Identification Of Ignitable Liquid Residues Research Articles

Hydrocarbon retention on activated carbon: Preservation of fire debris evidence

Fire debris is collected and analyzed to determine whether volatile hydrocarbons of ignitable liquids (IL) are present. Typically, the hydrocarbons from fire debris are separated from the debris by adsorption onto activated carbon. Laboratory generated fire debris were sampled by adsorption onto activated charcoal strips (ACS) where half of the ACS was analyzed by gas chromatography – mass spectrometry (GC–MS) and the other half was preserved for 14 years [1,2]. Reference ignitable liquids are important in the detection and identification of ignitable liquid residues (ILR) from fire debris [3]. Reference IL contain 400 µl of IL adsorbed onto 0.5 g of granular activated carbon (GAC) and were preserved for 21 years. Comparisons of the chromatographic profiles at Day 0 and Year X (X = 14 or 21) were performed by Spearman rank correlation of selected peak’s intensities and visual inspection to determine how well these samples were preserved. The fire debris samples on ACS had an average Spearman rank correlation coefficient of 0.90 with a standard deviation of 0.11. Thirty-six percent of them demonstrated no change in the chromatographic profile and 64 % of them demonstrated minimal desorption in the chromatographic profile. The GAC samples had an average Spearman rank correlation coefficient of 0.95 with a standard deviation of 0.12. Eighty-two percent of them demonstrated no change in the chromatographic profile. This study reveals that hydrocarbons of ignitable liquids on activated carbon following established preservation procedures remain useful for forensic purposes after long-term storage.

Interference from combustion residues of polystyrene-butadiene involving ‘alkylbenzenes’ in molecules on gasoline identification

ABSTRACT The interference of background at fire scene on identification of ignitable liquid residues (ILRs) is an ongoing concern in fire investigation. The current study aims to determine potential interference on gasoline identification from the combustion/pyrolysis products of polystyrene-butadiene rubber (SBr) involving ‘alkylbenzenes’ in molecules. Gas chromatography–mass spectrometry (GC/MS) analysis results of extracts from combustion residues of SBrs, SBrs loaded with gasoline and gasoline were compared. Commonly encountered compounds interfering gasoline identification, including the alkylbenzenes, naphthalenes, as well as indanes, were obtained in all the combustion residues of the SBrs by analysing the extracted ion chromatogram (EICs) of the combustion/pyrolysis products. Furthermore, for gasoline loaded onto SBr substrate, the SBr causes significant distortion to gasoline combustion residues by changing the comparative contents of the target compounds for gasoline identification. Overreliance on the target compounds for gasoline identification could lead to misidentifications in the presence of SBrs combustion residues, while the typical ratios of the target compounds in gasoline combustion residues would also be affected when encountered with SBrs, especially for the cases of smaller loading of gasoline. A detailed examination of the C3-alkylbenzenes and C4-alkylbenzenes profile should be part of any fire debris analysis.

Influence of thermal environment in fire on the identification of gasoline combustion residues

Recent advances in fire investigation have engendered significant interest in fire debris analysis. Many factors in fire scenes, however, may interfere with the identification of ignitable liquid residues (ILRs). Generally, all ILRs suffer unavoidably from thermal destruction in fires. In contrast to weathering, the thermal effects on ILRs involve evaporation, thermal degradation and other chemical reactions. In order to study the influence of the thermal environment in fire scenes on the stability of target compounds for ILRs identification, gasoline combustion residues were reheated at different temperatures and analyzed by gas chromatography-mass spectrometry (GC–MS) systematically. The results showed that polycyclic aromatic hydrocarbons (PAHs) and indanes were more susceptible to thermal destruction, and could not be detected effectively after heating. On the other hand, alkylbenzenes and condensed ring aromatics were comparatively more stable. When the temperature rose to 600 °C, almost all the target compounds were lost after reheating again for 2 min. The research provides an important reference for gasoline combustion residues identification, and care should be taken on the interpretation of results due to the inevitable thermal damage to ILRs in fires.

