Analysis of Samples

To answer questions 3 and 4 of the decree, the expert selected the most informative samples from among those presented, namely:
* Fragments (items 1, 2, 5, 8, here and hereafter items from the "External Examination")
* Swabs (item 14)
* Soil samples from the scene (items 19 — 24)

The studies were conducted using optical microscopy, high-performance thin-layer chromatography (HPTLC), ion chromatography (IC), chromatography-mass spectrometry (GC-MS), and X-ray spectral microanalysis (RSMA) in the following sequence.

Initial Visual Examination

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

As a result of the study, no microparticles or particles resembling HE, gunpowder, pyrotechnic compositions, or their individual components were found.

Swab Preparation and Analysis

Then, methanol and acetone swabs were taken from the objects. The swabs were filtered through ashless "white ribbon" 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 filled with 1 ml of bidistilled water for each swab.

The remaining filters were dried and saved for further research.

To detect trace amounts of high explosives and organic components of smokeless powders (diphenylamine and centralites), acetone and methanol swabs were studied using HPTLC and GC-MS methods.

HPTLC Study

The HPTLC study was conducted using a complex of chromatographic equipment from Camag (Switzerland) under the following conditions:
* HPTLC Silica gel 60 F 254 plate from Merck (Germany)
* Sample application volume — 40 μl
* Eluent — benzene
* Eluent rise height from the start line — 50 mm
* Control samples — an acetone solution of the most well-known high explosives (TNT, hexogen, octogen, PETN, nitroglycerin, tetryl, and picric acid), chloromethylene extracts of various brands of smokeless powders.

The presence of HE and smokeless powder components was established by the correspondence of the relative mobility values of the substance spots on the chromatograms of the studied and control solutions, as well as by the reaction to the effect of developing reagents:
* A solution of diphenylamine in an alcohol-acetone mixture followed by irradiation with UV light at a wavelength of 336 nm.
* A solution of ethylenediamine in acetone.
* A 5% solution of potassium dichromate in a mixture of sulfuric and acetic acids.

GC-MS Study

The GC-MS study was conducted on a GCQ spectrometer from Finnigan MAT (USA).
* Separation of substances was carried out in a helium stream at a speed of 60 cm/s on a DB-1 column from J&W Scientific (USA) with a diameter of 0.25 mm, a phase layer thickness of 0.25 μm, and a length of 1.5 m.
* The injected sample volume was 1 μl.
* Injector temperature — 200 °C.
* Splitless injector mode.
* Column temperature: isothermal at 70 °C for 1 min, then programmed heating at a rate of 25 °C/min.
* Ion source temperature — 150 °C, interface — 250 °C.

Mass spectra of the separated substances were recorded in the chemical ionization mode with methane reagent gas in the negative ion mass range of 35 — 300 amu. Identification of HE was carried out by comparing the retention times and mass spectra of the substances in the studied samples and reference samples.

As a result, it was established that trace amounts of 2,4,6-trinitrotoluene (TNT) — a high explosive — are present in all swabs, and trace amounts of hexogen — a high explosive — are present in swabs from fragments from box No. 3 (item 8) and swabs (items 14, 15).

Thus, the composition of the detonated IED charge included TNT and hexogen — high explosives.

TNT and hexogen can be used as explosives both individually and in the form of mixtures with other components (for example, with ammonium nitrate, aluminum).

IC Method for Ammonium Nitrate Detection

To detect trace amounts of ammonium nitrate, studies were conducted using the IC method on a Varian Star liquid chromatograph (USA). Eluent delivery was carried out using a Varian model 9002 isocratic pump (USA).

To separate anions in the studied mixture, the following were used:
* An Elsian-6-Kank column from Elsiko (Russia) filled with anion-exchange resin.
* A 2x20 mm pre-column filled with grafted C18 phase with a particle size of 40 μm.
* A BTS AG suppression column from Biotronic (Germany).

Chromatography of the sample was carried out in isocratic mode with a carbonate buffer containing 0.002 M Na2CO3 and 0.002 M NaHCO3. Eluent flow rate 2 ml/min.

To separate cations in the studied mixture, the following were used:
* A BT IV KA column from Biotronic (Germany).
* A 2x20 mm pre-column filled with grafted C18 phase with a particle size of 40 μm.
* A BTS AG suppression column from Biotronic (Germany).

Chromatography of the sample was carried out in isocratic mode with a buffer containing 0.002 M HNO3. Eluent flow rate 2 ml/min.

Inorganic Component Detection

Detection of inorganic components was carried out by absorption in the UV region at a wavelength of 192 nm using a Varian Star model 9050 photometric detector (USA) and an Alltech model 550 conductometric detector (USA).

• Injection into the chromatograph was performed with a microsyringe and an injector with a 100 μl loop.
• Before injecting the studied samples, a blank experiment was conducted to check the purity of solvents and glassware.
• For calibration, standard freshly prepared solutions of anions in water in the concentration range of 0.1-10 μg/ml were used.

As a result, it was established that ammonium ions and nitrate ions are present in the aqueous extracts of swabs from all studied objects. Their background level was determined based on the results of the analysis of soil sample extracts.