Forensic applications of isotope ratio mass spectrometry—A review

Profiling ephedrine/pseudoephedrine and methamphetamine synthesised from benzaldehyde, nitroethane and dimethyl carbonate

In previous work, a novel pathway for the synthesis of ephedrine/pseudoephedrine and methamphetamine using the precursors benzaldehyde, nitroethane and dimethyl carbonate was investigated, and an impurity profile presented. This paper presents chiral and stable isotope ratios of ephedrine/pseudoephedrine and methamphetamine synthesised by this pathway. Based on the chiral profile and the more negative δ13C (avg. -33.2‰) and more positive δ2H values, it is possible to distinguish ephedrine/pseudoephedrine and methamphetamine prepared from this pathway from those of "fully synthetic", "semi-synthetic" or "natural" origin. The more positive δ2H values of methamphetamine from this pathway allowed for differentiation from methamphetamine produced from phenyl-2-propanone. It was noted, however, that the use of stable isotope profiling would likely be limited when a benzaldehyde source having a negative δ2H value was used as a precursor. Furthermore, the stable isotope values alone could not be used to differentiate from methamphetamine prepared by the Akabori-Momotani reaction, highlighting the need for combination with impurity profiling.

Stable isotope composition of pesticides in commercial formulations: The ISOTOPEST database

By assessing the changes in stable isotope compositions within individual pesticide molecules, Compound Specific Isotope Analysis (CSIA) holds the potential to identify and differentiate sources and quantify pesticide degradation in the environment. However, the environmental application of pesticide CSIA is limited by the general lack of knowledge regarding the initial isotopic composition of active substances in commercially available formulations used by farmers. To address this limitation, we established a database aimed at cataloguing and disseminating isotopic signatures in commercial formulations to expand the use of pesticide CSIA. Our study involved the collection of 25 analytical standards and 120 commercial pesticide formulations from 23 manufacturers. Subsequently, 59 commercial formulations and 25 standards were extracted, and each of their active substance was analyzed for both δ13C (n = 84) and δ15N CSIA (n = 43). The extraction of pesticides did not cause significant isotope fractionation (Δ13C and Δ15N < 1‰). Incorporating existing literature data, stable carbon and nitrogen isotope signatures varied in a relatively narrow range among pesticide formulations for different pesticides (Δ13C and Δ15N < 10‰) and within different formulations for a single substance (Δ13C and Δ15N < 2‰). Overall, this suggests that pesticide CSIA is more suited for identifying pesticide transformation processes rather than differentiating pesticide sources. Moreover, an inter-laboratory comparison showed similar δ13C (Δ13C ≤ 1.2 ‰) for the targeted substances albeit varying GC-IRMS instruments. Insignificant carbon isotopic fractionation (Δ13C < 0.5‰) was observed after 4 years of storing the same pesticide formulations, confirming their viability for long-term storage at 4 °C and future inter-laboratory comparison exercises. Altogether, the ISOTOPEST database, in open access for public use and additional contributions, marks a significant advancement in establishing an environmentally relevant pesticide CSIA approach.

BITACORA: An isotopic database of modern human tissues (keratin, teeth) for Argentina

As a consequence of the recent history of Argentina related to crimes against humanity, the country has positioned itself as a leader on Forensic Anthropology in human rights contexts. To some extent it can even be argued that Forensic Genetics for human identification had its origins in human rights work in the early 1980s in Argentina. However, there are still hundreds of unidentified human remains recovered from the dictatorial regimes' crimes. Additionally, every year there are dozens of unidentified deceased buried in public cemeteries. Thus, there is an urgent need to adopt new techniques that could increase the biological profile of a person, and therefore increase the chances of positive identifications. One of such initiatives is the development of isotopic databases and models that can provide information on the population and region of origin of unidentified victims. We present the development of an isotopic database of modern human tissues named BITACORA (from its name in Spanish: Base de Información Isotópica de Tejidos Actuales Como Referencia Argentina). BITACORA holds isotopic data (δ18O, δ2H, δ13C, δ15N and δ34S values) from teeth (enamel and dentine) and keratin tissues (scalp hair, beard and fingernails) obtained from volunteers of known origin, as well as individual information of the donors (age, gender, biometrics, dietary preferences, and relocation history). BITACORA is associated with a tap water isotope database. Currently, we have 345 keratin, 273 teeth and 287 tap water samples gathered from across the country. We present preliminary analyses on the geographic distribution of these isotopic markers, and provide an overall discussion of the current status and future development of the databases.

Digital forensic intelligence for illicit drug analysis in forensic investigations

In forensic investigations, forensic intelligence is required for illicit drug profiling in order to allow police officers and law enforcements to recognize crime developments and adjust their actions. In the present paper, we propose a novel framework for Digital Forensic Drug Intelligence (DFDI) by fusing digital forensic and drug profiling data through intelligent cycles, where a targeted and iterative collection of evidence from diverse sources is a core step in the process of drug profiling. Drug profiling data combined with digital data from seized devices collected, examined, and analyzed will allow authorities to generate valuable information about illicit drug trafficking routes and manufacturing. Such data can be stored in seized illicit drug databases to build in an intelligent way, all findings, hypotheses and recommendations, allowing law enforcement to make decisions. Our framework will potentially provide a better understanding of profiling, trafficking and distribution of illicit drugs.