Effect of Different Matrices on the Identification of Ignitable Liquid Residue in Post Burn Arson Debris: A Multi-Derivative UV-Visible Spectrophotometric Approach

Analysis of arson debris is the foremost challenging task to the forensic investigators. Identification of the ignitable liquid residues in the fire debris is one of the prime objectives of forensic quest. This study evaluates the potential of derivative ultraviolet-visible spectrophotometric methods for the analysis and identification of ignitable liquid residues. In this work, arson was simulated using kerosene as an ignitable liquid on various matrices. Derivative UV spectra of kerosene were recorded in their neat state and compared with those obtained from simulated fire debris samples for the identification and detection of ignitable liquid residues. It was observed that different burnt substrates did not cause any interference. The obtained results indicated that the ignitable liquid absorption capacity of the substrate can play an important role in the extraction and identification of ignitable liquid from fire debris. The used technique proved to be rapid, easy, reproducible and efficient.

Novel method based on ion mobility spectrometry sum spectrum for the characterization of ignitable liquids in fire debris

The destructive nature of fire together with a variety of interfering products from pyrolysis or background compounds among others, still offer a challenge on the proper identification of ignitable liquid residues (ILRs) in fire investigations. Nowadays, analysts use chromatography-mass spectrometry to try and classify ignitable liquids (IL) into one of the classes in the American Standards Testing Material method (ASTM E1618). In this study, an alternative approach is proposed to such analysis of fire debris. The proposed method would be based on ion mobility spectrometry sum spectrum (IMSSS) from headspace analysis, in combination with pattern recognition tools (Linear Discriminant Analysis, LDA). Four different substrates (pinewood, cork, paper, and cotton sheet) were burnt with and without different ILs (gasoline, diesel, ethanol, and paraffin). According to LDA, 100% of fire debris samples were correctly classified for presence/absence and type of IL. A characteristic fingerprint for each ILR was created for quick discrimination. These results demonstrate the potential of using IMSSS for a fast, objective and easy interpretation of fire debris data. In addition, ion mobility spectrometry (IMS) presents some advantages over traditional techniques such as its real-time monitoring capability and its capacity to work at atmospheric pressure, which allow the development of portable devices that would perform the analysis at the fire scene.

The potential interference of body products and substrates to the identification of ignitable liquid residues on worn clothing

The question of whether deposits on clothing as well as their chemical composition are being mistaken for ignitable fluids is a concern for forensic analysts. Body products and oil secretions can have similar chemical profiles to ignitable liquid residues (ILRs) as a result of comparable chemical compounds that may be found in both sources. This study investigated whether substrates of unworn and worn clothing, with endogenous body secretions and body products could interfere with ILR analysis. Sample extraction was completed by passive headspace concentration with activated charcoal strips (ACS) and desorption with carbon disulfide followed by analysis with gas chromatography-mass spectrometry (GC–MS). Results showed that some body products produce similar patterns to heavy petroleum distillates and most clothing contained components that are commonly found in ignitable liquids. It was concluded that the clothing, body products and compounds released by the body all contribute to the GC–MS profile of worn clothing. These components can mimic or mask the presence of ILRs, however educated and experienced analysts would likely be able to differentiate these substrate patterns from ILRs.

