•Chemotyping of R. lauricola showed growth patterns are reflected by volatiles.•Before day 15 alcohols, acetates, and esters are produced as VOCs.•After day 15 terpenes and hydrocarbons are produced as VOCs by MVA pathway.Volatile organic compounds (VOCs) in the headspace of the fungus Raffaelea lauricola have been monitored and identified over a twenty-eight day growth period. R. lauricola is an invasive and phytopathogenic fungus that was first identified in the United States in the mid-2000s. It is believed to be spread by a host beetle, Xyleborus glabratus, and is detrimental both to wild members of the Lauraceae family and to commercial avocado groves particularly in the Southeastern region of the country. The fungus causes the fatal laurel wilt disease, a result of the host tree shutting down its vascular system in order to halt the spread of the fungus. The current study identified the VOCs present in the headspace of R. lauricola over the initial growth stage using headspace solid phase microextracion-gas chromatography-mass spectrometry (HS-SPME-GC–MS). Results revealed the VOC dynamics of the fungus in culture, indicating that the initial growth period of the fungus may coincide with potential responses from the host trees that may recognize and respond to the pathogen when the fungal VOCs are produced as a result of primary metabolic processes. As fungal growth progresses past initial growth phases, the predominant compounds seen in the odor profile are hydrocarbons and terpenes, produced from secondary metabolic processes. The odor profile pattern for the twenty-eight day growth period did change with the stages of growth. Based on the information learned from this pilot study, a discussion is presented of possible host tree reactions to R. lauricola and implications for future experiments.

•Use of chemical analysis and canine detection of VOCs as complimentary techniques.•Identification of 9 common VOCs in headspace above avocado trees with laurel wilt.•Canines alert to most volatile compounds in the headspace of infected avocado trees.Raffaelea lauricola, a fungus causing a vascular wilt (laurel wilt) in Lauraceae trees, was introduced into the United States in the early 2000s. It has devastated forests in the Southeast and has now moved into the commercial avocado groves in southern Florida. Trained detection canines are currently one of the few successful methods for early detection of pre-symptomatic diseased trees. In order to achieve the universal and frequent training required to have successful detection canines, it is desirable to create accessible, safe, and long-lasting training aids. However, identification of odorants and compounds is limited by several factors, including both the availability of chemicals and the need to present chemicals individually and in combination to detection canines. A method for the separation and identification of volatile organic compounds (VOCs) from environmental substances for the creation of such a canine training aid is presented here. Headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to identify the odors present in avocado trees infected with the R. lauricola phytopathogen. Twenty-eight compounds were detected using this method, with nine present in greater than 80% of samples. The majority of these compounds were not commercially available as standard reference materials, and a canine trial was designed to identify the active odors without the need of pure chemical compounds. To facilitate the creation of a canine training aid, the VOCs above R. lauricola were separated by venting a 0.53 mm ID solgel-wax gas chromatography column to the atmosphere. Ten minute fractions of the odor profile were collected on cotton gauze in glass vials and presented to the detection canines in a series of field trials. The canines alerted to the VOCs from the vials that correspond to a portion of the chromatogram containing the most volatile species from R. lauricola. This innovative fractionation and collection method can be used to develop reliable and cost effective canine training aids.Download high-res image (192KB)Download full-size image

•Hand odor components have been identified as markers for gender and race/ethnicity.•Marker assortments have allowed human classification by race/ethnicity and gender.•Accuracy of human classification is validated and proven to be higher than chance.•Viability of forensic application is demonstrated for reported marker combinations.Human scent has been demonstrated to allow for the differentiation of individuals. The extent of this differentiation may allow scent to be used as a characteristic, capable of revealing information on an individual’s traits. The ability to use scent as a biometric human feature has enabled the use of scent as forensic evidence. However, its reliability, value, and admissibility in courts of law have sometimes been challenged as a result of limited scientific validation. Full acceptance of human scent evidence has been hindered by the limited availability of peer reviewed information that provides greater understanding of how human scent originates and how it may be used. The objective of this study is to report new data that further enhances our understanding of the value of human scent evidence and its acceptance in courts of law. In order to fulfill this objective, volatile organic compound combinations were identified as markers for race/ethnicity and gender from hand odor samples from 105 individuals. The accuracy of human classification by race/ethnicity and gender, on the basis of these markers, was determined and validated. Overall accuracies of 80% and 72% were obtained for the classification of subjects by gender and race/ethnicity, respectively. The results obtained demonstrate that the identified VOC marker combinations represent a viable resource for the classification and/or differentiation of persons of interest and, as such, may be considered a valuable forensic tool for subject identification.