Forensic Mass Spectrometry: Scientific and Legal Precedents

Mass spectrometry has made profound contributions to the criminal justice system by providing an instrumental method of analysis that delivers exquisite analytical figures of merit for a wide variety of samples and analytes. Applications include the characterization of trace metal impurities in hair and glass to the identification of drugs, explosives, polymers, and ignitable liquids. This review describes major historical developments and, where possible, relates the developed capabilities to casework and legal precedents. This review also provides insight into how historical applications have evolved into, and out of, modern consensus standards. Unlike many pattern-based techniques and physical-matching methods, mass spectrometry has strong scientific foundations and a long history of successful applications that have made it one of the most reliable and respected sources of scientific evidence in criminal and civil cases. That said, in several appellate decisions in which mass spectrometric evidence was challenged but admitted, decisions sometimes still went against the mass spectrometric data anyway, which goes to show that mass spectrometric evidence is always just one piece of the larger legal puzzle.

Proteomics-Compatible Fourier Transform Isotopic Ratio Mass Spectrometry of Polypeptides

Measuring the relative abundances of heavy stable isotopes of the elements C, H, N, and O in proteins is of interest in environmental science, archeology, zoology, medicine, and other fields. The isotopic abundance measurements of the fine structure of immonium ions with ultrahigh resolution mass spectrometry obtained in gas-phase fragmentation of polypeptides have previously uncovered anomalous deuterium enrichment in (hydroxy)proline of bone collagen in marine mammals. Here, we provide a detailed description and validation of this approach and demonstrate per mil-range precision of isotopic ratio measurements in aliphatic residues from proteins and cell lysates. The analysis consists of proteomics-type experiment demanding sub-microgram amounts of a protein sample and providing concomitantly protein sequence data allowing one to verify sample purity and establish its identity. A novel software tool protein amino acid-resolved isotopic ratio mass spectrometry (PAIR-MS) is presented for extracting isotopic ratio data from the raw data files acquired on an Orbitrap mass spectrometer.

State-of-the-Art Analytical Approaches for Illicit Drug Profiling in Forensic Investigations

In forensic chemistry, when investigating seized illicit drugs, the profiling or chemical fingerprinting of drugs is considered fundamental. This involves the identification, quantitation and categorization of drug samples into groups, providing investigative leads such as a common or different origin of seized samples. Further goals of drug profiling include the elucidation of synthetic pathways, identification of adulterants and impurities, as well as identification of a drug's geographic origin, specifically for plant-derived exhibits. The aim of this state-of-art-review is to present the traditional and advanced analytical approaches commonly followed by forensic chemists worldwide for illicit drug profiling. We discussed numerous methodologies for the physical and chemical profiling of organic and inorganic impurities found in illicit drug. Applications of powerful spectroscopic and chromatographic tools for illicit drug profiling including isotope-Ratio mass spectrometry (IRMS), gas chromatography-mass spectrometry (GC-MS), gas chromatography-isotope ratio mass spectrometry (GC-IRMS), ultra-high-performance liquid chromatography (UHPLC), thin layer chromatography (TLC), liquid chromatography-mass spectrometry (LC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) were discussed. Altogether, the techniques covered in this paper to profile seized illicit drugs could aid forensic chemists in selecting and applying a suitable method to extract valuable profiling data.

Short-term exposure to soils and sludge induce changes to plastic morphology and 13C stable isotopic composition

There is concern about the buildup of plastic waste in soil, their degradation into microplastics, and their potential to interfere with the natural processing of soil organic carbon and other nutrient cycling processes. Here we used scanning electron microscopy (SEM) and ¹³C isotope ratio mass spectrometry to determine if precut consumer plastics comprised of either high density polyethylene (HDPE), a blend of linear low density polyethylene and low density polyethylene (L/LDPE), or polyethylene terephthalate (PETE) would degrade or transform during a short-term, 32 day, exposure to soil or sludge in laboratory microcosms. SEM confirmed morphological changes occurred to all plastics, but the attachment of biofilm and presence of microorganisms mostly favored PETE and HDPE surfaces. These observations support the idea that abiotic and/or biotic processes may degrade plastics in soil; however distinguishable and significant changes in mean stable isotopic values (Δδ¹³C) of ~0.2-0.7‰ were only observed for exposed PETE and HDPE. This indicates that each plastic's degradation in soil may be dependent on their physical and chemical properties, with L/LDPE being more resistant and less prone to degradation compared to the others, and less dependent on the environmental conditions or properties of the soil or sludge. Our experiments were short-term and while the mechanisms of degradation are not clear, the results provide strong motivation for further studies of plastic fate and processing in soil systems. Direct mechanistic studies using stable isotopic approaches in combination with other characterizations and techniques are clearly warranted and may lead to a significant enhancement in our present understanding of the interactions and dynamics of plastics in the soil environment.

Investigations on historical monuments' deterioration through chemical and isotopic analyses: an Italian case study

In this paper, we analysed the efflorescences present in the frescos of a monumental complex named S. Pietro a Corte situated in the historic centre of Salerno (Campania, Italy). The groundwater of the historic centre is fed by two important streams (the Rafastia and the Fusandola) that can be the sources of water penetration. The aims of this work are to (i) identify the stream that reaches the ancient frigidarium of S. Pietro a Corte and (ii) characterize the efflorescences on damaged frescos in terms of chemical nature and sources. In order to accomplish the first aim, the water of the Rafastia river (7 samples) and the water of the Fusandola river (7 samples) were analysed and compared with the water of a well of the Church (7 samples). The ionic chromatography measurements on the water samples allowed us to identify the Rafastia as the river that feeds the ancient frigidarium of S. Pietro a Corte. To investigate the nature and the origin of the efflorescences (our second aim), anionic chromatography analyses, X-ray diffraction measurements, and the isotopic determination of nitrogen were performed on the efflorescences (9 samples) and the salts recovered from the well (6 samples). Results of these analyses show that efflorescences are mainly made of potassium nitrate with a δ¹⁵N value of + 9.3 ± 0.2‰. Consequently, a plausible explanation for their formation could be the permeation of sewage water on the walls of the monumental complex.

