Forensic Chemistry最新文献

Human remains detection dogs (HRDDs) play vital roles in forensic investigations and search and rescue missions by detecting decomposing human remains. However, there is a lack of standardized training protocols globally. This study evaluates various ethically sourced HRDD training aids, including amputated limbs, blood, and teeth used by the Ontario Provincial Police (OPP). Expanding on prior research, this study assesses amputated limbs stored outdoors, bone, tissue, blood, and teeth. The volatile organic compound (VOC) profiles of these aids are compared to cadavers decomposing at the Research in Experimental and Social Thanatology (REST) facility. The results highlighted that the combined VOC profile from all HRDD training aid types demonstrates a 68% similarity to REST cadavers, emphasizing the potential benefit of exposing HRDDs to a diverse range of training aids. This is because the similarities in VOC profiles of individual training aid types (amputated limbs stored indoors, bone, blood, tissue, amputated limbs stored outdoors, teeth) with REST cadavers were lower than 68%. Teeth (without organic matter) were identified as the least ideal training aid for enabling dogs to detect cadavers based on VOC profiles and HRDD responses. However, training on teeth may be required for operational needs, particularly when HRDDs need to locate teeth during field searches. This study also highlights the effectiveness of using amputated limbs and blood together as they comprise a majority of the 68% VOCs found similar to the REST cadavers and elicit desirable HRDD responses to decomposition odor.

New psychoactive substances (NPS) are present in the drug market and can be used as legal substitutes, making enforcement difficult. One of the classes of NPSs is the phenylethylamines, among which 25R-NBOHs (with R being a halogen or an alkyl group) are included. These compounds degrade when subjected to gas chromatography-mass spectrometry (GC–MS), one of the techniques routinely used to identify illicit substances, thereby complicating their identification. This study conducted the identification of NBOH samples using FTIR, XRD, and GC–MS techniques, as well as thermal analysis to obtain information that may assist in the development of new methods for the analysis of these synthetic substances. ATR-FTIR spectra presented characteristic bands of 25R-NBOH compounds (R = Br, Cl, Et, I). The UV–Vis spectra of the 25R-NBOH (R = Br, Cl, I) and 25E-NBOH samples showed a different profile, which may serve as a means to differentiate these compounds. The crystalline structure of the compounds was confirmed by comparing the experimentally obtained diffractograms with the diffraction patterns calculated using data from the Cambridge Crystallographic Data Center (CCDC) database. Thermal analysis indicated that the samples were not pure, confirming the FTIR and XRD analyses, which revealed the presence of impurities and the onset of sample degradation.

Carfentanil, remifentanil, and sufentanil are potent fentanyl analogues that are regularly mixed with illicit drugs causing many overdose deaths. Chemical impurity profiling of these drugs is a well-established technique for linking evidence found at a crime scene to other seized samples. The current study aims to expand the application of impurity profiling to metabolized samples to find synthesis specific markers. This is particularly relevant when the drug has been consumed, and no intact material is present at a crime scene. Carfentanil, remifentanil, and sufentanil were synthesized according to the Ugi or 7-step method and benzylfentanyl was produced using the Siegfried method. After in-vitro metabolism with human liver microsomes, the samples were analyzed by gas chromatography-mass spectrometry (GC–MS) and liquid chromatography high resolution tandem mass spectrometry (LC-HRMS/MS). Characteristic markers were found by applying a match criterion approach and principal component analysis (PCA). The precursors 4-ANBP, aniline, and N-phenylacetamide and several metabolites were identified in post-metabolism samples, indicating that specific synthesis information is retained after in-vitro metabolism. The detected levels were in line with concentrations reported in case work. In addition, LDA was applied to maximize discrimination between synthesis methods and to establish likelihood ratios (LRs). Calibrated LR values were in the range of 0.083 to 16 with very low false positive and false negative error rates. In conclusion, the presented work demonstrates the possibility of combining chemical profiling and retrospective biomarker analysis to obtain information about the synthesis method, which could be useful for forensic reconstructions and attribution investigations.

Polymeric composite materials with layered structures have increasingly gained importance as, for specific applications, the required properties cannot be achieved with one single material; thus, for example, multi-layer polymers or special surface coatings are employed.

