Standard Test Method for Extraction and Derivatization of Fatty Acid-Based Products from Fire Debris and Liquid Samples with Analysis by Gas Chromatography-Mass Spectrometry

Importancia y uso:

5.1 This test method is useful when oils and fats could be present as an ignition source or a fuel source in a fire.

5.1.1 The identification of oil and fat residues in debris and liquid samples from a fire scene can provide data relevant to judgments regarding investigative leads and the origin and cause of a fire.

5.1.2 The identification of fatty acid(s) alone is insufficient for an opinion that the fire was caused by self-heating or for providing a probability that the fire was caused by self-heating.

5.2 This test method identifies fatty acid derivatives. Oils and fats are comprised primarily of triglycerides (which are fatty acids attached to a glycerol backbone), and some free fatty acids. Free fatty acids and triglycerides are not easily analyzed by traditional ignitable liquid extraction techniques. Solvent extraction and derivatization to FAMEs enables identification by GC-MS.

5.2.1 The identification of an oil or fat is based on the presence of two or more fatty acids. The presence of a single fatty acid in fire debris samples is insufficient to confirm the presence of oils or fats.

5.2.2 Oils and fats containing fatty acids with no double bonds will generally have no tendency to self-heat. With increasing unsaturation (one, two, and three double bonds), the tendency toward self-heating increases, such that polyunsaturated fatty acids (PUFAs), such as C18:3, have a high tendency to self-heat.4

5.3 This test method is performed after all required traditional testing for ignitable liquid residues is completed. Refer to Guide E3245.

5.4 This test method extracts liquids and residues from porous and nonporous materials of various sizes.

5.5 This test method is not intended to be used on the entire fire debris sample. Substrates can contain low levels of fatty acids. Extracting the entire sample complicates the interpretation due to coincident extraction of interfering compounds present in the fire debris. It is recommended that visual inspection be used to locate portions or areas exhibiting potential oily residue for sub-sampling which would preserve remaining portions for further analyses and minimize solvent waste.

5.6 This test method is not suitable for products containing components that have already been converted to FAMEs.

5.6.1 Biodiesel, an ignitable liquid, is a trans-esterified product containing FAMEs. The FAME compounds in biodiesel can be detected in fire debris using traditional fire debris extraction techniques followed directly by GC-MS analysis (refer to Test Method E2997). Derivatization is not necessary to identify the FAMEs in biodiesel.

5.7 This is a destructive technique, and whenever possible, it is recommended that the entire fire debris sample not be used for the procedure. The solvent extracted portions of the sample are not suitable for resampling.

5.8 For more information on oils, FAMEs, and fire debris analysis, see the references listed.4^, 5^, 6^, 7

Subcomité:

E30.13

Referida por:

E2997-25, E3245-20E01

Volúmen:

14.02

Número ICS:

67.200.10 (Animal and vegetable fats and oils)

Palabras clave:

animal fats; fatty acid-based products; fatty acid methyl esters; FAME; fire debris samples; forensic sciences; gas chromatography; ignitable liquid residues; mass spectrometry; vegetable oils;