Sampling of explosive residues: The use of a gelatine-based medium for the recovery of ammonium nitrate

Abstract

Forensic scientists must be able to recover traces of any original explosive materials not consumed in the detonation, in a careful controlled manner to aid a crime reconstruction. In current sampling techniques, the collection efficiency of post-blast residue is highly variable and often dependent on the swabbing materials and solvent systems used. To address these method limitations, this study presents a gelatine-based sampling medium and assesses its capabilities for the collection of ammonium nitrate.Common surfaces were spotted with a known concentration of ammonium nitrate, the unset gel applied, allowed to set, and then peeled from the surface. The gel was dissolved, and solid phase extraction employed to isolate the target explosive compound and remove the constituents of the gel.The eluate was concentrated and subsequently analysed and quantified. Overall, the gel formulation was able to collect ammonium nitrate from all of the test surfaces, with recoveries ranging from 0.1% to 61.7%. This study presents a gelatine-based formulation that has the potential to become a valuable asset in the forensic tool kit for the collection of explosive traces. A key attribute of the gel is that it offers an alternative recovery tool to conventional swabbing and solvent extraction methods.

Hydrogels: From Design to Applications in Forensic Investigations

“…The analysis and quantification of the eluate were performed afterward. This hydrogel has proven to be a good trace evidence collection forensic tool kit [74] . These on‐site, rapid, and easy collection and detection of trace evidence by hydrogels make them a novel biofriendly approach for forensic investigation (Figure 6).…”

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“…They focus on aspects of the investigation, methods of forensic examination regarding the determination of air, water, and land pollution, including due to the activities of non-governmental organizations. Therewith, the issue of sampling remnants of explosives using a gelatine base stays relevant (Amaral et al, 2020).…”

A fresh scientific look at transfer and persistence: From a materials science and tribology perspective

“…explosive [33][34][35] and gunshot residues (GSR) [36][37][38][39][40][41], and soil [42][43][44][45][46], as well as other less commonly encountered traces including glitter [47], fragrances [48][49][50], lipsticks [51], petrol [52], and polyurethane foam [53]. While valuable, such research tends to be very material-dependent, introducing specific parameters and interpretations that may have actually impeded the recognition of underlying foundational factors that could apply to most material types.…”

“…To date, most of the TPPR experimental work reported has focused on textile fibers [5–7,10–14] and glass [8,9,15–17]. Other authors have since investigated traditional trace evidence types like hair [18–20], paint [21–25], botanical and biological material [26–32], explosive [33–35] and gunshot residues (GSR) [36–41], and soil [42–46], as well as other less commonly encountered traces including glitter [47], fragrances [48–50], lipsticks [51], petrol [52], and polyurethane foam [53]. While valuable, such research tends to be very material‐dependent, introducing specific parameters and interpretations that may have actually impeded the recognition of underlying foundational factors that could apply to most material types.…”