Forensic Analysis and Differentiation of Black Powder and Black Powder Substitute Chemical Signatures by Infrared Thermal Desorption–DART-MS

Abstract

The trace detection and forensic analysis of black powders and black powder substitutes, directly from wipe-based sample collections was demonstrated using infrared thermal desorption (IRTD) coupled with direct analysis in real time mass spectrometry (DART-MS). Discrete 15 s heating ramps were generated, creating a thermal desorption profile that desorbed more volatile species (e.g., organic and semivolatile inorganic compounds) at lower temperatures (250 °C to 400 °C) and nonvolatile inorganic oxidizers at high temperatures (450 °C to 550 °C). Common inorganic components of black powders (e.g., sulfur and potassium nitrate) as well as the alternative and additional organic and inorganic components of common black powder substitutes (e.g., dicyandiamide, ascorbic acid, sodium benzoate, guanidine nitrate, and potassium perchlorate) were detected from polytetrafluoroethylene- coated fiberglass collection wipes with no additional sample preparation. IRTD-DART-MS enabled the direct detection of intact inorganic salt species as nitrate adducts (e.g., [KClO4+ NO3]−) and larger clusters. The larger ion distributions generated by these complex mixtures were differentiated using principal component analysis (PCA) of the mass spectra generated at two points during the thermal desorption profile (low and high temperatures), as well as at high in-source collision induced dissociation (CID). The PCA framework generated by the analysis of two black powders and five black powder substitutes was used to classify samples collected from a commercial firecracker containing both flash powder and black powder. The coupling of IRTD-DART-MS and multivariate statistics demonstrated the powerful utility for detection and discrimination of trace fuel-oxidizer mixtures.

Interpol review of detection and characterization of explosives and explosives residues 2016-2019

“…Forbes, T. and Verkouteren, J. reported on the Forensic Analysis and Differentiation of Black Powder and Black Powder Substitute Chemical Signatures by Infrared Thermal Desorption–DART-MS . As reported in their abstract, “The trace detection and forensic analysis of black powders and black powder substitutes, directly from wipe-based sample collections, was demonstrated using infrared thermal desorption (IRTD) coupled with direct analysis in real time mass spectrometry (DART-MS)” [ 401 ].…”

Trace detection and chemical analysis of homemade fuel-oxidizer mixture explosives: Emerging challenges and perspectives

“…In a related high temperature platform, Forbes et al incorporated infrared heating and traditional wipe sampling to thermally desorb organic and inorganic explosives (Figure 5). [64][65][66] Given the wide variability in infrared absorption of targeted compounds, this thermal desorber used infrared energy to rapidly heat a secondary energy storage component in direct contact with an inserted wipe. The infrared thermal desorption (IRTD) temperature profiles desorbed volatile components (e.g., sulfur or ascorbic acid) early in the profile and nonvolatile components (e.g., potassium perchlorate or potassium nitrate) late(r) in the profile.…”

Detection of fuel‐oxidizer explosives utilizing portable capillary electrophoresis with wipe‐based sampling

“…Detection of the target oxidizer species (nitrates and perchlorates) exhibited no detrimental effects, such as peak shifts or interfering peaks, from the additional components in these mixtures. A previous mass spectrometry analysis was used to verify the contents of these samples [33]. Unfortunately, the targeted nature and limited elution window of the system prohibited the detection of any of the other organic and inorganic fuels and oxidizers.…”