Building an isoscape based on tooth enamel for human provenance estimation in Brazil

In this study, we present a correlation between δ¹⁸O_C values of carbonate in tooth enamel samples from the modern Brazilian population and the available δ¹⁸O_DW data for the meteoric water from the Global Network of Isotopes in Precipitation (GNIP). Tooth enamel from 119 Brazilian individuals from five different regions of the country were analyzed. The δ¹⁸O_C isoscape obtained is in good agreement with the isoscape based on regional meteoric and drinking water. The regression matrix obtained for the δ¹⁸O values of the carbonate tooth enamel and meteoric water was used to build an isoscape using the regression-kriging approach. Our data show that Brazil can be divided in two main regions with respect to the δ¹⁸O values of the carbonate tooth enamel: (1) the most easterly part of the northeast region, which is characterized by a warm and dry climate and (2) the remainder of the country, stretching from the Amazon rain forest to the more southernly regions. The data herein reported can be used for forensic purposes related to human identification.

Carbon and Nitrogen Isotopic Analysis of Morphine from Opium and Heroin Samples Originating in the Four Major Heroin Producing Regions

The forensic analysis of stable isotopes is a valuable tool to geo-source natural or semi-synthetic drugs such as cocaine and heroin. The present study describes a novel methodology to isolate morphine from opium for isotopic analysis. Furthermore, this isotopic data from regional sources is corroborated with morphine data obtained from seized heroin (de-acetylated to morphine) from the same regions. All five primary alkaloids of opium, namely morphine, codeine, thebaine, noscapine and papaverine, were quantified using high performance liquid chromatography with PDA before the preparative experiment to gather a complete major alkaloidal profile. Morphine fractions of authentic opium submissions from Mexico, South America, Southwest Asia, and Southeast Asia were isolated and collected using preparative high performance liquid chromatography, and the collected morphine samples were subsequently analyzed by isotope ratio mass spectrometry. Carbon and nitrogen isotope data are presented. The data demonstrates that nitrogen ratios are capable of differentiating samples from Mexico and South America while carbon ratios are able to distinguish Southwest Asian samples from other source regions. Analogous results have routinely been observed (as part of Heroin Signature Program analysis) for morphine obtained from de-acetylated authentic heroin samples from the same source regions. The results suggest that the poppy growing region has a greater influence on the carbon and nitrogen isotope values than the heroin manufacturing processes employed. When utilized in conjunction with existing signature methodologies, carbon and nitrogen isotope ratio data can enhance the ability to geo-source heroin.

Chemotyping of Δ8-THC-Containing e-Liquids Analyzed during the 2019-2020 New York State EVALI Investigation

The investigation of the 2019-2020 E-cigarette or Vaping Product Use-Associated Lung Injury (EVALI) outbreak in New York State provided a unique opportunity to examine the formulations and chemical components found in clandestine cannabis-containing e-liquids. In this EVALI investigation, it was determined that an unusually high proportion (16%) of the cannabis e-liquids analyzed contained significant levels of Δ8-tetrahydrocannabinol (Δ8-THC). Although not thought to be the causative agent in the outbreak, the manufacturing origin of vaping e-liquids containing large concentrations of Δ8-THC was of great interest, since high Δ8-THC concentrations are not observed in the extracts of common cannabis strains. A principal component analysis of multiple cannabinoid concentrations revealed clusters of similar or identical Δ8-THC-containing products. This technique may be useful in identifying common manufacturing sources in this and future investigations. Several possible manufacturing methods to enrich Δ8-THC appear in literature and are discussed based on their likelihood as sources of this cannabinoid in these samples from the EVALI investigation. The presence of high levels of Δ8-THC in numerous illicit vaping products may implicate cannabidiol, which is readily available at low cost, as its synthetic precursor.

Source Attribution of the Chemical Warfare Agent Soman Using Position-Specific Isotope Analysis by 2H NMR Spectroscopy: From Precursor to Degradation Product

Position-specific isotope analysis (PSIA) by NMR spectroscopy is a technique that provides quantitative isotopic values for every site—a so-called isotopic fingerprint—of a compound of interest. The isotopic fingerprint can be used to link samples with a common origin or to attribute a synthetic chemical to its precursor source. Despite PSIA by NMR being a powerful tool in chemical forensics, it has not yet been applied on chemical warfare agents (CWAs). In this study, different batches of the CWA Soman were synthesized from three distinctive pinacolyl alcohols (PinOHs). Prior to NMR analysis, the Soman samples were hydrolyzed to the less toxic pinacolyl methylphosphonate (PMP), which is a common degradation product. The PinOHs and PMPs were applied to PSIA by ²H NMR experiments to measure the isotopic distribution of naturally abundant ²H within the pinacolyl moiety. By normalizing the ²H NMR peak areas, we show that the different PinOHs have unique intramolecular isotopic distributions. This normalization method makes the study independent of references and sample concentration. We also demonstrate, for the first time, that the isotopic fingerprint retrieved from PSIA by NMR remains stable during the production and degradation of the CWA. By comparing the intramolecular isotopic profiles of the precursor PinOH with the degradation product PMP, it is possible to attribute them to each other.

