Sean P. Doyle

Determination of chlorine containing species in explosive residues using chip-based isotachophoresis

A new method has been developed to allow the determination of the chlorate, chloride and perchlorate anions in inorganic explosive residues to be made using isotachophoresis (ITP). To enable a good separation of these species to be achieved the method involves the use of two complexing agents. Indium(III) is used to allow the determination of chloride whilst using nitrate as the leading ion and alpha-cyclodextrin is used to allow the separation of chlorate and perchlorate. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. The method was applied to analysing both model samples and actual inorganic explosive containing residue samples. Successful determinations of these samples were achieved with no interference from other anions typically found in inorganic explosive residues. Limits of detection (LOD) for the species of interest were calculated to be 0.80 mg l(-1) for chloride, 1.75 mg l(-1) for chlorate and 1.40 mg l(-1) for perchlorate.

Quality assurance testing of an explosives trace analysis laboratory- : Further improvements

Abstract:  The Forensic Explosives Laboratory (FEL) operates within the Defence Science and Technology Laboratory (DSTL) which is part of the UK Government Ministry of Defence (MOD). The FEL provides support and advice to the Home Office and UK police forces on matters relating to the criminal misuse of explosives. During 1989 the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could, if other precautions failed, result in the contamination of samples and controls. Designated areas within the laboratory are swabbed using cotton wool swabs moistened with ethanol water mixture, in equal amounts. The swabs are then extracted, cleaned up and analyzed using Gas Chromatographs with Thermal Energy Analyzer detectors. This paper follows on from a previous published paper describing the regime and summarizing subsequent results from approximately 6 years of tests. Lessons learned and improvements made over the period are also discussed. Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has demonstrated that in this environment the risk of forensic sample contamination, assuming all the relevant anti‐contamination procedures have been followed, is so small that it is considered to be negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated

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.

Thiocyanate and nitrite analysis using miniaturised isotachophoresis on a planar polymer chip

A new method has been developed to improve the determination of thiocyanate using isotachophoresis. This method uses complexation with copper(II) as a mechanism for improving the separation of thiocyanate from chlorate and perchlorate. By using a pH of 3.25 the method can also be used to analyse nitrite. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. Linearity was observed from 1.25 to 75 mg dm(-3) with a correlation coefficient of 0.998 for both thiocyanate and nitrite. Limits of detection for these two species were calculated to be 0.8 mg dm(-3) and 0.9 mg dm(-3) respectively. The method was successfully applied to the analysis of these anions in a range of samples including explosive residues.

Network developing forensic applications of stable Isotope Ratio Mass Spectrometry conference 2005

Prof. Max Coleman of Reading University and Sean Doyle of the Forensic Explosives Laboratory (FEL), Dstl, formed the Forensic Isotope Ratio Mass Spectrometry (FIRMS) Network in 2002. As part of the continuing network development the second FIRMS conference, FIRMS 2005, was held at the Thistle Hotel, Brands Hatch, Kent on the 9th and 10th March 2005. The conference aimed to bring together IRMS researchers, end users and instrument manufacturers. The objectives of the conference were to exchange information between the researchers and end users; expand the network; review the requirement; assess the strategy for development; and chart progress since the first FIRMS conference. The conference was a mix of presentations and discussion sessions. A summary of each presentation and the discussions are given in this paper. Sean Doyle welcomed everyone to the second FIRMS conference and thanked participants for their continued support of the network. Dr. Robin Hiley, Chief Technologist, Energetics Department, Dstl was then introduced as the chairperson for the first day.

Determination of the potassium content of explosive residues using miniaturised isotachophoresis

A new method has been developed to allow the determination of potassium in post‐explosion residues to be made using miniaturised isotachophoresis. The method is based on the use of a caesium leading ion with 4.5 mM 18‐crown‐6 ether added to retard the potassium to allow reliable determinations to be made. With the conditions selected no interference was noted from other small inorganic cations, such as ammonium, barium, calcium, magnesium, sodium or strontium. The method was successfully applied to the analysis of seven samples containing explosive residues obtained from the unconfined burning of several flash powders. The procedure was found to offer good linearity for potassium determinations over the concentration range of 1.25–150 μg/mL with a coefficient of determination of 0.999 achieved.

The AFSP Standard - a lesson for law enforcement agencies.

Compliance with the AFSP (Association of Forensic Science Providers) Standard [1] which concerns the formulation of an evaluative opinion requires consideration of the defence case. This can be problematic for forensic scientists working with or for law enforcement agencies. Among the aims of law enforcement agencies is to secure a conviction while in many jurisdictions the forensic scientist owes an overriding duty to the Court. This casework report demonstrates that early consideration of the defence case by a forensic scientist complying with the AFSP Standard may help rather than hinder the prosecution. The dichotomy as to a conflict of interest for the scientist between supporting the police/prosecutors and being scientifically objective is shown to be a false dichotomy. Compliance with the Standard ensures that science is a better servant of justice.