•Results of this paper validate the reliability of canine evidence in court.•The odor profiles of snapdragon flowers were found to be statistically different than cocaine.•Methyl benzoate is not necessarily the dominant odor produced by snapdragon flowers.•Narcotic detection canines never falsely alerted to snapdragon flowers.In recent years, the high frequency of illicit substance abuse reported in the United States has made the development of efficient and rapid detection methods important. Biological detectors, such as canines (Canis familiaris), are valuable tools for rapid, on-site identification of illicit substances. However, research indicates that in many cases canines do not alert to the contraband, but rather to the volatile organic compounds (VOCs) that are released from the contraband, referred to as the “active odor.” In 2013, canine accuracy and reliability were challenged in the Supreme Court case, State of Florida v. Jardines. In this case, it was stated that if a canine alerts to the active odor, and not the contraband, the canine's accuracy and selectivity could be questioned, since many of these compounds have been found in common household products. Specifically, methyl benzoate, the active odor of cocaine, has been found to be the most abundant compound produced by snapdragon flowers. Therefore, the purpose of this study is to evaluate the odor profiles of various species of snapdragon flowers to assess how significantly methyl benzoate contributes to the total VOC profile or fragrance that is produced. Particularly, this study examines the VOCs released from newly grown snapdragon flowers and determines its potential at eliciting a false alert from specially trained detection canines. The ability of detection canines to differentiate between cocaine and snapdragon flowers was determined in order to validate the field accuracy and discrimination power of these detectors. An optimized method using headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS–SPME/GC–MS) was used to test the different types and abundances of compounds generated from snapdragon flowers at various stages throughout the plants’ life cycle. The results indicate that although methyl benzoate is present in the odor profile of snapdragon flowers, other compounds are present that contribute significantly, if not more, than that of methyl benzoate. Canine teams, from various police departments throughout South Florida, certified for narcotics detection, took part in this study. Two canine trials involving 21 canines teams were performed by exposing the teams to 4 different species of snapdragon flowers. Of the 21 canine teams tested, none alerted to the snapdragon flowers presented, while all (100%) alerted to real cocaine samples, the positive control. Notably, the results revealed that although methyl benzoate is produced by snapdragon flowers, certified narcotics detection canines can distinguish cocaine's odor profile from that of snapdragon flowers.

Trace biological materials contain volatile profiles that have yet to be evaluated to determine their value in forensic investigations. The volatiles released by different biological specimens (hand odor, hair, fingernails and saliva) collected from twenty individuals were identified using a solid phase microextraction–gas chromatography–mass spectrometry method. The human scent compounds from each specimen, per subject, were evaluated using Spearman rank correlation to assess the applicability of these compounds for the differentiation of individuals. The volatile organic compounds from each specimen type were readily identified and discriminated. When conducting inter-subject discrimination within a single specimen type, greater than 98.9% of the samples, or individuals, were differentiated for all specimen types. When conducting inter-subject discrimination among the four specimen types 99.6% of the samples were differentiated, at the 0.9 correlation coefficient threshold. Additionally, the only occurrence of cross-correlation between specimen types was observed between hair and fingernails while there were no cross-correlations with hand odor or saliva thereby demonstrating the distinctiveness of these specimens.

Human remains detection (HRD) canines are trained to locate human remains in a variety of locations and situations which include minimal quantities of remains that may be buried, submerged or extremely old. The aptitude of HRD canines is affected by factors such as training, familiarity with the scent source and environmental conditions. Access to appropriate training aids is a common issue among HRD canine handlers due to overly legal restrictions, difficulty in access and storage, and the potential biological hazards stemming from the use of actual human remains as training aids. For this reason, we propose a unique approach of training aid creation, utilizing non-contact, dynamic air-flow odor concentration onto sorbent materials. Following concentration, the sorbent material retains the odor from the scent source composed of volatile organic compounds. The sorbent material containing the odor can then be utilized as a canine training aid. Training materials prepared in this manner were tested under a variety of conditions with many HRD canines to demonstrate the efficacy of the new training aids. A high level of correct canine responses to the new training aids was achieved, approaching 90%, with minimal false positives.