[Recent advances in stable isotope ratio analysis of common explosives]

炸药的深度比对与溯源对于爆炸案事件的侦破具有重大意义,以不同地域来源的原料或不同生产工艺生产的炸药,其组成元素的稳定同位素比值具有差异,因而稳定同位素比值可作为炸药深度比对与溯源的重要指标。稳定同位素比值质谱法(IRMS)作为一种高精度的稳定同位素比值测量手段,已逐渐发展成熟,与元素分析仪、气相色谱仪、液相色谱仪等仪器联用,在食品安全、环境保护、法庭科学等领域应用广泛。IRMS在炸药比对与溯源上亦发挥了重要作用,自1975年IRMS被应用于区分不同国家生产的三硝基甲苯(TNT)以来,IRMS已成功用于多种炸药的分析。但目前尚未见有文献系统地总结常见炸药的稳定同位素比值分析研究进展。该文介绍了稳定同位素比值分析的相关原理、仪器组成及特点,分别总结了硝酸铵、黑火药、TNT、太恩、黑索金等常见炸药的稳定同位素比值分析方法,汇总了文献报道的不同国家生产的硝酸铵、黑火药、TNT等炸药的稳定同位素比值。文章就不同炸药的稳定同位素比值差异、炸药生产、存储过程中相关因素对同位素比值的影响,爆炸前后稳定同位素比值的变化情况等内容进行了分析。本文还指出了目前炸药的稳定同位素比值分析研究中存在的问题,对可能的解决办法进行了讨论,对未来的发展方向提出了建议。

MASS SPECTROMETRY-BASED TECHNIQUES FOR DIRECT QUANTIFICATION OF HIGH IONIZATION ENERGY ELEMENTS IN SOLID MATERIALS-CHALLENGES AND PERSPECTIVES

The determination of nonmetals, first of all, the most electronegative ones-nitrogen, oxygen, fluorine, chlorine, and bromine, poses the highest challenge for element analysis. These elements are characterized by high reactivity, volatility, high ionization energy, and the absence of intensive spectral lines in the optical spectral range. Conventional techniques of their quantification include considerable "wet chemistry" stages so the application of these techniques for the solid sample is highly laborious and prone to uncontrollable uncertainties. Additionally, current development in material science and other areas requires the quantification of the elements at lower levels with good sensitivity. Owing to their robustness and flexibility, mass spectrometry techniques provide vast possibilities for the quantification, spatial and isotopic analysis, including the solutions for direct analysis of solids. The current review focuses on the application of major mass spectrometric techniques for the quantification of N, O, F, Cl, and Br in solid samples. The following techniques are mainly considered: thermal ionization mass spectrometry (TIMS), isotope-ratio MS (IRMS), secondary ion MS (SIMS), inductively coupled plasma MS (ICP-MS), and glow discharge MS (GDMS); as the most accessible and widely applied for the purpose. General ionization issues, advantages, limitations, and novel methodological solutions are discussed. © 2020 John Wiley & Sons Ltd.

OpiumPlex is a novel microsatellite system for profiling opium poppy (Papaver somniferum L.)

Opium poppy (Papaver somniferum L.) is a versatile plant exploited by the pharmaceutical and food industries. Unfortunately, it is also infamously known as a source of highly addictive narcotics, primarily heroin. Drug abuse has devastating consequences for users and also has many direct or indirect negative impacts on human society as a whole. Therefore, developing a molecular genetic tool for the individualization of opium poppy, raw opium or heroin samples could help in the fight against the drug trade by retrieving more information about the source of narcotics and linking isolated criminal cases. Bioinformatic analysis provided insight into the distribution, density and other characteristics of roughly 150 thousand microsatellite loci within the poppy genome and indicated underrepresentation of microsatellites with the desired attributes. Despite this fact, 27 polymorphic STR markers, divided into three multiplexed assays, were developed in this work. Internal validation confirmed species-specific amplification, showed that the optimal amount of DNA is within the range of 0.625-1.25 ng per reaction, and indicate relatively well balanced assays according to the metrics used. Moreover, the stutter ratio (mean + 3 SD 2.28-15.59%) and allele-specific stutters were described. The analysis of 187 individual samples led to the identification of 158 alleles in total, with a mean of 5.85 alleles and a range of 3-14 alleles per locus. Most of the alleles (151) were sequenced by the Sanger method, which enabled us to propose standardized nomenclature and create three allelic ladders. The OpiumPlex system discriminates most of the varieties from each other and pharmaceutical varieties from the others (culinary, dual and ornamental).

Preliminary stable isotope analyses for propellant discrimination in shotshells

RATIONALE

This study aimed to develop methods to determine the identity and trace the origin of propellants used in shotshells. Specifically, the use of organic component and stable isotope analysis techniques, such as bulk stable isotope analysis (BSIA) and compound-specific isotope analysis (CSIA) techniques, for the study of shotshell propellants was investigated.

METHODS

Nine samples of shotshell propellants from different manufacturing countries and brands were analyzed for explosive and additive components by gas chromatography/mass spectrometry and thin-layer chromatography. BSIA of the propellants was achieved using elemental analysis/isotope ratio mass spectrometry without a pretreatment process. For the CSIA of nitroglycerin, double-base powder propellants were extracted with ether, and the isotope ratios of carbon and nitrogen were measured by gas chromatography/isotope ratio mass spectrometry.

RESULTS

Nine samples drawn from seven brands in four countries were classified into five groups by organic component analysis, while eight classification groups were identified by BSIA. Thus, two samples could not be distinguished from each other by either BSIA or organic component analysis. Subsequently, with the use of results obtained with CSIA for nitroglycerin, all the samples could be classified into different groups. These findings suggest that the nine propellant samples were all composed of different ingredients or raw materials from different sources.

CONCLUSIONS

Stable isotope ratio analyses were performed for propellant discrimination. The combined BSIA, CSIA and organic component analysis techniques were able to successfully distinguish the nine shotshell propellants from seven brands sourced from four different countries, and the results suggested that the samples contained different ingredients or raw materials from different sources. We therefore can conclude that reliable results can be obtained using combined isotope analysis methods such as CSIA and BSIA for origin tracing and identity determination.

