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 degrees C-105 degrees 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. (C) 2019 Elsevier B.V. All rights reserved.