Analytical Methods and Results

HPTLC Analysis

• HPTLC Silica gel 60 F 254 plate by Merck (Germany)
• Volume of the applied sample: 40 μl
• Eluent: benzene
• Eluent rise height from the start line: 50 mm
• Control sample: acetone solution of the most well-known high explosives (TNT, RDX, HMX, PETN, nitroglycerin, tetryl, and picric acid).

The presence of explosives was established by matching the relative mobility values of the substance spots on the chromatograms of the test 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 UV irradiation at a wavelength of 366 nm and a solution of ethylenediamine in acetone.

GC-MS Study

The GC-MS study was carried out on a GCQ spectrometer by Finnigan MAT (USA).

• Separation of substances was carried out in a helium flow at a speed of 50 cm/s on a DB-5MS column by J & W Scientific (USA) with a diameter of 0.25 mm, a stationary phase layer thickness of 0.25 μm, and a length of 10 m.
• The volume of the injected sample was 1 μl.
• Injector temperature: 200 °C.
• Splitless injector mode.
• Column temperature: isothermal 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 mass range of negative ions 35-300 amu. Identification of explosives was carried out by comparing the retention times and mass spectra of the substances in the test samples and reference samples.

Findings

As a result of the conducted studies, it was established:

• In swabs from the substance described in p. 5, and from the raincoat (p. 2), trace amounts at the level of $10^{-6} – 10^{-7}$ g of cyclotrimethylenetrinitramine (RDX) and 2,4,6-trinitrotoluene (TNT) – high explosives – were found.
• In acetone swabs from different places of the inner part of the container (p.p. 8-10), trace amounts at the level of $10^{-7} - 10^{-8}$ g of RDX were found.
• In swabs from the substances described in p.p. 4, 6, and from the cloth bag (p. 1), trace amounts at the level of $10^{-8} - 10^{-9}$ g of TNT were found.

Other high explosives (HMX, PETN, tetryl, trinitroglycerin, and picric acid) at the level of $10^{-9} - 10^{-11}$ g (the detection limits for various substances by these analysis methods) were not found in the swabs.

As is known, TNT and RDX are widely used for the manufacture of industrial mixed compositions, which may include ammonium nitrate and aluminum in the form of powder or dust as components.

Ammonium Nitrate Detection

The detection of trace amounts of ammonium nitrate (a component of ammonium nitrate explosives) in the swabs was carried out by the IC method on a Star liquid chromatograph by Varian (USA). The eluent was supplied using an isocratic pump model 9002 by Varian (USA).

For the separation of anions in the studied swabs, an Elsian-6-Kank column by Elsico (Russia) was used, filled with anion-exchange.