Dissertations / Theses on the topic 'Ignitable liquid'

United Kingdom fire investigators use ad hoc adsorbents to investigate the suspected use of ignitable liquids and their residues (ILR) at fire scenes. It was unknown whether these materials adsorb all ignitable liquid target compounds specified by ASTM methods, or if they interfered with such analysis and therefore prevented the positive identification of ignitable liquids. This research has ascertained that adsorbents such as clay based cat litter, montmorillonite, limestone, Tampax®, Tenalady®, talc; sand and the use of a squeegee tool cannot adsorb the full range of ASTM target compounds in common ignitable liquid residues by themselves. However, some can adsorb a limited range of target compounds. For example, cat litter can adsorb C3 and C4 alkylbenzenes and other molecules for the identification of petrol, but cannot adsorb heavy alkanes such as those found in diesel fuel. In contrast, limestone can adsorb heavy alkanes but not all aromatic target compounds present in petrol. This study has found that when limestone was mixed with Fuller’s Earth (10:1 w/w) that a range of common ignitable liquids and their associated target compounds could be adsorbed and identified. Furthermore, the instrumentation and separation methods used with an automated thermal desorption-gas chromatography-mass spectrometer (ATD-GC-MS) and Tenax TA® were improved and it is hoped that these would form a basis for a new standard method. Limestone and Fuller’s Earth as well as the limestone/Fuller’s Earth mixture were characterised with Fourier-Transform Infra-Red spectroscopy and X-ray Diffraction. The results showed that mixing the components together did not alter the chemical composition of the adsorbent mixture and that the major phases in the mixture were identified as calcite, quartz and palygorskite. The performance of the adsorbents was assessed using a combination of a standard ASTM method for analysis using GC-MS and an improved oven separation time of six to nine hours. The ATD method was improved for real fire debris samples by setting the split flow valves to 40 mL/min to minimise instrument overloading. The adsorbents were subjected to evaluation in the laboratory using blind tests and also a field blind test at a real fire scene. The laboratory analysis and fire scene evaluation revealed that the limestone/Fuller’s Earth mixture adsorbed all ignitable liquid target compounds from different ignitable liquids and as a result were identified from extracted ion chromatograms. This is the first reported use of this novel mixture as a universal adsorbent for common ignitable liquids.

Current fire debris analysis procedure involves using the chromatographic patterns of total ion chromatograms, extracted ion chromatograms, and target compound analysis to identify an ignitable liquid according to the American Society for Testing and Materials (ASTM) E 1618 standard method. Classifying the ignitable liquid is accomplished by a visual comparison of chromatographic data obtained from any extracted ignitable liquid residue in the debris to the chromatograms of ignitable liquids in a database, i.e. by visual pattern recognition. Pattern recognition proves time consuming and introduces potential for human error. One particularly difficult aspect of fire debris analysis is recognizing an ignitable liquid residue when the intensity of its chromatographic pattern is extremely low or masked by pyrolysis products. In this research, a unique approach to fire debris analysis was applied by utilizing the samples total ion spectrum (TIS) to identify an ignitable liquid, if present. The TIS, created by summing the intensity of each ion across all elution times in a gas chromatography-mass spectrometry (GC-MS) dataset retains sufficient information content for the identification of complex mixtures . Computer assisted spectral comparison was then performed on the samples TIS by target factor analysis (TFA). This approach allowed rapid automated searching against a library of ignitable liquid summed ion spectra. Receiver operating characteristic (ROC) curves measured how well TFA identified ignitable liquids in the database that were of the same ASTM classification as the ignitable liquid in fire debris samples, as depicted in their corresponding area under the ROC curve. This study incorporated statistical analysis to aid in classification of an ignitable liquid, therefore alleviating interpretive error inherent in visual pattern recognition. This method could allow an analyst to declare an ignitable liquid present when utilization of visual pattern recognition alone is not sufficient.
M.S.
Department of Chemistry
Sciences
Forensic Science MS