Developing a Method for the Collection and Analysis of Burnt Remains for the Detection and Identification of Ignitable Liquid Residues Using Body Bags, Dynamic Headspace Sampling, and TD-GC×GC-TOFMS

In cases of suspected arson, a body may be intentionally burnt to cause loss of life, dispose of remains, or conceal identification. A primary focus of a fire investigation, particularly involving human remains, is to establish the cause of the fire; this often includes the forensic analysis of fire debris for the detection of ignitable liquid residues (ILRs). Commercial containers for the collection of fire debris evidence include metal cans, glass jars, and polymer/nylon bags of limited size. This presents a complication in cases where the fire debris consists of an intact, or partially intact, human cadaver. This study proposed the use of a body bag as an alternative sampling container. A method was developed and tested for the collection and analysis of ILRs from burnt porcine remains contained within a body bag using dynamic headspace sampling (using an Easy-VOC™ hand-held manually operated grab-sampler and stainless steel sorbent tubes containing Tenax TA) followed by thermal desorption comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (TD-GC×GC-TOFMS). The results demonstrated that a body bag containing remains burnt with gasoline tested positive for the presence of gasoline, while blank body bag controls and a body bag containing remains burnt without gasoline tested negative. The proposed method permits the collection of headspace samples from burnt remains before the remains are removed from the crime scene, limiting the potential for contamination and the loss of volatiles during transit and storage.

Application of Headspace Gas Chromatography-Ion Mobility Spectrometry for the Determination of Ignitable Liquids from Fire Debris

A fast and correct identification of ignitable liquid residues in fire debris investigation is of high importance in forensic research. Advanced fast analytical methods combined with chemometric tools are usually applied for these purposes. In the present study, the Headspace Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS) combined with chemometrics is proposed as a promising technique for the identification of ignitable liquid residues in fire debris samples. Fire debris samples were created in the laboratory, according to the Destructive Distillation Method for Burning that is provided by the Bureau of Forensic Fire and Explosives. Four different substrates (pine wood, cork, paper, and cotton sheet) and four ignitable liquids of dissimilar composition (gasoline, diesel, ethanol, and paraffin) were used to create the fire debris. The Total Ion Current (TIC) Chromatogram combined with different chemometric tools (hierarchical cluster analysis and linear discriminant analysis) allowed for a full discrimination between samples that were burned with and without ignitable liquids. Additionally, a good identification (95% correct discrimination) for the specific ignitable liquid residues in the samples was achieved. Based on these results, the chromatographic data from HS-GC-IMS have been demonstrated to be very useful for the identification and discrimination of ignitable liquids residues. The main advantages of this approach vs. traditional methodology are that no sample manipulation or solvent is required; it is also faster, cheaper, and easy to use for routine analyses.

The surprising effect of temperature on the weathering of gasoline

During the identification of ignitable liquid residues in fire debris, it is well known that evaporative losses result in a general increase in the abundance of non-volatile residues relative to volatile residues. However, previous work has provided an incomplete understanding of weathering such that we cannot adequately relate weathered residues to un-weathered pristine samples. Here, we studied various factors that influence the relative abundance of weathered residues.Real gasoline samples were weathered to varying extents, at different temperatures, and under conditions of a vacuum or a nitrogen stream. Analysis of the liquid residues was performed using gas chromatography mass spectrometry (GC/MS), which showed that, as expected, the extent of weathering has the largest effect on the abundance of different residues. However, the results also showed that at a constant extent of weathering, the earliest eluting compounds—like toluene and the C2-alkyl benzenes—tend to remain at significantly higher levels (α<0.05) at higher temperatures than at lower temperatures.Experimental weathering and mathematical simulations were also performed on a simpler seven-component mixture. Weathering simulations closely follow the experimental data below 100°C, even up to 95% weathering. The model was extrapolated to significantly elevated temperatures, which showed that heavily weathered (95%) gasoline at high temperature (500°C) would be almost indistinguishable from a liquid that is weathered to a lesser extent (70%) at room temperature. These results provide an alternative or additional explanation for why gasoline recovered from arson scenes does not appear to be as weathered as one would expect.

Study of acidified ignitable liquid residues in fire debris by solid-phase microextraction with gas chromatography and mass spectrometry.

