Arson debris

Recovery and Identification of Residues of Flammable Liquids from Suspected Arson Debris... 

This paper presents a current summary of methods and instrumentation utilized in the recovery and analysis of traces of flammable accelerants in arson debris. 

Numerous methods are available in the recovery of trace quantities of flammable accelerants from arson debris. Of these, four basic methods are generally preferred and have been found to be adequate in most cases encountered by forensic chemists. Each of these methods possesses good and bad features and consideration must be given to those features in contemplating the recovery of accelerants from any particular piece of evidence. 

Frequently, the residual portion of the accelerant present in arson debris nay be so small in quantity that the comparison of the resulting chromatogram with a known standard is inconclusive. 

Of the solvents pentane, hexane, and carbon disulfide, which would be the best choice for analyzing arson debris with GCFID ... 

New methodologies and the use of selected-ion monitoring (SIM) have made GCMS the detector of choice. GCMS has been used in the past for the detection and identification of single components, such as solvents, or ignitable liquid products with few components. Forensic scientists recognized the value of the mass spectrometer for identification of compounds in arson debris as early as 1976 (197). It had not been used routinely in the crime laboratory, however, until recently. 

Keto, R. O. (1995). GC/MS data interpretation for petroleum distillate identification in contaminated arson debris, Journal of Forensic... 

Solid materials, including soils, polymers, foods, vegetation, and arson debris, just to name a few, are rarely purged in the kind of vessel used for a liquid sample, since the frit serves no purpose in these cases and would only be a point of contamination. Instead, the samples are generally placed into a heated flow-... 

Mr. Mldklff continues, "When a sample from a suspected arson is examined by gas chromatography, additional peaks from materials present at the scene, as for example, plastics, in the sample may be observed. These additional peaks make difficult pattern recognition, normally relied upon for detectlon/ldentlfIcation of flammable liquids in the debris. Similar problems may be encountered in the analysis of samples from a bomb scene where chemicals in soil or debris from the bomb crater complicate the detection and identification of explosive components. 

Following ultraviolet-visible spectrophotometry and infrared (IR) spectroscopy, gas chromatography (GC) was one of the first instrumental techniques to help in solving forensic science problems. The early very successful applications included the determination of blood alcohol by direct injection of blood or serum, and the detection and identification of petroleum products in debris from arson cases in 1958/59. The breakthrough of GC in these areas and in drug analysis was an event of the 1960s and the 1970s. 

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... 

Arson investigations The use of NMR spectroscopy has been reported to complement the results of other methods for analyzing debris from suspected arson cases. The type of accelerant used to start the fire can be identified by the relative sizes and shapes of the peaks in different regions of the NMR spectrum - the strictly aliphatic portion from 0 to 2 ppm, the aliphatic moieties attached to aromatic components from 2 to 3 ppm, and the aromatic region from 6.5 to 7.5 ppm. Thus, paint thinner, lighter fluid, kerosene, diesel fuel, and various brands of gasoline all give their own unique patterns. These patterns... 

Steffen, A. Pawliszyn, J. Determination of liquid accelerants in arson suspected fire debris using headspace solid-phase microextraction. Anal. Commun. 1996, 33, 129-131. 

Debris recovered from the fire scene is often wet and burned, and may consist of material such as wood, carpet, carpet padding, tile, and other synthetic materials, all of which can contribute interfering volatile pyrolysis products that can make the identification of the accelerants difficult. The loss of accelerants through adsorption into the debris, evaporation from the heat of the blaze, and the presence of water all contribute to make the identification of accelerants a challenging task. GC can be a powerful tool in the analysis to separate and identify the accelerant in the presence of these interferences. Fultz and DeHaan have written an excellent chapter on GC in arson and explosive analysis (156). 

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