Thesis (M.S.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
Heated passive headspace concentration is presently the most commonly utilized technique for the extraction of ignitable liquid residues from fire debris evidence. This process, introduced by William Dietz in 1991, typically involves suspending an activated charcoal strip within an airtight container such as a metal can and incubating the sample for a period of time. ASTM Standard Practice E1412-07 advises heating the sample for 2 to 24 hours at a temperature of 50 to 80° Celsius. Subsequently, the compounds are easily eluted from the adsorbent with a suitable solvent, often carbon disulfide, and analyzed using gas chromatography/mass spectrometry (GC/MS) for the potential identification of any ignitable liquid residues. It is a simple, sensitive, and nondestructive method, and can often be performed within the original sample packaging. The activated charcoal strip, which does not interact with water or nitrogen, is advantageous in its affinity for hydrocarbons and resistance to oxidation. The technique is highly efficient for recovering petroleum-based ignitable liquids, however, it has had limited success with adsorbing and concentrating oxygenated species. In an effort to improve the recovery of ignitable liquids containing oxygenated compounds, previous studies have suggested zeolites are a suitable adsorbent for the recovery of acetone through heated passive headspace concentration. Zeolites are inorganic, microcrystalline materials that have a well-defined internal structure and uniform pore size. Most frequently aluminosilicate with internally dispersed cations, zeolite particles attract small organic molecules, including alcohols and ketones. Their high thermal and chemical stability make them ideal adsorbents for heated passive headspace applications. An additional advantage to utilizing zeolites involves their well-defined pore size, which is ideal for the selective adsorption of small organic molecules. Zeolite 13X is effective for recovering analytes with molecular diameters smaller than 10 Å, such as acetone (6.3 Å). A compound with a molecular diameter greater than the zeolite pore size may not gain access to the internal channels, and thus may not be internally adsorbed. The primary aim of this study was to further optimize the conditions for implementing zeolites as a viable extraction technique within fire debris casework, as a complement to the activated charcoal strip method. Extraction time and temperature, desorption solvent, and gas chromatography parameters were all examined with the goal of providing the most efficient recovery of five oxygenated volatile compounds: ethanol, 1-propanol, 1-butanol, isopropanol, and acetone. Recovery by the use of zeolites desorbed in methanol was up to triple in amount when compared to recovery by activated charcoal strips with carbon disulfide. This is in accordance with previous studies that reported a 320% improvement in acetone recovery by utilizing zeolites. In an effort to evaluate the ability of zeolite 13X to selectively adsorb oxygenated volatile compounds, comparative recoveries of mixtures of petroleum and alcohol-based ignitable liquids were studied utilizing activated charcoal strips and zeolites, individually and in tandem. In the presence of both adsorption media within the same can, the activated charcoal strips alone recovered three major components of gasoline (toluene, 1,2,4-trimethylbenzene, and naphthalene), while the zeolites recovered the majority of oxygenated compounds. This phenomenon is attributed to the size exclusion properties, polarity, and available surface area of the zeolites. This research supports the use of both zeolites and activated charcoal strips, in what is termed a dual-mode adsorbent preparation, for the simultaneous recovery of oxygenated and petroleum-based ignitable liquids in a single fire debris extraction procedure.

Fire incidents are a major contributor to the number of deaths and property losses within the United States each year. Fire investigations determine the cause of the fire resulting in an assignment of responsibility. Current methods of fire debris analysis are reviewed including the preservation, extraction, detection and characterization of ignitable liquids from fire debris. Leak rates were calculated for the three most common types of fire debris evidence containers. The consequences of leaking containers on the recovery and characterization of ignitable liquids were demonstrated. The interactions of hydrocarbons with activated carbon during the extraction of ignitable liquids from the fire debris were studied. An estimation of available adsorption sites on the activated carbon surface area was calculated based on the number of moles of each hydrocarbon onto the activated carbon. Upon saturation of the surface area, hydrocarbons with weaker interactions with the activated carbon were displaced by more strongly interacting hydrocarbons thus resulting in distortion of the chromatographic profiles used in the interpretation of the GC/MS data. The incorporation of an additional sub-sampling step in the separation of ignitable liquids by passive headspace sampling reduces the concentration of ignitable liquid accessible for adsorption on the activated carbon thus avoiding saturation of the activated carbon. A statistical method of covariance mapping with a coincident measurement to compare GC/MS data sets of two ignitable liquids was able to distinguish ignitable liquids of different classes, sub-classes and states of evaporation. In addition, the method was able to distinguish 10 gasoline samples as having originated from different sources with a known statistical certainty. In a blind test, an unknown gasoline sample was correctly identified from the set of 10 gasoline samples without making a Type II error.
M.S.
Department of Chemistry
Sciences
Forensic Science MS