The detection and identification of ignitable liquid residues in fire debris can be meaningful in fire investigations. However, background pyrolysis products and weathering hinder the identification and classification steps. In addition to those processes, the acidification of the ignitable liquids before the combustion process could make those tasks even more difficult. Nevertheless, there are no systematic studies assessing the extraction, analysis, and composition of acidified ignitable liquid residues obtained from fire debris. In this work, a method for the study of acidified ignitable liquid residues in fire debris by solid-phase microextraction with gas chromatography and mass spectrometry is proposed. This methodology has been evaluated, first with simulated solutions (gasoline/sulfuric acid mixtures set on fire under controlled conditions), and then with analysis of samples from real fire debris obtained from 18 chemical ignition Molotov cocktails made with sulfuric acid and three different ignitable liquids (two types of gasoline and diesel fuel). In addition, the extensive modifications observed in chromatograms of acidified ignitable liquid residues regarding neat and weathered samples were studied. These alterations were produced by the combustion and acidification processes. As a consequence, tert-butylated compounds are proposed as diagnostic indicators for the identification of acidified gasoline in fire debris, even in strongly weathered samples.

Headspace sorptive extraction for the detection of combustion accelerants in fire debris

A novel method for separation and identification of ignitable liquid residues in fire debris by gas chromatography and mass spectrometry is presented. Preconcentration of the analytes was carried out using the simple headspace sorptive extraction (HSSE) technique. Polydimethylsiloxane stir bars were used as the enrichment phase, and parameters affecting both the adsorption and desorption stages were carefully optimized. Extraction was carried out at 50°C for 1h. Stir bars were desorbed thermally in the GC injection port, thus avoiding the use of organic solvents. The results for five ignitable liquids, including gasoline and diesel fuel, using HSSE were compared with those obtained with a solid-phase microextraction method, with HSSE appearing as a more sensitive alternative.

Association of Ignitable Liquid Residues to Neat Ignitable Liquids in the Presence of Matrix Interferences Using Chemometric Procedures*,†

In fire debris analysis, weathering of ignitable liquids and matrix interferences can make the identification of ignitable liquid residues (ILRs) difficult. An objective method was developed to associate ILRs with the corresponding neat liquid with discrimination from matrix interferences using principal components analysis (PCA) and Pearson product moment correlation (PPMC) coefficients. Six ignitable liquids (gasoline, diesel, ultra pure paraffin lamp oil, adhesive remover, torch fuel, paint thinner) were spiked onto carpet, which was burned, then extracted using passive headspace extraction, and analyzed by gas chromatography-mass spectrometry. Both light and heavy burn conditions were investigated. In the PCA scores plot, ignitable liquids were discriminated based on alkane and aromatic content. All ILRs were successfully associated with the corresponding neat liquid using both PCA and PPMC coefficients, regardless of the extent of burning. The method developed in this research may make the association of ILRs with corresponding neat liquids more objective.

The effects of microbial degradation on ignitable liquids

The identification of ignitable liquid residues in fire debris is a key finding for determining the cause and origin of a suspicious fire. However, the complex mixtures of organic compounds that comprise ignitable liquids are susceptible to microbiological attack following collection of the sample. Biodegradation can result in selective removal of many of the compounds required for identification of an ignitable liquid. Such degradation has been found to occur rapidly in substrates such as soil, rotting wood, or other organic matter. Furthermore, fire debris evidence must often be stored for extended periods at room temperature prior to analysis due to case backlogs and available evidence storage. Hence, extensive damage to ignitable liquid residues by microbes poses a significant threat to subsequent laboratory work. In this work, the effects of microbial degradation of ignitable liquids in soil have been evaluated as a function of time. Key findings include the loss of n-alkanes, particularly C(9)-C(16), which showed the most dramatic decrease in gasoline as well as the petroleum distillates, while branched alkanes remained unchanged. Monosubstituted benzenes also showed the most dramatic loss in gasoline. In the heavy petroleum distillates, n-alkanes with even carbon numbers were degraded more than n-alkanes with odd carbon numbers.