None of the conventionally available techniques enables a comprehensive characterization of composite materials, including depth-resolved information about their organic and elemental constituents.

In this work, a previously introduced approach enabling the direct characterization of the organic and inorganic constituents of solid polymer samples was further developed and optimized for depth profiling analysis of stacked layer polymers. For this purpose, the ablation chamber’s washout behavior and transfer line’s transport efficiency were improved. Chemometric methods were applied for the data analysis to gain greater insight and enable more precise differentiation, comparison and classification.

The work investigates the feasibility of the developed approach by analyzing a multi-layer stacked polymer sample created from nail polishes and using cluster analysis on the data collected with the bimodal detection. The layers of the sample could be differentiated by their organic and elemental constituents’ fingerprints, achieving a depth resolution of 7 µm.

In the ensuing investigation after an explosion, determining the explosive used is of prime importance to establish investigative leads. Post-blast samples have many interferences and considerations that make quick, reliable identification a challenge. The use of a novel subsampling technique with DART-HRMS provides the ability to quickly detect and identify explosive residue after detonation. Simulated improvised explosive devices were constructed with a variety of materials and detonated with the help of the Montgomery County Fire Marshal’s Office (TX). Post-blast debris was subsequently collected and swabbed with a novel subsampling technique, utilizing filter paper. This filter paper was then introduced into the DART gas stream, with an internal standard to minimize potential false negatives. After introducing explosive residue from swabbed post-blast substrates, characteristic ions of selected constituents of smokeless powder including diphenylamine, ethyl centralite, di-n-butyl phthalate, and nitroglycerin were detected and confirmed through comparison of accurate mass measurements to theoretical exact masses. Additionally, characteristic ions of 2,4,6-trinitrotoluene (TNT) and Royal Demolition eXplosive (RDX) were also detected using this technique. Overall, the detection of characteristic ions was more successful when recovering residue from plastic compared to wood or metal, with success rates routinely at 100%. Implementing this screening technique enables rapid detection and reliable identification of explosive residue in a detonation incident. The developed subsampling technique provides practitioners with a practical method of screening post-blast debris in a laboratory setting, requiring minimal sample preparation.

Occasionally, trace evidence¹-casework faces major challenges, as not only suitable analytical methods must be available for relevant technical products and their traces, but background information regarding market or manufacturing processes must also be collected. Furthermore, analytical and forensic benefit are supposed to go together, in certain cases even under great time pressure. Given the focus of forensic service providers on individual traces, trace evidence work areas may not always be well prepared, particularly for products for which there are no collection traditions. On the basis of three fictitious case studies, an approach based on division of labor is presented and its advantages and disadvantages are discussed.

Post-explosion residue analysis is vital in forensic chemistry, providing valuable insights into incidents involving explosives. One significant challenge in this field is preserving samples for long-term storage for reanalysis. Presently, many laboratories conducting post-explosion analyses worldwide do not retain samples for reanalysis purposes, since the extraction process for sample preparation often necessitates the complete consumption of the scarce material. Even in cases where a portion of the material remains, such as a swab, it is difficult to ensure its representativeness and select a specific portion for preservation. One possible solution to overcome this challenge is to consider preserving the extracts used in the analyses for potential reanalysis. However, the stability characteristics of these extracts are currently unknown. The results presented in this article provide valuable insights into the feasibility of long-term storage for samples containing target analytes in extracts from post-explosion/burning residues of frequently encountered fuel-oxidizer explosive mixtures, such as flash powder, explosive emulsion, and black powder. These results shed light on the potential viability of preserving such extracts for future reanalysis, offering promising prospects for enhancing forensic investigations in this field. Based on the current findings, it has been demonstrated that the aqueous extracts can be effectively preserved as long-term storage samples for a minimum of 24 months, encompassing all the studied explosives. Only cyanate ion showed significant degradation among the 27 compounds studied. Additionally, the organic extract, specifically in the case of emulsion explosive, can be maintained for at least 12 months.