Thesis (M.S.F.S.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
The ability to extract ignitable liquids from wooden fire debris samples is an important aspect of arson investigation. A common method by which the ignitable liquids are extracted is heated passive headspace extraction, a process by which a sample is heated in a sealed container and any ignitable liquid residues present desorb from the sample and adsorb to an adsorbent present in the container. An activated charcoal strip is most often used as the adsorbent, and the recommended extraction procedure is to allow the sample to extract in an oven set at a temperature between 50 °C and 80 °C for an amount of time between 8 and 24 hours. The ignitable liquid residues can then be eluted from the adsorbent and analyzed by gas chromatography-mass spectrometry (GC-MS) to identify the type of ignitable liquid present within the sample as well as specific compounds within the ignitable liquid. The extraction procedure typically does not yield 100% of the original amount of ignitable liquid deposited on the sample. Some of the ignitable liquid residue loss can be attributed to any irreversible adsorption that occurs between the substrate and the ignitable liquid. This irreversible adsorption is not known to be a constant across different wood genera; however, the extent of irreversible adsorption may vary between differing genera of wood. The focuses of this thesis are to examine any trends in irreversible adsorption that occur in wooden substrates, to see which genera of wood presents the greatest retention of ignitable liquids, and to see if any correlation exists between the retention capabilities of a wood genus and its density. The densities were determined for a total of thirteen common wood genera, which were spiked with one of three ignitable liquids and then subjected to heated passive headspace extraction. A semi-quantitative approach was taken by comparing the abundance of specific compounds within an ignitable liquid extracted from a wood substrate to the abundance present in a diluted sample of the same ignitable liquid, allowing a comparison between different genera to be made. Ultimately, it was determined that different genera of wood do display different retention capabilities for the common ignitable liquids examined in this thesis, but there was no genus of wood which consistently demonstrated a greater retention for the ignitable liquids compared to the other genera, nor was there a genus of wood which consistently allowed for greater recovery of the ignitable liquids compared to the other genera.
2031-01-01

Current methods in ignitable liquid identification and classification from fire debris rely on pattern recognition of ignitable liquids in total ion chromatograms, extracted ion profiles, and target compound comparisons, as described in American Standards for Testing and Materials E1618-10. The total ion spectra method takes advantage of the reproducibility among sample spectra from the same American Society for Testing and Materials class. It is a method that is independent of the chromatographic conditions that affect retention times of target compounds, thus aiding in the use of computer-based library searching techniques. The total ion spectrum was obtained by summing the ion intensities across all retention times. The total ion spectrum from multiple fire debris samples were combined for target factor analysis. Principal components analysis allowed the dimensions of the data matrix to be reduced prior to target factor analysis, and the number of principal components retained was based on the determination of rank by median absolute deviation. The latent variables were rotated to find new vectors (resultant vectors) that were the best possible match to spectra in a reference library of over 450 ignitable liquid spectra (test factors). The Pearson correlation between target factors and resultant vectors were used to rank the ignitable liquids in the library. Ignitable liquids with the highest correlation represented possible contributions to the sample. Posterior probabilities for the ASTM ignitable liquid classes were calculated based on the probability distribution function of the correlation values. The ASTM ignitable liquid class present in the sample set was identified based on the class with the highest posterior probability value.; Tests included computer simulations of artificially generated total ion spectra from a combination of ignitable liquid and substrate spectra, as well as large scale burns in 20'x8'x8' containers complete with furnishings and flooring. Computer simulations were performed for each ASTM ignitable liquid class across a range of parameters. Of the total number of total ion spectra in a data set, the percentage of samples containing an ignitable liquid was varied, as well as the percent of ignitable liquid contribution in a given total ion spectrum. Target factor analysis was them performed on the computer-generated sample set. The correlation values from target factor analysis were used to calculate posterior probabilities for each ASTM ignitable liquid class. Large scale burns were designed to test the detection capabilities of the chemometric approach to ignitable liquid detection under conditions similar to those of a structure fire. Burn conditions were controlled by adjusting the type and volume of ignitable liquid used, the fuel load, ventilation, and the elapsed time of the burn. Samples collected from the large scale burns were analyzed using passive headspace adsorption with activated charcoal strips and carbon disulfide desorption of volatiles for analysis using gas chromatography-mass spectrometry.
ID: 031001398; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; 305] pages in various pagings.; Title from PDF title page (viewed June 4, 2013).; Thesis (M.S.)--University of Central Florida, 2011.; Includes bibliographical references.
M.S.
Masters
Chemistry
Sciences
Forensic Science; Forensic Analysis Track

