- Development and validation of a new TD-GC/MS method and its applicability in the search for human and animal decomposition products
- E. Rosier, E. CuypersM. DekensR. VerplaetseW. DevelterW. Van de VoordeD. MaesJ.
- Université de Leuven - Analytical and Bioanalytical Chemistry
Différencier entre restes humains et animaux au moyen des composés volatiles libérés au cours de la décomposition est impossible tant que reste à établir quels sont les marqueurs volatiles spécifiques à la décomposition des tissus humains. L'identification de tels marqueurs permettrait de dresser les chiens "cadavre" plus efficacement (en fait de manière assez sûre pour que l'alerte d'un chien à un endroit où un corps a été présent, mais n'est plus là soit prise en compte dans les cours de justice), en attendant que soit conçu un dispositif capable d'oeuvrer aussi bien que le chien.
Cette étude décrit le développement et la valisation d'une nouvelle méthode analytique applicable à la recherche de tels marqueurs spécifiques.
E. Rosier, S. Loix, W. Develter, W. Van de Voorde, J. Tytgat, E. Cuypers
In this study, a validated method using a thermal desorber combined with a gas chromatograph coupled to mass spectrometry was used to identify the volatile organic compounds released during decomposition of 6 human and 26 animal remains in a laboratory environment during a period of 6 months. 452 compounds were identified. Among them a human specific marker was sought using principle component analysis. We found a combination of 8 compounds (ethyl propionate, propyl propionate, propyl butyrate, ethyl pentanoate, pyridine, diethyl disulfide, methyl(methylthio)ethyl disulfide and 3-methylthio-1-propanol) that led to the distinction of human and pig remains from other animal remains. Furthermore, it was possible to separate the pig remains from human remains based on 5 esters (3-methylbutyl pentanoate, 3-methylbutyl 3-methylbutyrate, 3-methylbutyl 2-methylbutyrate, butyl pentanoate and propyl hexanoate). Further research in the field with full bodies has to corroborate these results and search for one or more human specific markers. These markers would allow a more efficiently training of cadaver dogs or portable detection devices could be developed.
- During the decomposition of human and animal remains, a wide spectrum of volatile organic compounds (VOCs) is emitted in the environment. The past few years, the research to characterize this ‘smell of death’ has increased and a wide variety of compounds has already been identified: alkanes, alcohols, acids, esters, ketones, aldehydes, cyclic hydrocarbons, aromatic, sulphur- and nitrogen-containing compounds [1–19]. Pig remains are often used as human analogues (Table 1) because of their similarity in hair coverage, weight, fat to muscle ratio, gut fauna and biochemistry [5, 16, 20]. However, the VOC-profiles of human and animal remains were hardly compared, notwithstanding the fact that they could be interesting to find a human specific marker. The following research groups compared human and animal remains. Degreeff et al. reported that phenylethene and methyl benzoate were more specific for human than animal remains . Cablk et al. compared their experimental results of animal remains with literature results of human remains. They found 11 compounds published on human research which they could not detect in their animal study . Vass suggested that carbon tetrachloride, pentane, decane and undecane appeared to be human specific. Additionally, he saw that 2-methylbutanal was always greater than 3-methylbutanal in the animal remains he studied (pig, deer, dog, cat, squirrel and sheep). However, in human remains he noted that this phenomenon was reversed or that both compounds were equal to each other . Clearly, there are still inconsistencies in literature of the human specific compounds and more research has to be done.
- Ultimately, a variety of forensic disciplines could benefit from these human specific markers. Mainly in the search of human bodies or remains. Thanks to their good olfactory capacity, cadaver dogs are able to locate bodies [17, 21]. At this moment, mostly nonspecific compounds such as cadaverine and putrescine are used to train these dogs. They can find human cadavers with this training, but the use of artificial scents is highly debated. Cadaver dogs trained with these scents did not always react on real cadaver samples (data derived from dog handlers of the Federal Police in Belgium). Training aids appear to be an oversimplification of the decomposition odor . A human specific marker can be used to train cadaver dogs more efficiently and therefore win time to locate a body. Moreover, when a human specific marker is found, it might be possible to develop a portable device that is sensitive enough to locate human remains.
- The decomposition can be influenced by many environmental factors such as temperature, humidity, soil type, submersion of the body . Therefore, it is difficult to compare results of research groups that study the decomposing remains outdoors. In this study, we sampled the headspace of 6 human and 26 animal remains that decomposed for 6 months. This study was conducted in glass jars in laboratory environment to pre-concentrate and therefore easily sample the released VOCs. It is also a manner to standardize the methodology with control of the parameters such as temperature and moisture, as much as possible. These samples were collected and analyzed with a validated method using thermal desorber combined with gas chromatography coupled to mass spectrometry (TD-GC/MS) . When the VOC-profiles of human and animal remains were identified, principal component analysis (PCA) was applied on the results to search for (a) human specific marker(s). The aim of our study was to identify VOCs specific for human decomposition.