Detection of Trace Amounts of Ammonium Nitrate

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 from "Varian" (USA). The eluent was supplied using an isocratic pump model 9002 from "Varian" (USA).

Anion Separation

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

Chromatography of the sample was carried out in isocratic mode with a carbonate buffer containing 0.002 M $\text{Na}_2\text{CO}_3$ and 0.002 M $\text{NaHCO}_3$. Eluent flow rate: 2.0 ml/min.

Cation Separation

For the separation of cations in the studied swabs, the following were used:
* A BT IV KA column from "Biotronik" (Germany).
* The guard column mentioned above.
* A BT-S KG suppression column from "Biotronik" (Germany).

Chromatography of the sample was carried out in isocratic mode with a buffer containing 0.002 M $\text{HNO}_3$. Eluent flow rate: 2.0 ml/min.

Detection and Calibration

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

Injection into the chromatograph was performed with a microsyringe and an injector with a 100 μl loop. For chromatograph calibration, standard freshly prepared solutions of anions and cations in water in the concentration range of 0.1 - 10 μg/ml were used.

Results and Interpretation

• Ammonium ions and nitrate ions in the amount of $10^{-6} - 10^{-7}$ g were detected in the swabs from the studied objects.
• As is known from expert practice, nitrate ions and ammonium ions are present in trace amounts in swabs from places of contact of any surface with a mixed explosive containing ammonium nitrate in its composition.
• On the other hand, in everyday life and in the national economy, substances of organic and inorganic nature are widely used, which either directly contain the above-mentioned ions (for example, ammonium nitrate fertilizers) or form them during their decomposition (for example, aniline dyes, nitro-lacquers, etc.).
• It is not possible to unambiguously determine the source of origin of the detected ions based on the results of physicochemical studies.

Aluminum Particle Detection

In order to detect aluminum particles, the deposits on the filters remaining after filtration of the swabs were studied by the SEM-EDX method on a JSM-840 scanning electron microscope from "Jeol" (Japan) with an ISIS microprobe analyzer from "Oxford Instruments" (UK) at an accelerating voltage of 20 kV. The range of detectable elements is from beryllium to uranium.

As a result, it was established that in the deposits on the filters there are many silver-colored microparticles in the form of flat flakes of size...