Pattern recognition is a term that can be used to cover various stages of the investigation of characterising data sets including contributing to problem formulation and data collection through to discrimination, assessment and interpretation of results. Chemometrics techniques and Artificial Neural Networks (ANNs) are pattern recognition techniques commonly used to visualise and gather useful information from multidimensional datasets i.e. datasets with n-samples with m- variables. Of the many chemometric techniques available, Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) are the most commonly used in the evaluation of dataset(s) generated from the analysis of samples which have relevance to forensic science. By contrast, Artificial Neural Networks (ANNs) and in particular Self Organising Feature Maps (SOFM) and Multi Layer Perceptron (MLP) have had limited application in forensic science eventhough these pattern recognition techniques have been known for almost 30 years. This study focuses on the applicability of the Artificial Neural Networks (ANNs) to specific datasets of forensic science interest and compares these with 'conventional' PCA and HCA techniques. Datasets generated from the analysis of wax based products and lighter fuels were used. The wax based product data set contained information obtained from Thin Layer Chromatography (TLC), Microspectrophotometry (MSP), Ultra-Violet and Visible Spectroscopy (UV/Vis) and Gas Chromatography with Flame Ionisation Detector (GC-FID) analysis of a variety of products from multiple sources where discrimination by brand was the objective. The data provided for the lighter fuel samples was obtained from analysis of a number of brands, both unevaporated and evaporated by Gas Chromatography-Mass Spectroscopy (GC-MS) and the objective was to discriminate the samples by brand as well as link degraded samples from the same brand together. The wax based product analysis provided simple, straight forward data whilst the lighter fuel analysis provided a more complicated and challenging dataset to investigate in terms of facilitating sample discrimination and/or linkage. In all cases, the 'conventional' Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) failed to provide any meaningful discrimination of the samples by product type regardless of the nature of the datasets. In contrast, the Artificial Neural Networks (ANNs) techniques provided full discrimination of the samples by product type even when the samples had undergone considerable ageing and weathering. This work has demonstrated the potential use of Self Organising Feature Maps (SOFM) and Multi Layer Perceptron (MLP) to datasets of forensic science relevance. The findings of this work provide avenues for further exploration of Artificial Neural Networks (ANNs) in forensic science.