Microplastics in the Aquatic Environment: Occurrence, Persistence, Analysis, and Human Exposure

Microplastics (MP) have recently been considered as emerging contaminants in the water environment. In the last number of years, the number of studies on MP has grown quickly due to the increasing consciousness of the potential risks for human health related to MP exposure. The present review article discusses scientific literature regarding MP occurrence and accumulation on the aquatic compartment (river, lake, wastewater, seafood), the analytical methods used to assess their concentration, their fate and transport to humans, and delineates the urgent areas for future research. To better analogize literature data regarding MP occurrence in the aquatic compartment we subdivided papers based on sampling, analytical methods, and concentration units with the aim to help the reader identify the similarities and differences of the considered research papers, thus making the comparison of literature data easier and the individuation of the most relevant articles for the reader’s interests faster. Furthermore, we argued about several ways for MP transport to humans, highlighting some gaps in analytical methods based on the reviewed publications. We suggest improving studies on developing standardized protocols to collect, process, and analyze samples.

Intramolecular non-covalent isotope effects at natural abundance associated with the migration of paracetamol in solid matrices during liquid chromatography

Position-specific isotope analysis by Nuclear Magnetic Resonance spectrometry was employed to study the ¹³C intramolecular isotopic fractionation associated with the migration of organic substrates through different stationary phases chromatography columns. Liquid chromatography is often used to isolate compounds prior to their isotope analysis and this purification step potentially alters the isotopic composition of target compounds introducing a bias in the later measured data. Moreover, results from liquid chromatography can yield the sorption parameters needed in reactive transport models that predict the transport and fate of organic contaminants to in the environment. The aim of this study was to use intramolecular isotope analysis to study both ¹³C and ¹⁵N isotope effects associated with the elution of paracetamol (acetaminophen) through different stationary phases and to compare them to effects observed previously for vanillin. Results showed very different intramolecular isotope fractionation profiles depending on the chemical structure of the stationary phase. The data also demonstrate that both the amplitude and the distribution of measured isotope effects depend on the nature of the non-covalent interactions involved in the migration process. Results provided by theoretical calculation performed during this study also confirmed the direct link between observed intramolecular isotope fractionation and the nature of involved intermolecular interactions. It is concluded that the nature of the stationary phase through which the substrate passes has a major impact on the intramolecular isotopic composition of organic compounds isolated by chromatography methods..

A machine learning toolkit for genetic engineering attribution to facilitate biosecurity

The promise of biotechnology is tempered by its potential for accidental or deliberate misuse. Reliably identifying telltale signatures characteristic to different genetic designers, termed 'genetic engineering attribution', would deter misuse, yet is still considered unsolved. Here, we show that recurrent neural networks trained on DNA motifs and basic phenotype data can reach 70% attribution accuracy in distinguishing between over 1,300 labs. To make these models usable in practice, we introduce a framework for weighing predictions against other investigative evidence using calibration, and bring our model to within 1.6% of perfect calibration. Additionally, we demonstrate that simple models can accurately predict both the nation-state-of-origin and ancestor labs, forming the foundation of an integrated attribution toolkit which should promote responsible innovation and international security alike.

The Use of Stable Isotope Ratio Analysis to Trace European Sea Bass (D. labrax) Originating from Different Farming Systems

Simple Summary

European sea bass is one of the most economically important fish species in the Mediterranean area. The potential effects of farming systems on the final quality of this product and the recent popular demand for labels to certify the animal rearing origin, which is increasingly used as a marketing tool, have raised the use of analytical techniques that make it possible to differentiate this fish product according to the rearing farming system and authenticate their geographical origin. The aim of this study was to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) and geographic origins (different locations scattered throughout Italy). The results of this study showed the viability of δ¹³C and δ¹⁵N to discriminate cultured sea bass from different farming systems (extensive vs. intensive) reared at different geographical sites in Italy. Meanwhile, the measurement of δ¹⁸O and δ²H made it possible to distinguish the geographical origin of the sea bass farmed extensively and intensively (in cages).

Abstract

This study aimed to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems and geographic origins. Dicentrarchus labrax of commercial size from three different rearing systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) were collected at the trading period (autumn–winter). For each farming type, different locations spread over Italy were monitored. Once the fish were harvested, the muscle and feed were sampled. For both muscle and feed, δ¹³C and δ¹⁵N were measured by continuous flow elemental analyzer isotope ratio mass spectrometry (CF-EA-IRMS) with the goal of discriminating samples based on the rearing system. Additional δ²H and δ¹⁸O measurements of fish samples were performed by continuous flow total combustion elemental analyzer isotope ratio mass spectrometry (CF-TC/EA-IRMS) to track the geographical origin. The measurements of δ¹³C and δ¹⁵N made it possible to discriminate cultured sea bass from different farming systems (extensive vs. intensive) reared at different geographical sites in Italy. Additional information was obtained from δ¹⁸O and δ²H, which enabled the geographical areas of origin of the sea bass farmed extensively and intensively (in cages) to be distinguished.

Natural abundance carbon isotope ratio analysis and its application in the study of diet and metabolism

Due to differences in carbon assimilation pathways between plants, there are subtle but distinct variations in the carbon isotope ratios of foods and animal products throughout the food supply. Although it is well understood that the carbon isotope ratio composition of the diet influences that of the consumers' tissues, the application of natural abundance carbon isotope ratio analysis in nutrition has long been underappreciated. Over the past decade, however, several studies have investigated the utility of carbon isotope ratio analysis for evaluation of nutritional biomarker status, primarily focusing on its application as an objective indicator of sugar and animal protein intake. More recently, research investigating the application of natural abundance measurements has been extended to study fatty acid metabolism and has yielded encouraging results. Collectively, data from large-scale observational studies and experimental animal studies highlight the potential for carbon isotope ratio analysis as an additional and effective tool to study diet and metabolism. The purpose of this review is to provide an overview of natural abundance carbon isotope ratio analysis, its application to studying nutrition, and an update of the research in the field.

