Laboratory and field experiments used to identify Canis lupus var. familiaris active odor signature chemicals from drugs, explosives, and humans

Abstract

This paper describes the use of headspace solid-phase microextraction (SPME) combined with gas chromatography to identify the signature odors that law enforcement-certified detector dogs alert to when searching for drugs, explosives, and humans. Background information is provided on the many types of detector dog available and specific samples highlighted in this paper are the drugs cocaine and 3,4-methylenedioxy- N-methylamphetamine (MDMA or Ecstasy), the explosives TNT and C4, and human remains. Studies include the analysis and identification of the headspace "fingerprint" of a variety of samples, followed by completion of double-blind dog trials of the individual components in an attempt to isolate and understand the target compounds that dogs alert to. SPME-GC/MS has been demonstrated to have a unique capability for the extraction of volatiles from the headspace of forensic specimens including drugs and explosives and shows great potential to aid in the investigation and understanding of the complicated process of canine odor detection. Major variables evaluated for the headspace SPME included fiber chemistry and a variety of sampling times ranging from several hours to several seconds and the resultant effect on ratios of isolated volatile components. For the drug odor studies, the CW/DVB and PDMS SPME fibers proved to be the optimal fiber types. For explosives, the results demonstrated that the best fibers in field and laboratory applications were PDMS and CW/DVB, respectively. Gas chromatography with electron capture detector (GC/ECD) and mass spectrometry (GC/MS) was better for analysis of nitromethane and TNT odors, and C-4 odors, respectively. Field studies with detector dogs have demonstrated possible candidates for new pseudo scents as well as the potential use of controlled permeation devices as non-hazardous training aids providing consistent permeation of target odors.

Fast Chromatographic Method for Explosive Profiling

“…A polydimethylsiloxane (PDMS) SPME 100 µm (Sigma, Bellefonte, PA, USA) fiber was exposed for 15 min to the headspace of each explosive sample at room temperature. PDMS was chosen for its polyvalent trapping properties and for its stability that allows field sampling, in addition to precedent set by other studies that investigated explosive detection [1,5,12,13]. …”

“…For the majority of these compounds, the source and function can be found in previous research [1]: Plasticizers (phthalates), stabilizers (amino benzoic compounds), nitroso and nitro compounds from the explosive, or degradation products. The resolution power of the GC×GC technique allowed for the separation of the volatile compounds in each sample in less than 5 min.…”

“…Different tools are used to achieve this task including detection dogs [1], ion mobility spectrometry (IMS) [2][3][4], gas chromatography (GC) [5], and liquid chromatography (LC) [6]. Nevertheless, one of the most accurate and sensitive means of screening for explosives remains the use of explosive detection dogs [1]. These canines receive special training to alert to potential traces of explosives in different conditions.…”

“…Several techniques have been developed previously that allow generation of vapor from explosives samples to provide a sufficient quantity of volatiles for analysis [8][9][10][11]. Solid phase micro-extraction (SPME) provides sufficient pre-concentration for most explosives samples and is therefore used widely [1,2,5,12,13]. Moreover, SPME is also used for volatile sample analysis in other forensic applications, such as chemical warfare agent detection [14], illicit drug detection [1], and decomposition odor monitoring [15].…”

“…For this reason, gas chromatography-mass spectrometry (GC-MS) methods are also used to provide a non-targeted approach that can generate a global characterization of the entire volatile signature [2,5]. Due to the low volatility of explosives, the minor components (e.g., components other than the active agents) are often targeted in research and focus on degradation products or source contamination [1,7]. In order to counteract the low vapor pressure, manufacturers add taggants to explosives such as 2,3-dimethyl-2,3-dinitrobutane (DMNB) to act as a marker when canines or instrumentation are used for detection.…”