L’identification des auteurs d’incendies criminels où un accélérant a été utilisé demeure à ce jour un domaine de recherche en développement. Les traces biologiques reines pour l’identification de personnes comme l’ADN et les traces papillaires sont généralement détruites, donc rarement recherchées. Pourtant, lier l’auteur des faits au lieu de l’incendie est un réel besoin. Ce lien pourrait être établi par l’inférence de source des traces d’accélérant détectées sur les lieux avec une source potentielle souvent amenée par l’enquête comme des objets saisis en possession du suspect (vêtements), un jerrican ou encore des prélèvements effectués sur ses mains. Dès lors, la question qui se pose consiste à déterminer si les traces d’accélérant détectées sur les lieux et les traces détectées sur l’élément de comparaison partagent une source commune. Ainsi, l’inférence de source de l’accélérant constitue une alternative au manque de traces matérielles de sorte à fournir des éléments de preuve à la suite d’un incendie volontaire. En ce sens, cette recherche propose une approche chimiométrique non ciblée pour l’inférence de source de liquides inflammables en science forensique. Cette approche a été appliquée à un échantillonnage conséquent d’essences non altérées et à un échantillonnage réduit d’essences altérées de 0 à 99% par évaporation et par combustion. L’évaluation des résultats a validé l’hypothèse selon laquelle il est possible de lier des échantillons d’essences altérés ou non, par évaporation ou combustion, indépendamment du mode et du degré d’altération
The identification of arsonists when an accelerant was used is still a challenging and ongoing research area. Golden standards in forensic human identification such as DNA and fingermarks are usually destroyed during the fire, hence not often looked for. It is yet obvious that the need to link the perpetrator to the arson site exists. This link could be made through a source inference process of the traces of an accelerant detected on site. These traces could be compared with a potential source often brought by the police investigation such as seized items in possession of a suspect (clothes), a jerrican or even hand sampling. Thenceforward, the question arising would be to determine if the traces of an accelerant from unknown source share a common source with the seized item. Thus, the source inference of accelerants constitutes an alternative to the lack of material traces in order to provide evidence in arson cases. To tackle this question, the present research proposes an untargeted chemometric approach for the source inference of ignitable liquids in forensic science. This approach was applied to a large dataset of unaltered gasoline samples and to a reduced one of altered samples by evaporation and combustion between 0 and 99%. The evaluation of results shows that it is possible to link gasoline samples altered or not by evaporation and combustion independently of the alteration mode and degree

Master’s thesis deals with a determination problem of ignitable liquids from fire debris. The aim of this work is to introduce the properties of used fire accelerants and to give an overview and evaluation of the various techniques which can be conducive to the fire investigator. Determination of fire accelerants from fire debris was made by the technique of solid phase microextraction (SPME) with subsequent chemical analysis by GC/MS. Based on the chromatographic results were established the target compounds and reconstructed ion chromatograms which are typical for some kinds of flammable liquids. There were used gasoline, diesel, kerosene and technical gasoline (white spirit) as the fire accelerants. This work also deals with the influence of interfering products in fire debris analysis, including their identification and characterization. Different kinds of substrates were burned, extracted and analyzed in order to identify all the interfering products that they may release.

The current methods for identifying ignitable liquid residues in fire debris are heavily based on the holistic, qualitative interpretation of chromatographic patterns with the mass spectral identification of selected peaks. The identification of neat, unweathered ignitable liquids according to ASTM 1618 using these methods is relatively straightforward for the trained analyst. The challenges in fire debris analysis arise with phenomena such as evaporation, substrate interference, and biodegradation. These phenomena result in alterations of chromatographic patterns which can lead to misclassifications or false negatives. The biodegradation of ignitable liquids is generally known to be more complex than evaporation [20], and proceeds in a manner that is dependent on numerous factors such as: composition of the petroleum product/ignitable liquid, structure of the hydrocarbon compound, soil type, bacterial community, the type of microbial metabolism that is occurring, and the environmental conditions surrounding in the sample. While nothing can be done to prevent the biodegradation, continued research on biodegraded ignitable liquids and the characterization of the trends observed may be able to provide insight into how an analyst can identify a biodegraded ignitable liquid residue. This research utilized normalized abundance values of select ions from pre-existing gas chromatography-mass spectrometry (GC-MS) data on samples from three different gasoline and diesel biodegradation studies. A total of 18 ions were selected to indicate the presence of six hydrocarbon classes (three each for alkanes, aromatics, cycloalkanes, naphthalenes, indanes, and adamantanes) based on them being either base peaks or high abundance peaks within the electron impact mass spectra of compounds within that hydrocarbon class. The loss of ion abundance over the degradation periods was assessed by creating scatter plots and performing simple linear regression analyses. Coefficient of determination values, the standard error of the estimate, the slope, and the slope error of the best fit line were assessed to draw conclusions regarding which classes exhibited desirable characteristics, relative to the other classes, such as a linear degradation, low variation in abundance within the sampling days, and a slow rate of abundance loss over the degradation period. Additional analyses included two-way analysis of the variance (ANOVA), to assess the effects of time as well as different soil type on the degradation of the hydrocarbons, stepwise multinomial logistic regressions to identify which classes were the best predictors of the type of ignitable liquid, and one-way ANOVAs to determine where the differences in the ratios of hydrocarbon classes existed within each of the ignitable liquids, as well as between the two liquids. Hydrocarbon classes identified as exhibiting characteristics such as slow and/or reliable rates of abundance loss during biodegradation are thought of as desirable for future validation studies, where specific ranges of hydrocarbon class abundance(s) may be used to identify the presence of a biodegraded ignitable liquid. Classes of hydrocarbons that have experienced biodegradation that maintain an abundance close to that of a neat, non degraded counterpart, or that reliably degrade and have predictable abundance levels given a particular period of degradation, would be instrumental in determining whether or not an unknown sample contains an ignitable liquid residue. It is the hope that these assessments will not only provide helpful information to future researchers in the field of fire debris analysis, but that they will create interest in the quantitative, statistical assessment of ignitable liquid data for detection and identification purposes.

