Fire debris analysis

In forensic science, chromatography is used in the analysis of drugs of abuse, toxicology, fire debris analysis, environmental analysis, and explosives analysis, to name but a few. To understand each of the chromatographic techniques, especially HPLC as the topic of this primer, it is necessary first to explain what chromatography is and the basic principles of chromatography. 

Finally, there are analyses within forensic science, where static headspace gas chromatography can be used as a part of a more complex analysis as fire debris analysis (Ren Bertsch, 1999 Sandercock, 2008), where the static headspace analysis provides complementary information to that provided by dynamic headspace techniques, for the determination of amphetamines and methamphetamines by the addition of potassium carbonate to transform the amine of the stimulant in its unprotonated, volatile form (Seto, 1994), and more recently, the study to substances produced during corpse decomposition (Statheropoulos, et al., 2005 Swann, et al., 2010), where different types of separation techniques are used to characterize the compounds produced in the decomposition and determine how they are produced. 

Lennard C (2001) Fire cause and fire debris analysis. In Tontarski RE, Jr. (ed.) Proceedings of the 13th Interpol International Forensic Science Symposium, 16-19 October. US Department of Justice. 

The introduction of commercially produced, activated charcoal strips into fire-debris analysis has provided an easy, efficient, and cost-effective method for accelerant extraction. However, several parameters require consideration to obtain a truly representative sample of accelerant. Newman, Dietz, and Lothridge have investigated the effects of time, temperature, charcoal strip size, and sample concentration on the adsorption of common accelerants. 

Carbon disulfide (CS2) has long been the solvent of choice for the elution of adsorption packages (e.g., activated charcoal strips) used in fire-debris analysis. The selection of CS2 stems from its efficiency at displacing materials adsorbed onto charcoal and its minimal response with the flame ionization detector. Unfortunately, CS2 is highly flammable and extremely toxic, and possesses a strong, unpleasant odor. In laboratories that utilize mass selective detectors instead of the F.I.D., diethyl ether, a much friendlier solvent, can be used instead of CS2. 

Stauffer, E., and J. J. Lentini. "ASTM standards for fire debris analysis a review." Forensic Science International 132 (2003), 63-67. 

Table 10.2 ASTM Standards Relevant to Fire Debris Analysis...

Figure 10.5 An illustration of why control samples are critical in fire debris analysis. 

Gilbert, M. W. "The Use of Individual Extracted Ion Profiles versus Summed Extracted Ion Profiles in Fire Debris Analysis." Journal of Forensic Sciences 43 (1998), 871-876. 

In fire debris analysis, weathering is manifest by an increase in chromatographic peaks with relatively higher molecular weights, whereas in ink evidence, weathering is manifest by a shift to lower molecular weights. Why ... 

On-line SFE-GC-MS was used for the analysis of organic extractables from human hair [312]. Van Lieshout et al. [313] described GC-MS analysis of an SFE extract of an (ABS) impact-modified PC/PBT blend identifying Ionol CP, Dressinate, cyclic PBT trimer, Irganox 1076 and Irganox PS 800. TD-GC-MS was used in the development of flame retardants, and for the analysis of fire debris [314]. The application of laser desorption fast GC-MS analysis was employed in the analysis of DOP on a stainless-steel surface [221]. 

K. G. Furton, J. Bruna, J. R. Almirall, A simple, inexpensive, rapid, sensitive and solventless technique for the analysis of accelerants in fire debris based on SPME, J. High Resolut. Chromatogr., 18, 625 629 (1995). 

The main method applied in analysis of fire debris is GC. The analysis of fire debris has three stages. The first stage is isolation of accelerants from the matrix and their concentration, followed by separation of particular components and their chromatographic analysis and, last, identification of potential accelerants. The efficiency of the first stage strongly determines the possibility of identification of the isolated and adsorbed organic compounds. An improperly performed first stage could make it impossible to identify the questioned substances. 

The investigator samples debris most likely to contain an ILR in sufficient quantity to enable detection and identification. A range of field detection methods are available to assist the investigator in locating fire debris for laboratory analysis. 

Chemical analysis of fire debris submitted to the laboratory is usually intended to establish the presence of ILRs. The analysis procedure consists of three separate steps (1) sample preparation - extraction (2) analysis of the extracted volatiles to yield a chromatographic profile and (3) data interpretation -identification of the ILR profile by comparison with known products. 

Bertsch W and Ren Q (2000) The Chemical Analysis of Fire Debris for Potential Accelerants. Handbook of Analytical Separations, vol. 2, ch. 18. Amsterdam Elsevier. 

GC was introduced very early as the technique of choice for the detection and identification of accelerants in debris from arson cases because of its high selectivity and sensitivity. But to use the full potential of the technique the methods of recovery of traces of common accelerants from fire debris had to be developed and adjusted. The used methods include solvent extraction, direct headspace analysis, and enrichment by adsorbent-based techniques. In the past, the most common concentration steps prior to the analysis have been (heated) headspace direct injection using a gastight syringe for analyte collection and GC injection or headspace adsorption techniques, mostly using charcoal followed by carbon disulfide (CSi) elution. Some of these procedures have been quite effective and are standardized by... 

Separation/concentration of flammable and combustible residues from fire debris samples by dynamic headspace ASTM E1413 analysis... 

Other forensic samples require different methods of preparation. Biological fluids often may be analyzed directly, or after the addition of a small amount of D2O for signal frequency locking. Plant material, tissue samples, and biological fluids may be put through extraction procedures to obtain samples suitable for NMR analysis. Explosives and accelerant samples may be prepared by normal chemical procedures. Postexplosion residues and fire debris may be extracted, and samples from these extracts prepared in the normal way. 

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