Investigations into the source attribution of party sparklers using trace elemental analysis and chemometrics

In Australia, party sparklers are commonly used to initiate or prepare inorganic based homemade explosives (HMEs) as they are the most easily accessible and inexpensive pyrotechnic available on the market. As sparkler residue would be encountered in cases involving these types of devices, the characterisation and source determination of the residue would be beneficial within a forensic investigation. The aim of this study is to demonstrate the potential of using trace elemental profiling coupled with chemometric and other statistical techniques to link a variety of different sparklers to their origin. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine the concentration of 50 elements in 48 pre-blast sparkler samples from eight sparkler brands/classes available in Australia. Extracting ground-up sparkler residue in 10% nitric acid for 24 hours was found to give the most reliable quantification. The collected data were analysed using Principal Component Analysis (PCA) to visualise the distribution of the sample data and explore whether the sparkler samples could be classified into their respective brands. ANOVA based feature selection was used to remove elements that did not largely contribute to the separation between classes. This resulted in the development of a 7-elemental profile, consisting of V, Co, Ni, Sr, Sn, Sb, W, which could be used to correctly classify the samples into eight distinct groups. Linear Discriminant Analysis (LDA) was subsequently used to construct a discriminant model using four out of six samples from each class. The model successfully classified 100% of the samples to their correct sparkler brand. The model also correctly matched 100% of the remaining samples to the correct class. This demonstrates the potential of using trace elemental analysis and chemometrics to correctly identify and discriminate between party sparklers.

A review of the newly identified impurity profiles in methamphetamine seizures

Forensic intelligence of synthetic illicit drugs suffers a problem of continuous introduction of new synthetic methods, modification of the existing routes of manufacture, and adulterations practiced by criminal networks. Impurity profiling has been indispensable in methamphetamine intelligence based on precursors, synthetic routes, and chemical modifications during trafficking. Law enforcement authorities maintain the credibility and integrity of intelligence information through constant monitoring of the chemical signatures in the illicit drug market.

Changes in the synthetic pattern result in new impurity profiles that are important in keeping valuable intelligence information on clandestine laboratories, new synthetic routes, trafficking patterns, and geographical sources of illicit Methamphetamine.

This review presents a critical analysis of the methamphetamine impurity profiles and more specifically, profiling based on impurity profiles from Leuckart, Reductive amination, Moscow, Emde, Nagai, Birch, Moscow route; a recent nitrostyrene route and stable isotope signatures. It also highlights the discrimination of ephedrine from pseudoephedrine sources and the emerging methamphetamine profiling based on stable isotopes.

A coherent method for combined stable magnesium and radiogenic strontium isotope analyses in carbonates (with application to geological reference materials SARM 40, SARM 43, SRM 88A, SRM 1B)

We undertook ⁸⁷Sr/⁸⁶Sr analyses for a range of carbonate bearing geological reference materials, and combined these with δ²⁶Mg for a subset of samples. Following chemical purification in a series of chromatographic extractions, isotope ratios were measured by Multi-Collector-ICP-MS using a Plasma II (Nu instruments, Wrexham, UK). To validate efficient sample digestion procedures of carbonate fractions, total samples were treated with either 3 mol l^-1 HNO₃ and 0.5 mol l^-1 HCl, respectively. Results of both leaching procedures are identical within reproducibility. Reference values for SRM 88A (formerly NBS 88A), SRM 1B (formerly NBS 1B), SARM 40, SARM 43, JDo-1, JLs-1, and San Carlos olivine range from 0.70292 to 0.73724 in ⁸⁷Sr/⁸⁶Sr and from -2.80 to -0.41 ‰ for δ²⁶Mg, respectively. This set of geological reference materials can be used for sedimentary rock material with different carbonate mineral and matrix composition as quality control measurements of combined stable Mg and radiogenic Sr isotope analyses.•We present a protocol that facilitates the chemical separation of Mg and Sr in carbonate bearing geological reference materials including ⁸⁷Sr/⁸⁶Sr and δ²⁶Mg of certified reference materials.

Deuterium analysis by inductively coupled plasma mass spectrometry using polyatomic species: An experimental study supported by plasma chemistry modeling

A new analytical method is proposed for the determination of deuterium (D) by ICP-MS. The method is based on the use of the signal from hydrogen-containing polyatomic ions formed in the inductively coupled plasma. Prior to analytical experiments, a theoretical study was performed to assess the concentration of polyatomic species present in an equilibrium Ar-O-D-H plasma, as a function of temperature and stoichiometric composition. It was established that the highest sensitivity and linearity measurement of D concentration in a wide range can be achieved by monitoring the ions of D₂ and ArD, at masses 4 and 42, respectively. Results of the calculations are in good agreement with the experiments. Signal stability, spectral interferences, as well as the effect of plasma parameters were also assessed. Under optimized conditions, the limit of detection (LOD) was found to be 3 ppm atom fraction for deuterium when measured as ArD (in calcium and potassium free water), or 78 ppm when measured as D₂. The achieved LOD values and the 4 to 5 orders of magnitude dynamic range easily allow the measurement of deuterium concentrations at around or above the natural level, up to nearly 100% (or 1 Mio ppm) in a standard quadrupole ICP-MS instrument. An even better performance is expected from the method in high resolution ICP-MS instruments equipped with low dead volume sample introduction systems.