Gasoline is a substance commonly encountered in forensic settings. Unfortunately, gasoline is an easily obtainable ignitable liquid that arsonists commonly use to initiate or expedite the spread of an intentionally set fire. Fires claim the lives of many people each year in addition to causing widespread property damage. Many fire scene investigations result in charges of arson, which has the legal connotation of a committed crime. For this reason, extensive analysis and investigation must be undertaken before any suspected arson scene is deemed an actual case of arson. Although ignitable liquids, including gasoline, may be present at the scene of a fire, it does not necessarily mean they were intentionally used as accelerants. An accelerant is a fuel used to initiate a fire. These realities, in addition to several other factors, demonstrate why a rapid, reliable, gasoline analysis method is crucial to forensic applications. In this thesis, direct analysis in real time – mass spectrometry (DART-MS) is evaluated as a potential method that could better identify, distinguish and classify gasoline brands from one another. Techniques such as DART-MS could enable forensic laboratories to better identify questioned gasoline samples. Many ignitable liquids share similar chemical properties, and forensically relevant evidence is often obtained from a crime scene in less than favorable conditions. Fire debris can encompass various materials, including burnt carpet, flooring, items of furniture and clothing, among others. If gasoline was used as an accelerant, it may be present in trace amounts after the termination of the fire. Materials submitted for laboratory analysis may be substrates with compositions that have components similar to those found in some ignitable liquids. These are just a few of the potential obstacles that could be encountered with analyzing fire debris in a forensic setting. Traditionally, gas chromatography – mass spectrometry (GC-MS) methods are utilized for gasoline analysis in the criminal laboratory setting. While traditional GC-MS methods are sensitive and able to classify samples as gasoline, they are time consuming in terms of both sample preparation and analysis. Additionally, they do not generate differential mass spectral data based on the brand of gasoline. Conversely, gasoline analysis in this research, utilizing the DART-MS method, demonstrated that five different brands of gasoline could be distinguished from one another both by visual examination of mass spectra and with methods of chemometric analysis. Advantageously, the DART-MS method, an ambient ionization technique, requires little sample preparation and a rapid sample analysis time, which could drastically increase the throughput of standard sample analysis with further method development. The goals and objectives of this research were to optimize the DART-MS parameters for gasoline analysis, determine if DART-MS analysis could distinguish gasoline by brand, develop chemometric models to appropriately classify gasoline samples, and finally lay groundwork for future studies that could further develop a more efficient and discriminating DART-MS gasoline analysis method for forensic casework. Each brand of gasoline was observed to have a chemical attribute signature (CAS) consisting of not only low-mass ions, but also a variety of high-mass ions not usually observed with gasoline samples analyzed by GC-MS. Although variables including season, storage time, dilution and age of the gasoline were observed to contribute to the resulting mass spectral data, once the mass spectra are better understood, they could offer even more discriminating power between samples than simple analysis of the gasoline brand. In this research, DART-MS parameters were first optimized for gasoline analysis. Subsequently, the five acquired brands of gasoline: Shell, Sunoco, Irving, Cumberland Farms and Gulf, were analyzed both undiluted (or neat) and diluted utilizing the DART-MS analysis method. GC-MS data was generated and analyzed to show comparisons. After analyzing the data generated by both approaches, it was apparent that the DART-MS method could generate CASs based on the gasoline brand and offer a degree of differentiation that traditional GC-MS does not. Additional chemometric analyses utilizing principle component analysis (PCA) and the construction of models with Analyze IQ Lab software verified that the gasoline brands were distinguishable when samples were analyzed with this ambient ionization method. PCA plots of the neat gasoline demonstrated clustering based on brand. Additionally, models constructed from training samples generated from DART-MS analysis of the various brands were able to accurately classify gasoline samples as "yes" or "no" when a test set of gasoline was compared to all five brands. The lowest associated testing error rate for some of these models was 0%. However, additional analysis with greater sample sizes needs to be further carried out to more accurately evaluate this method of gasoline analysis and classification.

