A Comparison of Common Swabbing Materials for the Recovery of Organic and Inorganic Explosive Residues

Abstract

The efficiency of solvent based extraction methods used to remove explosive residues from four different swab types was investigated. Known amounts of organic and inorganic residues were spiked onto a swab surface with acetonitrile or ethanol:water combined with ultrasonication or physical manipulation used to extract the residues from each swab. The efficiency of each procedure was then calculated using liquid chromatography-ultraviolet detection for organic residues and ion chromatography for inorganic residues. Results indicated that acetonitrile combined with physical agitation proved to be the most efficient method; returning analyte recoveries c. 95% for both alcohol based swabs and cotton balls. Inorganic residues were efficiently extracted using ethanol:water, while the use of acetonitrile followed by water significantly reduced the recovery of inorganic residues. Swab storage conditions were then investigated with results indicating decreased storage temperatures are required to retain the more volatile explosives.

Investigating TNT loss between sample collection and analysis

“…However, Song-im reports using a 10 minute sonication step during swab extractions [14]. Similarly, DeTata suggests that the use of a sonication step will reduce any possible variation which may occur from the action of manual agitation with a Pasteur pipette [1]. From the sonication trials performed within the current work, the inclusion of a sonication step was deemed beneficial for 2,4-DNT recovery, as shown in Figure 1.…”

“…It is therefore vital to be able to detect any traces of explosives present in samples submitted to a forensic laboratory. High explosives, such as TNT (2,4,6-trinitrotoluene), have limited non-explosives uses and a 2 relatively low prevalence in the environment [1][2][3]. The detection of TNT can, as a consequence, be indicative of contact between a surface and an explosive, with a potentially unlawful origin [4,5], or can provide evidence of secondary transfer of such materials.…”

“…These often have a low persistence in the environment and must be recovered rapidly [6]. Explosives residues are typically collected from post-explosion debris, as well as from other possible explosives sources, such as the hands or clothing of a suspect [4], by swabbing using cotton swabs wetted with an organic solvent [1]. Swab extracts may then be analysed using a variety of techniques, such as gas chromatography (GC)-and liquid chromatography (LC)-based techniques [4].…”

A Fast Liquid Chromatography Tandem Mass Spectrometric Analysis of PETN (Pentaerythritol Tetranitrate), RDX (3,5-Trinitro-1,3,5-triazacyclohexane) and HMX (Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) in Soil, Utilizing a Simple Ultrasonic-Assisted Extraction with Minimum Solvent

“…In 2013, a group of explosives including RDX, HMX and PETN were analyzed using HPLC-UV after swabbing from soil and extraction of the swabs. 40 Swabs are first wetted with a suitable solvent before sampling and left to stand for 15 min after sampling. The swab was then extracted using a minimum of 5 mL of the solvent combined with physical agitation.…”

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

“…A number of studies have thus evaluated various swabbing materials, solvents or extraction procedures in the recovery of both organic and inorganic explosives [13][14][15][16][17][18][19][20]. The findings of these studies have been varied, with the best swabbing media and wetting or extraction solvents often differing according to the recovery surface or target analytes utilised [15][16][17].…”