Capillary Vibrating Sharp-Edge Spray Ionization (cVSSI) for Voltage-Free Liquid Chromatography-Mass Spectrometry

Here, we report a continuous flow-based ionization method, capillary vibrating sharp-edge spray ionization (cVSSI), that nebulizes liquid sample directly at the outlet of a capillary without using high-speed nebulization gas or a high electrical field. cVSSI is built upon the recently reported VSSI principle which nebulizes bulk liquid using vibrating sharp-edges. By attaching a short piece of fused silica capillary on top of the vibrating glass slide in VSSI, liquid is nebulized at the outlet of the capillary as the result of the vibration. Utilizing standard 360-μm OD/100-μm ID capillary, cVSSI works with a wide range of flow rates from 1 μL/min to 1 mL/min. The power consumption is as low as 130 mW. ESI-like MS spectra are obtained for small molecules, peptides, and proteins. Five orders of magnitude linear response for acetaminophen solution is achieved with a limit of detection (LOD) of 3 nM. cVSSI is also demonstrated to be compatible with LC-MS analysis. Two LC-MS applications are demonstrated with cVSSI: (1) separation and detection of a mixture of small molecules and (2) bottom-up proteomics using a protein digest. A mixture of nine common metabolites was appropriately separated and detected using LC-cVSSI-MS. In the bottom-up experiment, 78 peptides were detected using LC-cVSSI-MS/MS with a protein coverage of 100% for cytochrome c, which is comparable with the coverage obtained using LC-ESI-MS. cVSSI offers a means of interfacing LC or other continuous flow-based applications to mass spectrometers with the salient features of voltage-free, flexibility, small footprint, and low power consumption.

Recent applications of isotope analysis to forensic anthropology

Isotope analysis has become an increasingly valuable tool in forensic anthropology casework over the past decade. Modern-day isotopic investigations on human remains have integrated the use of multi-isotope profiles (e.g. C, N, O, H, S, Sr, and Pb) as well as isotopic landscapes (“isoscapes”) from multiple body tissues (e.g. teeth, bone, hair, and nails) to predict possible region-of-origin of unidentified human remains. Together, data from various isotope analyses provide additional lines of evidence for human identification, including a decedent’s possible region-of-birth, long-term adult residence, recent travel history, and dietary choices. Here, we present the basic principles of isotope analysis and provide a brief overview of instrumentation, analytical standards, sample selection, and sample quality measures. Finally, we present case studies that reflect the diverse applications of isotope analysis to the medicolegal system before describing some future research directions. As shown herein, isotope analysis is a flexible and powerful geolocation tool that can provide new investigative leads for unidentified human remains cases.

Isotopic determination with molecular emission using laser-induced breakdown spectroscopy and laser-induced radical fluorescence

Molecular emission can be used for isotopic analysis in laser-induced breakdown spectroscopy (LIBS) due to its large isotopic shift. However, spectral weakness and interference have become the main flaws in molecular isotopic analysis, causing deterioration of quantitative accuracy and sensitivity. Here, to overcome these problems, laser-induced radical fluorescence (LIRF) was applied to enhance the molecular spectra and eliminate the spectral interference. The root mean square errors of cross validation (RMSECVs) of boron and carbon isotopes (¹¹BO, ¹⁰BO, ¹²CN, and ¹³CN) improved to 2.632, 5.721, 5.990, and 1.543 at.%, as compared with 16.96, 35.79, 57.10, and 13.89 at.%, respectively, obtained in the case without LIRF. The limits of detection (LoDs) of ¹¹BO, ¹⁰BO, ¹²CN, and ¹³CN were 0.9858, 0.8470, 1.606, and 1.193 at.%, respectively. This work demonstrates the feasibility of LIBS-LIRF to achieve isotopic determination with high accuracy and sensitivity.

Research on Differential Metabolites in Distinction of Rice (Oryza sativa L.) Origin Based on GC-MS

The analytical method for the metabolomics of the 60 rice seeds from two main rice origins in Heilongjiang Province was developed based on gas chromatography coupled with mass spectrum. The specific differential metabolites between two rice origins were identified, and the distinguish of the two main origins was illustrated by using the R software platform with XCMS software package for gas chromatography coupled with mass spectrum data processing, combined with multivariate statistical analysis software. The result indicated that the 173 peaks were detected, and 54 of which were structurally identified, covering amino acids, aliphatic acid, sugar, polyols, and so on. By comparing the data of Wuchang and Jiansanjiang origins, it was found that there were 9 special metabolites in Wuchang origin and 8 special metabolites in Jiansanjiang origin. The 10 differential metabolites with significant changes (P<0.05, VIP ≥ 1) were filtrated. It is indicated that the differential metabolites of rice carry information of their origin and there are the differences in the metabolites of rice in two main origins. The proposed method is expected to be useful for the metabolomic researches of rice.

Background survey of polyethylene in the Australian Capital Territory - A demonstration of variability in isotopic abundance values and their application to forensic casework

Plastics including adhesive tapes, cable ties, and packaging are common evidence types encountered in forensic investigations and casework. Traditional examination techniques such as Fourier Transform Infrared (FTIR) spectroscopy lack specificity and are unable to discern differences within the same polymer structures leaving the analyst with a generic identification. High quality manufacturing methods further amplify the limitations in detecting variability between samples. Isotope Ratio Mass Spectrometry (IRMS) has been shown to be a valuable technique in further discriminating plastics. Discrimination is achieved by analysing the relative abundances of stable isotopes within a sample, with differences detected in isotope ratios possibly attributed to the source of raw materials and fractionation during the manufacturing process. A survey of cling wraps and re-sealable zipper storage bags collected in the Australian Capital Territory was undertaken to assess the variability in carbon and hydrogen isotope ratios of different brands and samples. The results of this research are discussed, particularly with respect to within and between brand trends, and a case study is presented as an example of the value of including IRMS in a casework context.

