB·NH4+. Positive ions for cyclohexanone were also apparent in the spectra from tagged C-4 producing three additional peaks. © 2001 John Wiley & Sons, Inc. Field Analyt Chem Technol 5: 215–221, 2001