In recent years, interest has increased regarding the identification of volatile organic compounds (VOCs) for metabolic profiling, human scent identification of the living and deceased, and diagnostic potentials for certain diseases that are known for its association with distinct odor. In this study, a method has been developed that is capable of sampling, identifying, and differentiating the VOCs present in various biological specimens of forensic importance (blood, breath, buccal cells, and urine) taken from the same individuals. The developed method requires a pretreatment step to remove targeted VOCs from the sampling apparatus prior to sampling of the individual specimens. The VOCs collected from the biological specimens were characterized by solid-phase microextraction and gas chromatography/mass spectrometry with ratios of the most abundant and frequent VOCs compared using qualitative and semiquantitative methods. Blood, breath, and buccal cells required extraction procedures ranging from 18 to 21 h in order to optimize the limit of detection, which averaged 5–15 ng across these specimens. The optimal method for measuring urine VOCs was complete in less than an hour; however, the limit of detection was higher with a range of 10–40 ng quantifiable. The demonstrated sensitivity and reproducibility of the methods developed allow for population studies of human scent VOCs from various biological specimen collection kits used in the forensic and clinical fields.

Sorbent materials used for the collection of human scent for investigative purposes have been shown to contain a variety of compounds reported as components of human scent. Many of the sorbents evaluated were biologically sterile, and it has been demonstrated that biologically sterile does not equate to “analytically clean” and the possibility exists for collected odor samples to be altered through interactions with the volatile organic compounds (VOCs) present initially on the sorbent material. The primary purpose of the study conducted was to evaluate various processes that can be applied to the sorbent materials to attain analytical cleanliness and eliminate the possibility of contamination of collected human odor samples. The chemical methods evaluated included Supercritical Fluid Extraction (SFE), Subcritical Water Extraction (SWE), traditional Soxhlet extraction, and autoclaving of sorbents. Optimization of the extraction parameters evaluated included temperature, pressure and extraction time, and the use of chemical modifiers such as methanol and water. Overall, SFE proved to be the most efficient method for producing sorbent materials free of human scent compounds.

In this study it is demonstrated that human odor collected from items recovered at a post-blast scene can be evaluated using human scent specific canine teams to locate and identify individuals who have been in contact with the improvised explosive device (IED) components and/or the delivery vehicle. The purpose of the experiments presented here was to document human scent survivability in both peroxide-based explosions as well as simulated roadside IEDs utilizing double-blind field trials. Human odor was collected from post-blast device and vehicle components. Human scent specific canine teams were then deployed at the blast scene and in locations removed from the blast scene to validate that human odor remains in sufficient quantities for reliable canine detection and identification. Human scent specific canines have shown the ability to identify individuals who have been in contact with IEDs using post-blast debris with an average success from site response of 82.2% verifying that this technology has great potential in criminal, investigative, and military applications.

Currently, in the field of odor detection, there is generally a wider variation in limit of detections (LODs) for canines than instruments. The study presented in this paper introduces an improved protocol for the creation of controlled odor mimic permeation system (COMPS) devices for use as standards in canine training and discusses the canine detection thresholds of piperonal, a starting material for the illicit drug 3,4-methylenedioxymethamphetamine (MDMA), when exposed to these devices. Additionally, this paper describes the first-ever reported direct comparison of solid phase microextraction–ion mobility spectrometry (SPME–IMS) to canine detection for the MDMA odorant, piperonal. The research presented shows the reliability of COMPS devices as low cost field calibrants providing a wide range of odorant concentrations for biological and instrumental detectors. The canine LOD of piperonal emanating from the 100 ng s−1 COMPS was found to be 1 ng as compared to the SPME–IMS LOD of piperonal in a static, closed system at 2 ng, with a linear dynamic range from 2 ng to 11 ng. The utilization of the COMPS devices would allow for training that will reduce the detection variability between canines and maintain improved consistency for training purposes. Since both SPME and IMS are field portable technologies, it is expected that this coupled method will be useful as a complement to canine detection for the field detection of MDMA.

The composition of human scent collected from the hands is of interest to the medical community as a mechanism to diagnose disease and the forensic community as a means to investigate canine scent discriminations. An extensive survey of the volatile organic compounds (VOCs) identified in the headspace of hand odor samples utilizing solid phase micro-extraction gas chromatography/mass spectrometry (SPME-GC/MS) has been conducted to determine the constituents of the human base odor profile. Sixty-three compounds were extracted from the collected odor samples. The composition included acids, alcohols, aldehydes, hydrocarbons, esters, ketones and nitrogen-containing compounds. The majority of the compounds detected (79.4%) were present in less than one third of the individuals sampled. Spearman correlation coefficient comparisons at a match/no-match threshold of 0.9 produced a distinguish ability of 99.67% across the population.

