Forensic analysis elements analysed

A comprehensive approach to a states response to a chemical terrorism includes having a plan not only for the crisis and consequence management phases of the incident, but also for all elements required for complete resolution of the event. This may include the necessity to definitively establish whether chemical agents were used, to provide supporting evidence to confirm other analyses, or to provide the forensic proof required to support a criminal prosecution. The collection and analysis of biomedical samples - blood, urine or other tissue from affected humans or animals - is one of the means for providing such information. Although current capabilities such as urinary thiodyglycol excretion or plasma cholinesterase activity can be performed, there is scope for far more sensitive and specific assessments that overcome the limitations of these approaches. 

Neutron activation analysis is an attractive method in many trace element problems, or where the total amount of sample is limited. Many geochemical studies of trace constituents and semi-conductor developments have used the technique, whilst in recent years pollution investigations have provided a new focus. In forensic science small flakes of paint, single hairs and a variety of other small samples have been analysed and identified by activation analysis. In recent years activation analysis has lost further ground to ICP-MS which provides more comprehensive information and is more readily operated. Sensitivity is also comparable in many cases. 

SEMs are now often equipped with an energy-dispersive X-ray (EDX) analysis system for the elemental analysis of certain specimens. For example, the standard forensic laboratory test for identifying gunshot residue is based on the use of an electron microscope equipped with an EDX analyser. 

While the dual inlet technique is generally the most precise method for stable isotope ratio measurements, the continuous-flow technique offers online sample preparation, smaller sample size requirements, faster and simpler analyses, increased cost-effectiveness, and the possibility of interfacing with other preparation techniques, including elemental analysis, gas chromatography (GC), and liquid chromatography (LC). For these reasons, CF-IRMS is the subject of the majority of research currently being conducted in the field of forensic science [1],... 

Meier-Augenstein and Fraser [81] present a case where stable isotope data from human tissue were utilized as forensic intelligence to assist in the identification of a murder victim and subsequently the apprehension of the killers. Rauch et al. [82] demonstrate the application of IRMS to the measurement of stable isotope values (H, C, N) in combination with the measurement of heavy elements (Pb, Sr) of hair and teeth samples from an unknown body in Germany. These analyses assigned the man to Romania, in a situation where traditional forensic techniques (e.g., dental, fingerprint or DNA analysis) could not assist. 

In the early history of chemistry, all chemists found themselves performing analyses of one kind or another. In more recent times, analytical procedures have become much more sophisticated, and analytical chemistry has in consequence become a specialised branch of the subject. The skills of the analyst are now utilised not only by other chemists, but also by those carrying out investigations in fields such as forensic science, environmental science and the quality control of all manner of products. Some analytical techniques (for example the quantitative elemental analysis of organic compounds and the investigation of molecular structure by physical methods) have been considered in earlier chapters. 

In favourable circumstances, over 30 elements can be analysed without recourse to chemical separation, but the time scale of the analysis might be several weeks. In many practical cases, for example the analysis of forensic specimens, time may be the determining factor in the choice of an analytical technique. 

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