In Ontario, fire investigators from the Office of the Fire Marshal (OFM) are responsible for determining the origin and cause of suspicious fires. As part of the investigation, fire debris samples are collected from the scene and analyzed by the Centre of Forensic Sciences. The standard practice is to collect items that are porous, highly absorbent or adsorbent with high surface areas as they allow for better retention of the ignitable liquids. The evidence typically collected includes carpets, cardboards, soils, cloths and other items that have not been impinged by flame such as beneath baseboards. These samples are analyzed for the presence of ignitable liquid residues which may be evidence that an accelerant was used at the fire. When a body is recovered from a fire it can provide another source from which to collect samples for analysis. These samples can be especially helpful in instances where the fire generated an intense heat which may cause a loss of ignitable liquid residues from the fire debris. The tissue samples have a greater likelihood of still containing residues as the organs and body fluids can act as a shield protecting the residues from volatilization. The purpose of this study is to validate whether a victim was alive or deceased at the time a fire was intentionally set by detecting presence or absence of gasoline residues within their lungs and heart blood post fire. It was hypothesized that only when a victim was alive and performing respiration would sufficient gasoline vapours enter the airways and bloodstream for detection postmortem. Contamination becomes a significant issue when these samples are collected at autopsy and this study aimed to determine the accuracy with which a gasoline signature can be interpreted following the collection and analysis of lung tissue and heart blood. Pig (Sus domesticus) carcasses were chosen as acceptable analogues for humans in this study. The experiments involved anaesthetizing a pig (with Animal Ethics Approval), exposing the pig to gasoline vapours for 10 minutes, and then euthanizing it. The carcass was clothed with a cotton t-shirt and placed in a house where additional gasoline was poured onto it. The house also contained two additional clothed pig carcasses which did not inhale gasoline vapours; one with gasoline poured directly onto it and the other with no gasoline exposure (negative control). Thermocouples were placed under each carcass and in the centre of each room at ceiling and floor level to record the temperature. The house was set ablaze and monitored by a volunteer fire service. After the fire had reached V flashover and was suppressed, the carcasses were collected and their lungs and heart blood excised at a necropsy. The lungs and heart blood were then placed into glass mason jars following the OFM protocol. The headspace from each sample was analyzed by thermal desorption-gas chromatography-mass spectroscopy to determine the presence or absence of a gasoline signature. Two full scale house fires were conducted in order to obtain three replicates. The results showed that only the lungs and heart blood from the pig that inhaled gasoline contained gasoline residues. This indicates that it is possible to determine a victim’s status at the time of the fire based on the detection of gasoline in the lungs and/or heart blood. It was also concluded that contamination of samples during an autopsy can be minimized by changing gloves before handling the internal tissues. The thermal data showed that the bodies act as an insulator and protects the underside as the temperatures under the carcasses did not exceed 30⁰C while the room reached over 900⁰C at the first full scale house fire. These results will impact the forensic community by demonstrating the importance of analyzing a deceased victim’s internal tissues for ignitable liquid residues post fire as they may provide evidence of an intentionally set fire as well as providing information about the victim’s status when a fire was started. These findings will have a direct impact to the OFM as additional evidence can be obtained by completing internal tissue analysis. This will intern impact the Centre of Forensic Science (CFS) as it confirms the importance of analyzing internal tissues in order to provide results to fire investigators. Finally these findings should be used to implement new protocols at the Coroner’s Office so contamination can be minimized during fire autopsies and accurate samples are collected and sent to the CFS for analysis.
UOIT

