Fire debris

Figure 15.9 Use of heart-cutting for the identification of target compounds in 90% evaporated gasoline. Peak identification is as follows 1, 1,2,4,5-teti amethylbenzene 2, 1,2,3,5-teti amethylbenzene 3, 4-methylindane 4, 2-methylnaphthalene 5, 5-methylindane 6, 1-methylnaphthalene 7, dodecane 8, naphthalene 9,1,3-dimethylnaphthalene. Adapted from Chromatography, 39, A. Jayatilaka and C.F. Poole, Identification of petroleum distillates from fire debris using multidimensional gas chromatography , pp. 200-209, 1994, with permission from Vieweg Publishing.

A. Jayatilaka and C. E. Poole, Identification of peti oleum distillates from fire debris using multidimensional gas chromatography , Chromatographia 39 200-209 (1994). 

ASTM E 1385-90, Standard Practice for Separation and Concentration of Flammable or Combustible Liquid Residues from Fire Debris Samples by Steam Distillation, American Society for Testing and Materials, Philadelphia, PA (1991). 

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). 

Explosives and evidence at a fire scene (fire debris) for determination regarding the origin and cause of the fire. 

Standard Practice for Separation and Concentration of Ignitable Liquid Residues in Extracts from Samples of Fire Debris by Gas Chromatography, ASTM E138701, ASTM, West Conshohocken, PA, 2001. 

One of the more recent application areas for GCxGC is forensic science, and it is expected that this area will grow because of the diversity of matrices that fall under the forensics science banner. Studies on fire debris and accelerants have been undertaken... 

A need for techniques to individualize accelerants by commercial brands or sources after recovery from fire debris. 

The most common microtraces examined in criminalistic laboratories are so-called contact traces (i.e. small fragments of paint coating, glass, single fibres, soil, writing materials). Moreover, traces of flammable liquids originating from fire debris or traces pointing to the use of firearms are revealed and identified. 

The spilled flammable liquids sink into the base (e.g. soil, textile, wood). The burning process only takes place on the surface of the base. Deep down, liquids hardly evaporate and bum very slowly some are occluded in porous materials created from synthetic materials during the fire. That is why it is possible to find traces of flammable liquids in fire debris in spite of them being burnt out of almost everything [23, 22]. 

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. 

Fig. 11.7 Chromatograms of samples of fire debris, from the can found in the subject s possession and gasoline evaporated to 50 %. The characteristic patterns are marked with rectangles...

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. 

Lu, Y., Harrington, P.B., Forensic applications of gas chromatography-differential mobility spectrometry with two-way classification of ignitable liquids from fire debris. 

An explosion occurred in a nigrosine base phenylator which resulted in a fire. Debris was scattered over a wide area but nobody was seriously hurt. The roof and windows of the building were extensively damaged. Damage to the plant and building was estimated at about 1.1 million (1996). 

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. 

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. 

There are many factors that contribute to the presence of fire debris that has retained an ILR however, many of these are beyond the control of the fire investigator. The investigator can only sample from what is available at the scene but needs to consider the properties of the matrix in retaining liquid residues. Porous or absorbent materials such as paper, books, carpeting, and fabric can retain a substantial amovmt of ignitable liquid and should be collected. If liquid is found in the debris, it should be transferred to a small glass vial using a pipette or... 

Recovery of Ignitable Liquids from Fire Debris... 

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. 

In this procedure, volatiles from the fire debris are adsorbed onto a suitable substrate such as a carbon-impregnated polymer commonly referred to as the carbon strip method. The process is determined by diffusion of volatiles to the surface of the adsorbent hence, it is considered to be a passive or static... 

Solid-phase microextraction (SPME) is a static head-space method similar to the carbon strip method however, it does not require a solvent desorption stage. Volatiles are extracted from the headspace by absorption into an absorbent polymer such as poly-dimethylsiloxane (ASTM method E2154). The absorbent polymer is coated onto a quartz fiber that is housed within a needle similar to a syringe needle. The coated fiber is exposed beyond the tip of the needle in the headspace above the fire debris. As with the carbon strip method, the fiber debris sample can be heated to increase the concentration of volatiles in the headspace. Volatiles are absorbed within the polymer with exposure times for routine screening being within the range 5-15 min. The fiber is retracted within the needle and can then be directly inserted into the injector of a gas chromatograph where the volatiles are thermally desorbed from the polymer onto the column. SPME fibers can be reused but appropriate blanks need to be run to ensure that the fiber is clean. 

This method can be applied when the adsorptive nature of the matrix may be problematic in extracting a representative sample. The fire debris is placed in a flask and extracted with an organic solvent. The volatile hydrocarbons that are miscible with the solvent are extracted from the debris. Commonly used solvents are carbon disulfide, dichloromethane, pentane, and hexane. The extract is filtered, evaporated to a small volume, and then analyzed. Sensitivity is similar to steam distillation however, interfering substances such as pyrolysis products are also extracted. 

Figure 1 shows the chromatogram of a medium product range petroleum distillate recovered from fire debris. This is characteristic of a petroleum distillate in that the predominant peaks are associated with a homologous series of n-alkanes in a Gaussian distribution with abundant but less significant isoparaffinic, cycloparaffinic, and aromatic compounds also present. These less significant... 

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