Development of chemical and analytical instrumentation for detecting traces of explosives

A brief review of the development of the chemical and physical foundations of portable analytical instrumentation for detecting traces of explosives is given. Elementary processes in sampling methods are considered, including gas-chromatographic separation of detectable substances, ionization detection, express vapor concentration, remote vortex sampling of vapor from the surface of controlled objects. Multicapillary separation columns (MCCs) containing 1000 capillaries with a diameter of 40 pm were created for the first time for gas chromatographic separation of vapors of detectable substances. Rapid mass transfer in small-diameter capillaries provides high separation efficiency at small column lengths, which reduces the analysis time to 1020 s. Also, it provides a decrease in the separation temperature by about 50 ... 70 ° and the possibility of an isothermal separation mode, which sharply reduces the power consumption of portable devices. New methods of ionization detection of substances have been invented: ion mobility increment spectrometry (IMIS) and ionization detection of tunable selectivity (IDTS). IMIS provides highly sensitive detection of trinitrotoluene (TNT) vapor concentrations up to 10-14 g/cm3 without the use of chromatography. The use of UV laser ionization provides low detection thresholds for vapors of low-volatile explosives: RDX - 5,9 x 10-16 g/cm3, pentaerythritol tetranitrate 9,8 x 10-15 g/cm3. IDTS ensures the operation of a gas chromatographic multicapillary detector of explosive vapors with atmospheric air as a carrier gas, which is convenient when working in the field conditions. The air is purified by a miniature filter built into the detector. The use of a selective IMIS detector in a gas chromatographic detector provides a lowering of the threshold for detecting the concentration of TNT vapors to 10-16 g/cm3. Such a threshold sensitivity for TNT is two orders of magnitude better than that existing in the practice of antiterrorist control. It is shown that such a threshold sensitivity sharply reduces the time of detection of 200 g of TNT in baggage from the moment of putting it in baggage: from several days to 5 minutes. As a result, it was noted that today in the practice of anti-terrorist control portable devices with a detection threshold of explosive vapor concentration of 10-14 g/cm3 are used, in scientific research the thresholds reach 10-16 g/cm3. Sampling technologies are used exclusively. On the surface of controlled objects, there may be micro-quantities of explosives with a surface density of hundreds of ng/cm2. For modern detectors, the characteristic threshold sensitivity by mass in a sample, for example, by TNT, is 10100 pg; therefore, contact sampling of microparticles from the surface of objects began to be used, which increases the efficiency of trace detection, but reduces the speed of control. In order to increase the speed of effective vapor control, devices with a threshold of 10-16 g/cm3 are needed; research and work is being carried out in this direction. the author expresses his sincere gratitude to I.I. Zasypkina for help in the preparation of the article. The author declares no conflicts of interests.

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