A series of N,N-disubstituted piperazines were synthesized containing the structural elements of meta-chlorophenylpiperazine (mCPP) in combination with methoxybenzyl-, and dimethoxybenzyl substituents to yield nine N,N-disubstituted piperazine compounds. These nine potential designer-like drug analogs were prepared based on common designer trends and regioisomeric differentiation was based on gas chromatography-mass spectrometry (GC–MS) and gas chromatography-vapor phase infrared (GC–vpIR) studies. The compounds in this study have not been reported as drugs of abuse at this time. However, commercial availability of precursor chemicals including mCPP suggests the possibility of further designer exploration. Capillary GC separation showed the regioisomers to elute according to the position of aromatic ring substitution and/or the degree of substituent crowding on the aromatic ring. Numerous electron ionization (EI) mass spectral fragment ions occur via processes initiated by one of the two nitrogen atoms of the piperazine ring. The major EI-MS fragment ions observed in all nine spectra occur at m/z 195 from the loss of the substituted benzyl radical and the cation at m/z 56 (C₃H₆N)⁺ from the piperazine ring. Unique radical cations at m/z 136 and m/z 152 are characteristic of the 2,3- and 3,5-dimethoxybenzyl isomers, respectively. The vapor phase infrared spectra for all nine compounds show a strong absorption band in the 1591–1593 cm⁻¹ region indicative of the chloroaniline moiety. Numerous bands in the 1600–650 cm⁻¹ region provide data for the differentiation of the methoxy and dimethoxybenzyl ring substitution patterns. Thus, a combination of EI-MS and vapor phase IR allow for the differentiation and specific identification of each regioisomer in this study.

Benzodiazepine (BZD) misuse has increased in the last decade, making its occurrence in criminal cases more commonplace. The detection of BZD in complex biological samples is challenging since they are usually found in small concentrations, requiring the development of sensitive and fast-to-execute methods. In this study, the application of direct analysis in real time – high-resolution mass spectrometry (DART-HRMS) was evaluated in the detection of 10 benzodiazepines (diazepam, oxazepam, chlordiazepoxide, temazepam, alprazolam, flunitrazepam, bromazepam, clonazepam, lorazepam, and midazolam) in ante and postmortem blood samples. Moreover, an ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) approach was developed by full factorial design as a clean-up step before the DART-HRMS analysis. DART-HRMS was capable of qualitative detection of all evaluated BZD in raw antemortem blood samples at concentrations as low as 10 µg mL⁻¹. The UA-DLLME DART-HRMS approach was linear for the 10 BZD in the range of 1 to 10 µg mL⁻¹, with recoveries ranging from 78.5 to 119.5 %, a precision lower than 36 % at 1 µg mL⁻¹, and limits of detection varying between 0.25 and 0.50 µg mL⁻¹. Moreover, the UA-DLLME DART-HRMS method was efficiently applied to postmortem blood samples from criminal cases, enabling the detection of BZD. The developed method facilitated the analysis of 10 BZD in ante and postmortem blood samples, offering a quick sample extraction that linked to the DART-HRMS can be used as a fast and reliable triage method for regulatory screening purposes and could be readily integrated into routine forensic analysis workflows in a high throughput manner.

Establishing links between starting materials and products is highly valuable in the investigation of the use of toxic chemicals for illicit purposes. In this study, impurity profiling was performed on starting materials and their synthesis product, 2-([dimethylamino]methyl)pyridin-3-yl dimethylcarbamate, an intermediate compound in the production route for the carbamate class of Chemical Warfare Agents. The aim was to link the five commercial starting materials to the correct synthesis products. Initially, the intermediate compound was synthesized using different batches of the two starting materials (2 plus 3 batches), producing six unique combinations. All synthesis batches and the different starting materials were analysed by gas chromatography-high resolution mass spectrometry (GC-HRMS). Chemometrics analyses were conducted with principal component analysis and orthogonal projections to latent structures discriminant analysis to extract chemical impurity profiles and to build supervised classification models.

Additionally, 12 test set samples, produced using the same starting materials by two different chemists in another laboratory, were analysed by GC-HRMS. A classification model able to distinguish all supplier combinations was successfully created and used to link the test set samples to their corresponding starting material.

Furthermore, a new set of synthesis samples was extracted with a work-up procedure before analysis to investigate the effect of higher sample purity on the classification model. The results show that linking the synthesis products to their starting materials was successful for one of the starting materials, despite the purification procedure.