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Abstract
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The detection and identification of irritating compounds - the active ingredients of "pepper sprays", also called "tear gases" - are common types of analysis conducted in forensic laboratories. The tear gases available on the market contain, as active ingredients, natural capsaicinoids extracted from pepper (OC), the synthetic capsaicinoid PAVA (pelargonic acid vanillylamide), CS (chlorobenzylidenemalononitrile) or, very rarely, CN (2-chloroacetophenone).
Because of differences in volatility, different methods are used to separate irritants from samples. CS and CN are volatile; therefore, the best method of separation is adsorption from the headspace of a sample. Capsaicinoids are not volatile enough, and they must be extracted with a solvent. Separated compounds are analysed using gas chromatography with mass spectrometry (GC-MS).
The aim of this paper is to present an effective procedure which is used in the analyses of irritants. This procedure is explained in detail based on the examples of four real cases.
To detect and identify CS and CN, passive adsorption from the headspace was conducted on Tenax TA tubes, with subsequent thermal desorption and GC-MS analysis (Case 1 and 3). Traces of CS were detected on the clothes of the suspect two weeks after the incident (Case 1). CN was identified as the active ingredient of grey powder, which was found in the car of the victim and in the garage belonging to the suspected person (Case 3).
PAVA and natural capsaicinoids (OC) were effectively separated by solvent extraction with methanol (Case 2 and 4). In Case 2, PAVA - the active ingredient identified in the spray secured from the suspect - was also found on the clothes of the victim. In Case 4, the available information about the samples (clothes of the victim) was that they might have been sprayed with OC or CS spray; therefore a two-step procedure was applied. Headspace analysis was conducted as the first step, to check for the presence of CS as well as solvents and other volatile ingredients of formulations. The second step was solvent extraction of pieces cut from the clothes of the victim. As a result, traces of OC spray were found and, on the basis of the profile of natural capsaicinoids, one out of two sprays was identified as the one which was probably used.
The cases described in this paper show that the presented procedure enables detection of all irritating compounds which may be found in tear gases available on the market
Key words
Pepper spray; Tear gas; Capsaicin; CS; PAVA; Headspace; Tenax TA.
Language: en |