Role of five synthetic reaction conditions on the stable isotopic composition of 3,4-methylenedioxymethamphetamine.

The identification of links between seizures of illicit 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") has been a global target of law enforcement agencies in recent years. Previous work has shown that, when the reaction conditions are carefully repeated from batch to batch, stable isotope ratios allow the discrimination of MDMA.HCl batches according to synthetic route used for manufacture. In this study, the effects of altering five reaction conditions relating to the Pt/H(2) reductive amination synthesis were, for the first time, systematically investigated using a two level, five factor factorial design. Results indicate that the delta(2)H values of MDMA.HCl are affected by the length of imine stir time, and the delta(15)N values are affected by the degree of excess methylamine employed. Furthermore, the delta(13)C and delta(18)O values have been shown to be affected by the efficiency of the reaction, despite the similarity in carbon and oxygen composition of the starting material and product molecules. In addition to being of theoretical importance in this field of analytical science overall, this work is essential in order to more fully contextualize the interpretation of IRMS data which may be used as potential forensic evidence.

An initial evaluation of stable isotopic characterisation of post-blast plastic debris from improvised explosive devices.

A number of two-way radios, similar to those which have been employed to initiate Improvised Explosive Devices (IEDs), were acquired from a commercial supplier and grouped into four pairs. Samples of plastic material were collected from five distinct regions of each radio and analysed by Infrared and Raman spectroscopy to identify the nature of the material. One radio of each pair was then subjected to detonation with a commercially available plastic explosive. The combination of radio and explosive was considered to be representative of the components of an IED. Following detonation, fragments were recovered and, where possible, identified as specific sampling points of the radio. A combination of delta2H and delta13C stable isotopic analysis of material from each of the five sampling points was found to provide a pattern which was characteristic of a given radio and provided a means to associate pairs of radios. When few fragments were recovered, no positive association could be made between the fragments and the paired, undamaged radio. This was attributed, in part, to manufacturing variation in the radios. However, when three or more post-blast fragments were recovered it was possible to associate these with the paired, undamaged radio with a high degree of certainty.

Results of four inter-laboratory comparisons provided by the Forensic Isotope Ratio Mass Spectrometry (FIRMS) network.

Between 2004 and 2008 the Forensic Isotope Ratio Mass Spectrometry (FIRMS) network organised four Inter-Laboratory Camparison excercises with the aim of harmonising and validating isotopic measurements to be used for forensic applications. The samples distributed comprised materials of potential forensic interest such as packaging and pharmaceuticals to be analysed for delta2H, delta13C, delta15N and delta18O composition. As many as 30 international laboratories participated in these comparisons. Results have shown overall improvements for both within- and inter-laboratory reproducibility with respect to delta13C and delta15N measurements. Only a small number of laboratories returned results for delta2H and delta18O analysis and these results highlighted a need for improvement in the reproducibility of these measurements and a need to address the exchange of hydrogen between samples and ambient moisture. Results also highlighted the importance of sample preparation procedures and the need to standardise both these procedures and calibration against Standard Reference Materials. Future Inter-laboratory Comparison exercises will assess the suitability of laboratories to submit data to national and international databases similar to those currently operated for fingerprints, DNA etc.

Stable isotope ratio mass spectrometry and physical comparison for the forensic examination of grip-seal plastic bags.

Plastic bags are frequently used to package drugs, explosives and other contraband. There exists, therefore, a requirement in forensic casework to compare bags found at different locations. This is currently achieved almost exclusively by the use of physical comparisons such as birefringence patterns. This paper discusses some of the advantages and shortcomings of this approach, and presents stable isotope ratio mass spectrometry (IRMS) as a supplementary tool for effecting comparisons of this nature. Carbon and hydrogen isotopic data are presented for sixteen grip-seal plastic bags from a wide range of sources, in order to demonstrate the range of values which is likely to be encountered. Both isotopic and physical comparison (specifically birefringence) techniques are then applied to the analysis of rolls of bags from different manufacturing lots from a leading manufacturer. Both approaches are able to associate bags from a common production batch. IRMS can be applied to small fragments which are not amenable to physical comparisons, and is able to discriminate bags which could be confused using birefringence patterns alone. Similarly, in certain cases birefringence patterns discriminate bags with similar isotopic compositions. The two approaches are therefore complementary. When more than one isotopically distinct region exists within a bag (e.g. the grip-seal is distinct from the body) the ability to discriminate and associate bags is greatly increased.

Supported liquid-liquid extraction of the active ingredient (3,4-methylenedioxymethylamphetamine) from ecstasy tablets for isotopic analysis.

A method was developed for the isolation of 3,4-methylenedioxymethylamphetamine (MDMA) and other active ingredients from illicit ecstasy tablets. The method employed supported liquid extraction (SLE) with cartridges containing a modified form of diatomaceous earth. The method developed was simple and robust and the extract could be analysed directly, by GC-MS, to identify ingredients and reduced in volume for isotope ratio MS analysis of both delta(13)C and delta(15)N. The technique was shown to be highly reproducible, independent of the tablet matrix and considerably faster than existing liquid-liquid extraction methods. Crucially, no significant isotopic fractionation was observed as a result of the extraction process.

Isotope ratio mass spectrometry as a tool for forensic investigation (examples from recent studies).

The versatility of isotope ratio mass spectrometry is demonstrated by reference to diverse case studies. Variations in the natural isotopic composition of non-biological, organic materials are compared as a means by which samples may be associated or discriminated. These techniques may be used to augment or compliment conventional forensic methodologies. delta13C analysis was used to demonstrate that different masking tape had been recovered in two, apparently similar cases, involving the smuggling of money. Visually similar ecstasy tablets were compared by consideration of the delta13C and delta15N composition of MDMA extracted from the tablets. Although only a limited number of tablets were analysed, the isotopic similarity between two different seizures was sufficient to induce a guilty plea from a person suspected of possessing both. A combination of delta2H, delta13C, delta15N and delta18O together with GC-MS analyses were applied to small samples of seized heroin. Although GC-MS analysis indicated differences between the chemical composition of two of the heroin samples, isotopic analysis suggested similarities, which were confirmed by further delta2H, delta13C and delta18O isotopic analysis of the clingfilm in which the samples were wrapped.

Forensic isotope ratio mass spectrometry of packaging tapes.

Pressure sensitive adhesive tape (brown parcel tape) is employed in a great many criminal activities such as the restraint of individuals during robbery and offences against the person, the enclosure of explosive devices and the packaging and concealment of controlled drugs. Packaging materials are ubiquitous in modern society and are produced in such vast quantities that it is increasingly difficult to distinguish between different products or to link materials to a common source. This study demonstrates the potential of stable isotope ratio mass spectrometry to characterise parcel tapes based on a number of properties. The carbon isotopic signature, derived from the substrate polymer, associated additives and adhesive is highly characteristic of a particular tape and allows samples from different sources to be readily distinguished. Further discrimination may be achieved by the incorporation of deuterium and oxygen isotopic data and by analysis of the isolated backing polymer. Recovery of intact tape from simulated forensic samples proved straightforward and the isotopic signature of the tape did not appear to be affected by adverse storage conditions.