Arson is a serious crime but the cause of an arson fire can be difficult to find. Field portable electronic noses are evaluated in this study for their ability to detect the presence of accelerants in specific areas of a fire scene. Several common household materials are tested, with and without being burned with common accelerants, to determine the readings achieved with the electronic noses. Most samples were found to have detectable amounts of volatile compounds after burning. Some of the matrix materials alone were found to have levels similar to those of the accelerants. A proficiency test designed for accelerant detecting canines was replicated using one of the electronic noses. The detector was found to successfully discriminate between samples containing only matrix and those which also contained accelerants. However, it was not able to alert to the location of a small amount of accelerant spiked onto a pine board. For the extraction and collection of accelerants from fire debris, a portable dynamic headspace sampler is used. Volatile compounds are drawn off the headspace of a sample and deposited in an adsorbent filled tube. The desorbed samples are analyzed by gas chromatography/mass spectrometry. This method has demonstrated ability to concentrate small amounts of a range of volatile accelerants from burned debris. The three field portable instruments have shown to be useful and will continue to be evaluated for their ability to detect and collect accelerants in fire debris.

Despite the recent surge in the publication of novel instrumental sensors for explosives detection, canines are still widely regarded as one of the most effective real-time field method of explosives detection. In the work presented, headspace analysis is performed by solid phase microextraction (SPME)/gas chromatography–mass spectrometry (GC–MS), and gas chromatography–electron capture detection (GC-ECD), and used to identify dominant explosive odor chemicals seen at room temperature. The activity of the odor chemicals detected was determined through field trials using certified law enforcement explosives detection canines. A chemical is considered an active explosive odor when a trained and certified explosives detection canine alerts to a sample containing that target chemical (with the required controls in place). A sample to which the canine does not alert may be considered an inactive odor, but it should be noted that an inactive odor might still have the potential to enhance an active odor's effect. The results presented indicate that TNT and cast explosives share a common odor signature, and the same may be said for plasticized explosives such as Composition 4 (C-4) and Detasheet. Conversely, smokeless powders may be demonstrated not to share common odors. The implications of these results on the optimal selection of canine training aids are discussed.

This article reviews the use of dogs as chemical detectors, and the scientific foundation and available information on the reliability of explosive detector dogs, including a comparison with analytical instrumental techniques. Compositions of common military and industrial explosives are described, including relative vapor pressures of common explosives and constituent odor signature chemicals. Examples of active volatile odor signature chemicals from parent explosive chemicals are discussed as well as the need for additional studies. The specific example of odor chemicals from the high explosive composition C-4 studied by solid phase microextraction indicates that the volatile odor chemicals 2-ethyl-1-hexanol and cyclohexanone are available in the headspace; whereas, the active chemical cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) is not. A detailed comparison between instrumental detection methods and detector dogs shows aspects for which instrumental methods have advantages, a comparable number of aspects for which detector dogs have advantages, as well as additional aspects where there are no clear advantages. Overall, detector dogs still represent the fastest, most versatile, reliable real-time explosive detection device available. Instrumental methods, while they continue to improve, generally suffer from a lack of efficient sampling systems, selectivity problems in the presence of interfering odor chemicals and limited mobility/tracking ability.

Sorbent materials used for the collection of human scent for investigative purposes have been shown to contain a variety of compounds reported as components of human scent. Many of the sorbents evaluated were biologically sterile, and it has been demonstrated that biologically sterile does not equate to “analytically clean” and the possibility exists for collected odor samples to be altered through interactions with the volatile organic compounds (VOCs) present initially on the sorbent material. The primary purpose of the study conducted was to evaluate various processes that can be applied to the sorbent materials to attain analytical cleanliness and eliminate the possibility of contamination of collected human odor samples. The chemical methods evaluated included Supercritical Fluid Extraction (SFE), Subcritical Water Extraction (SWE), traditional Soxhlet extraction, and autoclaving of sorbents. Optimization of the extraction parameters evaluated included temperature, pressure and extraction time, and the use of chemical modifiers such as methanol and water. Overall, SFE proved to be the most efficient method for producing sorbent materials free of human scent compounds.