Identification of thiocyanates by Gas Chromatography – Mass Spectrometry in explosive residues used as a possible marker to indicate black powder usage

Abstract

Black Powder (BP) is one of the most common improvised explosives, due to broad access in precursors and simple home-made preparation. Deflagration of black powder results in residues the chemical analysis of which presents limitations and has been performed with several techniques until today; nevertheless, Gas Chromatography–Mass Spectrometry (GC–MS) has never been used. In this study, a simple experimental protocol has been developed towards black powder residues identification, using GC–MS. The sample preparation does not require specialized equipment. Derivatization of thiocyanates coming from BP deflagration and identification of the relative derivative (PBF-SCN) was achieved by monitoring ions m/z 239, 181 and 161. This characteristic derivative was used as a marker to indicate BP usage. The protocol was optimized by investigating individually all experimental parameters and it was evaluated for false positives and negatives. Repeatability and limit of detection were calculated to be %RSD 7.67 and < 1 mg, respectively. No interference coming from other ingredients that might co-exist in BP residues was observed. This protocol may be applied directly and without previous preparation to evidence coming from cases of explosions, thus practically contributing in BP residues identification.