Differentiation of oleoresin capsicum sprays based on their capsaicinoid profiles.

Oleoresin capsicum (OC) sprays, often referred to as 'pepper sprays', contain a solution of active compounds, exerting an irritating effect on the human body. The active component of OC sprays are capsaicinoids, obtained by extraction from peppers. The profiles (quantitative relations) of natural capsaicinoids depend on the plant material, they were extracted from. Pepper spray is a non-lethal weapon that should only be used for self-defense but is often used by criminals to attack and incapacitate victims. Evidence related to these types of incidents, such as containers, clothes of victims or suspects, as well as traces of substances found at the scene, are submitted to the forensic laboratory. The purpose of the analysis is to identify the ingredients of the preparation (especially active components) and compare the traces found on objects from the victim or the scene of the incident with the preparation from the can or traces found on objects related to the suspect. The study aimed to investigate the possibility of differentiating OC gases based on capsaicinoid profiles recorded in GC-MS analyses. Sixty-four gases from 12 different manufacturers were purchased and tested. The likelihood ratio (LR) approach was applied to the data expressing the relative capsaicinoids contents computed by integrating GC-MS signals. Two hypotheses were assumed that stated either common or different origins of the samples. Several LR models have been developed, and their performance has been controlled by the number of false positives and false negatives as well as empirical cross entropy. The research results showed that differentiation was very successful, with more than 90% of correct responses. The results obtained show that OC sprays may be distinguished, even if they were produced by the same producer presumably if produced using different batches of pepper extract.

Chromatographic analysis of the traces of 2-chlorobenzalmalononitrile with passive adsorption from the headspace on Tenax TA and Carbotrap 300.

The main purpose of the presented research was to check if CS agent (Chlorobenzylidenomalononitrile CAS 2698-41-1) can be separated from the forensic samples using passive adsorption from the headspace on the adsorption tubes and, if so, what are the optimal conditions of this process. Two different adsorbents were checked (adsorption tubes filled with Tenax TA and adsorption tubes filled with Carbotrap 300). Three different packages (gastight bags by Ampac, Nylon bags by BVDA and twist-off jars) were tried and the temperature range checked was 30°C-105°C. This research demonstrated CS is not volatile enough to enter the headspace in a gaseous form, therefore it cannot be adsorbed regardless of adsorbent, package, and temperature, in the investigated temperature range. In all the samples a product of CS hydrolysis this is 2-chlorobenzaldehyde (CAS 89-98-5) was detected. The presence of 2-chlorobenzaldehyde maybe therefore used as an indirect proof that the investigated sample was in contact with CS compound. 2-chlorobenzaldehyde is much more effectively adsorbed on Tenax TA than on Carbotrap 300. The other conclusion from this part of the research is that twist-of glass jars and nylon bags are not entirely gas-tight and should not be used as a package on the adsorption stage. Methanol is usually used for the extraction of irritating compounds from the samples, therefore the stability of CS agent in methanolic solutions was investigated. The research demonstrated that CS is unstable in methanol and hydrolyze to 2-chlorobenzaldehyde. This is most probably because, in the HPLC grade methanol which was used, a small amount of water is present. The hydrolysis is slower if the solution is stored in an amber glass vial and much faster when stored in transparent vials.

Substrate interferences in identifying flammable liquids in food, environmental and biological samples: case studies.

The analysis of samples for traces of ignitable liquids is most often connected with suspected arson cases. In such cases, samples taken from the point of origin of the fire are analyzed for the presence of ignitable liquids. However, sometimes, in cases not connected with arson, there is a need to detect and identify traces of ignitable liquids. Three examples of such cases are given in this paper. Aqueous samples (polluted water, juice and blood) were analyzed using a procedure routinely used in the analyses of fire debris. The procedure consists of passive adsorption of volatile organic compounds on Tenax, followed by thermal desorption and chromatographic analysis. Results showed that analysis of such untypical samples may be connected with unusual matrix effects, not frequently encountered in fire debris samples.

Chemical analysis of post explosion samples obtained as a result of model field experiments.