Creating a 3D microbial and chemical snapshot of a human habitat

One of the goals of forensic science is to identify individuals and their lifestyle by analyzing the trace signatures left behind in built environments. Here, microbiome and metabolomic methods were used to see how its occupants used an office and to also gain insights into the lifestyle characteristics such as diet, medications, and personal care products of the occupants. 3D molecular cartography, a molecular visualization technology, was used in combination with mass spectrometry and microbial inventories to highlight human-environmental interactions. Molecular signatures were correlated with the individuals as well as their interactions with this indoor environment. There are person-specific chemical and microbial signatures associated with this environment that directly relate who had touched objects such as computers, computer mice, cell phones, desk phone, table or desks. By combining molecular and microbial investigation forensic strategies, this study offers novel insights to investigators who value the reconstructing of human lifestyle and characterization of human environmental interaction.

Infrared spectroscopy and spectroscopic imaging in forensic science

Infrared spectroscopy and spectroscopic imaging, are robust, label free and inherently non-destructive methods with a high chemical specificity and sensitivity that are frequently employed in forensic science research and practices. This review aims to discuss the applications and recent developments of these methodologies in this field. Furthermore, the use of recently emerged Fourier transform infrared (FT-IR) spectroscopic imaging in transmission, external reflection and Attenuated Total Reflection (ATR) modes are summarised with relevance and potential for forensic science applications. This spectroscopic imaging approach provides the opportunity to obtain the chemical composition of fingermarks and information about possible contaminants deposited at a crime scene. Research that demonstrates the great potential of these techniques for analysis of fingerprint residues, explosive materials and counterfeit drugs will be reviewed. The implications of this research for the examination of different materials are considered, along with an outlook of possible future research avenues for the application of vibrational spectroscopic methods to the analysis of forensic samples.

Deuterium- and Tritium-Labelled Compounds: Applications in the Life Sciences

Hydrogen isotopes are unique tools for identifying and understanding biological and chemical processes. Hydrogen isotope labelling allows for the traceless and direct incorporation of an additional mass or radioactive tag into an organic molecule with almost no changes in its chemical structure, physical properties, or biological activity. Using deuterium-labelled isotopologues to study the unique mass-spectrometric patterns generated from mixtures of biologically relevant molecules drastically simplifies analysis. Such methods are now providing unprecedented levels of insight in a wide and continuously growing range of applications in the life sciences and beyond. Tritium (³ H), in particular, has seen an increase in utilization, especially in pharmaceutical drug discovery. The efforts and costs associated with the synthesis of labelled compounds are more than compensated for by the enhanced molecular sensitivity during analysis and the high reliability of the data obtained. In this Review, advances in the application of hydrogen isotopes in the life sciences are described.

Carbon and hydrogen isotopic compositions of n-alkanes as a tool in petroleum exploration

Compound-specific isotope analysis (CSIA) of individual organic compounds is a powerful but underutilized tool in petroleum exploration. When integrated with other organic geochemical methodologies it can provide evidence of fluid histories including source, maturity, charge history and reservoir processes that can support field development planning and exploration efforts. The purpose of this chapter is to provide a review of the methodologies used for generating carbon and hydrogen isotope data for mid- and high-molecular-weight n-alkanes.

We discuss the factors that control stable carbon and hydrogen isotope compositions of n-alkanes and related compounds in sedimentary and petroleum systems and review current and future applications of this methodology for petroleum exploration. We discuss basin-specific case studies that demonstrate the usefulness of CSIA either when addressing particular aspects of petroleum exploration (e.g. charge evaluation, source rock–oil correlation, and investigation of maturity and in-reservoir processes) or when this technique is used to corroborate interpretations from integrated petroleum systems analysis, providing unique insights which may not be revealed when using other methods. CSIA of n-alkanes and related n-alkyl structures can provide independent data to strengthen petroleum systems concepts from generation and expulsion of fluids from source rock, to charge history, connectivity, and in-reservoir processes.

Proposed Confidence Scale and ID Score in the Identification of Known-Unknown Compounds Using High Resolution MS Data

High-resolution (HR) MS instruments recording HR-full scan allow analysts to go further beyond pre-acquisition choices. Untargeted acquisition can reveal unexpected compounds or concentrations and can be performed for preliminary diagnosis attempt. Then, revealed compounds will have to be identified for interpretations. Whereas the need of reference standards is mandatory to confirm identification, the diverse information collected from HRMS allows identifying unknown compounds with relatively high degree of confidence without reference standards injected in the same analytical sequence. However, there is a necessity to evaluate the degree of confidence in putative identifications, possibly before further targeted analyses. This is why a confidence scale and a score in the identification of (non-peptidic) known-unknown, defined as compounds with entries in database, is proposed for (LC-) HRMS data. The scale is based on two representative documents edited by the European Commission (2007/657/EC) and the Metabolomics Standard Initiative (MSI), in an attempt to build a bridge between the communities of metabolomics and screening labs. With this confidence scale, an identification (ID) score is determined as [a number, a letter, and a number] (e.g., 2D3), from the following three criteria: I, a General Identification Category (1, confirmed, 2, putatively identified, 3, annotated compounds/classes, and 4, unknown); II, a Chromatography Class based on the relative retention time (from the narrowest tolerance, A, to no chromatographic references, D); and III, an Identification Point Level (1, very high, 2, high, and 3, normal level) based on the number of identification points collected. Three putative identification examples of known-unknown will be presented. Graphical Abstract ᅟ.

Identification of ANFO: Use of luminescent taggants in post-blast residues

This work describes the incorporation of luminescent taggants in cartridges of ammonium nitrate-fuel oil (ANFO) to allow easy identification and collection of post-blast residues. Metal-Organic Frameworks taggants proved to be appropriate for explosive marking when ANFO proportions were above 3.0wt.%. Lanthanide-based light emission enabled in situ retrieval of explosive residues as well as chemical identification, allowing the creation of a coding system using Energy Dispersive Spectroscopy (EDS). The proposed method will accelerate laboratory analysis and support forensic investigations, connecting evidence to suspects and/or to the explosive origin.