2. PHYSICO-CHEMICAL STUDIES OF EXPLOSIVE SUBSTANCES

(conducted by experts Bogdanov V.M. and Stovbur K.N.)

In order to detect trace amounts of high explosives (HE) and components of mixed explosives, the submitted objects were examined using the methods of optical microscopy, ion chromatography (IC), high-performance thin-layer chromatography (HPTLC), chromatography-mass spectrometry (GC-MS), and scanning electron microscopy with X-ray spectral microanalysis (SEM-EDX) in the following sequence.

Initially, to detect microparticles of components of mixed explosives and pyrotechnic compositions (fine powders of magnesium, aluminum, ammonium nitrate, etc.) and gunpowder particles, all objects were examined visually using a Leica MZ12 microscope (Germany) at various magnifications and lighting conditions.

As a result of the study on the objects listed in items 3.1, 4.1 – 4.6, 5.1 (here and hereafter – the items correspond to those given in the "External Examination" section), silver-gray particles with a characteristic metallic luster were found. These particles resemble metallic aluminum particles in appearance. Metallic aluminum can be a component of mixed explosives and pyrotechnic compositions.

To detect trace amounts of high explosives and components of mixed explosives from the presented objects, methanol swabs were taken. The swabs were filtered through "white ribbon" ashless paper filters and, after evaporation in a helium stream to a volume of 1 ml, were divided in half. One part, intended for study by HPTLC and GC-MS methods, was evaporated to a volume of 0.2 - 0.3 ml; the other, intended for analysis by the IC method, was dried until the solvent was completely removed and then filled with 1 ml of bidistilled water for each swab. The remaining paper filters were dried and preserved for further studies.

The HPTLC study was conducted using a set of chromatographic equipment from the "Camag" company (Switzerland) under the following conditions:
* "HPTLC Silica gel 60 F 254" plate from "Merck" (Germany);
* applied sample volume - 40 μl;
* eluent - benzene;
* eluent rise height from the start line - 50 mm;
* control samples - acetone solution of the most well-known high explosives (TNT, RDX, HMX, PETN, nitroglycerin, tetryl, and picric acid), chloromethylene extracts of various brands of smokeless powders.