Five different explosives were detonated in a series of field experiments. Each experiment (detonation of the charge of each specific explosive) was repeated three times. The experiments were conducted under controlled conditions, exceeding those of research published so far. Detonated charges were uniform in size and, as far as possible, in shape. The explosives used originated from the same batch. Additionally, the same kind of electric detonators were used. Witness plates (sheets of galvanised steel 100 cm × 90 cm × 0.5 mm) were used to collect post-blast residues in a reproducible way. They were placed relatively close to the charge to minimise the influence of the wind. Samples were collected by systematic swabbing of the surface of the plate by acetone moistened cotton swabs. Samples were packed tight, transferred to the laboratory, and extracted with methanol. Extracts were concentrated by solvent evaporation, cleaned by centrifugation, and analysed using HPLC-DAD. Each extract was analysed three times and the mean value of the amount of the given explosive within the extract was calculated. For each of the explosive materials used the results of the repetition of the experiments proved them to be irreproducible. After each detonation of a specific charge different amounts of given explosives were found in post-blast samples. Also, the intuitively expected relationship between the distance from the charge and amount of post-blast residues were not observed. These results are consistent with previously published results of field experiments. The lack of reproducibility may be explained by differences in efficiency of detonation. The efficiency of a detonation may be influenced even by small differences in the shape of the charge as well as by the position and properties of the detonator. The lack of dependency between the amount of the explosive in the post-blast samples and the distance from the charge may be explained by the fact that during detonation, particles of unreacted explosives are not uniformly dispersed in all directions.

Comparison of new Ampac bags and FireDebrisPAK® bags as packaging for fire debris analysis.

The FireDebrisPAK(®) bags that were produced by Kapak were considered to be one of the best containers for fire debris. Kapak bags were discontinued; however, from July 2010, Ampac is offering a new packaging material. The aim of the presented research was to compare the properties (durability, background interferences, and permeability) of Kapak bags and packaging material offered by Ampac. The analysis was conducted by passive adsorption from the headspace with subsequent thermal desorption and analysis by GC-MS. The results proved that the properties of the compared materials are similar. Their greatest advantage is that they are impermeable for components of flammable liquids, so there is no danger of losing analytes or cross-contamination. Their one significant drawback is that they should not be exposed to temperatures above 80°C. At this temperature, they become soft, their inner layer is compromised (becomes sticky), and they emit some volatile organic compounds. Among them, there are compounds that constitute the components of some of flammable liquids.

PRAXIS--combined mu-Raman and mu-XRF spectrometers in the examination of forensic samples.

Recently, two analytical techniques--Raman and XRF spectroscopy--have been often applied in criminalistic examinations of different kinds of trace evidences. In this paper, the application of the new combined mu-Raman and mu-XRF spectrometer in analysis of multilayer paint chips, modern inks, plastics and fibres was evaluated. It was ascertained that the apparatus possesses real advantages and could be helpful in the identification of examined materials after some modifications, i.e. by adding an extra laser and decreasing the spot size of the X-ray beam.

Comparison of the effectiveness of Tenax TA and Carbotrap 300 in concentration of flammable liquids compounds.

The aim of research was to compare two adsorbents, Tenax TA and Carbotrap 300, to evaluate their usefulness as passive adsorbents of flammable liquids compounds. It was also to determine whether Carbotrap 300 could be used in a passive adsorption mode, contrary to manufacturer recommendations. To compare the adsorption properties and the thermal desorption efficiency for Tenax TA and Carbotrap, the components of test mixture were adsorbed and then chromatographically analyzed. The analysis was conducted by means of an automated thermal desorber coupled with a gas chromatograph and a mass spectrometer. This research established that although these adsorbents significantly differ from each other in adsorption properties, each of them can be successfully used for passive adsorption of ignitable liquids compounds. Tenax TA turned out to be more effective for the adsorption of nonpolar, high-boiling compounds, whereas Carbotrap is more effective for polar and volatile compounds. The examined adsorbents differ in their susceptibility to thermal desorption. For Carbotrap 300, after the analysis an additional treatment is required to remove the remnants of adsorbed compounds. With Tenax TA, this additional step is not necessary because the thermal desorption is sufficiently effective that this product is immediately ready for re-use.