Mapping explosive residues on galvanized pipe bomb fragments using total vaporization solid phase microextraction (TV-SPME)

Abstract

Solid phase microextraction (SPME) is a popular sampling technique whereby analytes are sorbed to a coated fiber and subsequently desorbed into an analytical instrument. In headspace SPME, analytes partition between the sample, the headspace above the sample, and the SPME fiber coating. In total vaporization SPME (TV-SPME), sample extracts are heated until both the solvent and analytes completely vaporize, whereupon the analytes partition between the vapor phase and the SPME fiber. In this study, TV-SPME using a polyethylene glycol fiber was coupled with fast gas chromatography/mass spectrometry to identify components of double-base smokeless powder (DBSP). Nitroglycerin (NG), diphenylamine (DPA) and ethyl centralite (EC) were separated in under 5 min. For NG, the optimal sample volume (70 mL), extraction temperature (60 C) and extraction time (20 min) resulted in a method that was over twelve fold more sensitive than traditional liquid injection and with a detection limit below 1 ppb. This method was then used to quantify DBSP residue on post-blast debris from five galvanized steel pipe bombs. The mean concentration of NG on the fragments was 0.25 ppm (w/w). An average of 1.01 mg of NG was recovered from the devices. Finally, the distribution of NG could be "mapped" by tracking the original locations of each fragment within the device. These maps showed that the distribution of NG was far from uniform. In fact, the concentration of the NG on fragments originating from the end caps was several fold higher than in other locations. This finding can help guide the selection of bomb fragments for chemical analyses in real-world scenarios.

Optimization of total vaporization solid-phase microextraction (TV-SPME) for the determination of lipid profiles of Phormia regina, a forensically important blow fly species

“…The fiber is then desorbed in the inlet of a GC or LC [1,2]. This paper will discuss the use of total vaporization solid phase microextraction (TV-SPME), which is a highly-sensitive technique whereby the totality of the liquid aliquot is vaporized prior to sampling, simplifying the equilibria inside the sample vial and maximizing the amount of analyte available in the headspace [3,4]. TV-SPME can analyze relatively large volumes (~50 -100 µL) of organic extracts, and the choice of fiber coating chemistry can be used to advantage based upon the solvent and analyte(s) [5,3,6].…”

Optimisation of recovery protocols for double-base smokeless powder residues analysed by total vaporisation (TV) SPME/GC-MS

“…Previous work by Bors et al employed TV-SPME/GC-MS for the recovery of DBSP residues from steel pipe bomb device fragments [34]. Although the device itself is a key source of postblast residues, traces may also be recovered from "witness" materials surrounding the explosive charge [38].…”

“…Bors for DBSP analysis [34] in order to provide a shorter analysis time. Samples were incubated for 1 minute at 60 °C, followed by a 5 minute extraction onto a 100 µm polydimethylsiloxane (PDMS) SPME fibre.…”

“…This method has been demonstrated as offering greater sensitivity than liquid injection or headspace or immersion SPME [31][32][33], and has been successfully applied to the detection of smokeless powder residues on steel pipe bomb fragments [34]. The optimised parameters were then applied to post-blast residues deposited on witness materials following detonation of a pipe bomb device.…”

Chemical analysis of racing fuels using total vaporization and gas chromatography mass spectrometry (GC/MS)

“…An important note is that the internal volume of a nominal 20 mL headspace vial is actually larger (e.g., 20.9 mL), which has a small but important effect on the calculated volume 8 . The theory and experimental requirements for coupling total vaporization to solid phase microextraction (TV-SPME) have been discussed previously, as well as the application of TV-SPME to determining nicotine in hair and post-blast explosive residue on bomb fragments 7,8 . As with any quantitative SPME method, the temperature and time of exposure of the SPME fiber to the sample vapor must be both accurate and precise, hence the use of an auto-sampler is required.…”