Indiana University-Purdue University Indianapolis (IUPUI)
Organic-rich substrates such as soil provide an excellent carbon source for bacteria. However, hydrocarbons such as those found in various ignitable liquids can also serve as a source of carbon to support bacterial growth. This is problematic for fire debris analysis as samples may be stored at room temperature for extended periods before they are analyzed due to case backlog. As a result, selective loss of key components due to bacterial metabolism can make identifying and classifying ignitable liquid residues by their chemical composition and boiling point range very difficult. The ultimate goal of this project is to preserve ignitable liquid residues against microbial degradation as efficiently and quickly as possible. Field and laboratory studies were conducted to monitor microbial degradation of gasoline and other ignitable liquids in soil samples. In addition to monitoring degradation in potting soil, as a worst case scenario, the effect of soil type and season were also studied. The effect of microbial action was also compared to the effect of weathering by evaporation (under nitrogen in the laboratory and by the passive headspace analysis of the glass fragments from the incendiary devices in the field studies). All studies showed that microbial degradation resulted in the significant loss of n-alkanes and lesser substituted alkylbenzenes predominantly and quickly, while more highly substituted alkanes and aromatics were not significantly affected. Additionally, the residential soil during the fall season showed the most significant loss of these compounds over the course of 30 days. To combat this problem, a chemical solution is to be immediately applied to the samples as they are collected. Various household and commercial products were tested for their efficacy at low concentrations to eliminate all living bacteria in the soil. Triclosan (2% (w/v) in NaOH) proved to be the most effective at preserving ignitable liquid residues for at least 30 days.

The detection and identification of the oxygenated class of ignitable liquids is a complex issue for the fire debris analyst. The oxygenated compounds are difficult to recover using traditional analytical techniques since their chemical characteristics are vastly different from those of the petroleum products that compose the majority of the ignitable liquid classes. Previous research has demonstrated that the use of zeolite 13X as an adsorbent in heated passive headspace concentration provides increased recovery of oxygenated compounds in comparison to the conventional activated charcoal adsorbent. This hypothesis was further tested in this work using more realistic casework scenarios. Various carpet, carpet padding and wood types were utilized in a number of burn conditions in order to determine if any substrate interferences were present; as well as to monitor the recovery of oxygenated compounds from these substrates using the proposed zeolite extraction method. The substrates explored did not contribute significant background interference to complicate the identification of the oxygenated compounds. In addition, small volumes of the oxygenated ignitable liquids were easily recovered and identified from all burn states using the zeolite method. A dual-mode extraction with both zeolites and activated charcoal strips as adsorbents was utilized with mixtures of oxygenated compounds and petroleum products to determine if a variety of ignitable liquid classes could be detected and identified in the presence of a variety of substrate matrices within a single extraction protocol. The dual-mode extraction showed that both the oxygenated compounds and petroleum products could be detected and identified using a single extraction protocol in the presence of various substrate matrices. Lastly, an experiment was devised to compare the recovery of the oxygenated compounds using various total available surface areas of both zeolites and activated charcoal strips in order to determine which adsorbent exhibits a greater recovery when all other experimental conditions remain constant. When the surface areas were equalized between the zeolites and activated charcoal strips, the activated charcoal exhibited a greater recovery of the oxygenated compounds. However, the cost effectiveness of the zeolites allows for a greater amount of zeolite beads to be used in order to achieve the same recovery as the activated charcoal strips for a much lower price. Therefore, the findings from this work, in combination with previous research, continue to support the use of zeolite 13X as an alternative adsorbent for the recovery of oxygenated ignitable liquids from fire debris evidence.

Identification of ignitable liquids in fire debris analysis using pattern recognition is an important step in determining the nature of a suspicious fire. Complex mixtures that make up ignitable liquids are susceptible to microbial degradation when fire debris evidence is presented in the form of soil. Microbial degradation results in a selective metabolism of certain classes of compounds required for identification of an ignitable liquid. Various ignitable liquids that may be used to initiate or propagate a fire contain different classes of organic compounds. These include normal alkanes, branched alkanes, cycloalkanes, aromatics, terpenes, and others. In this work, microbial degradation of nine ignitable liquids in soil was evaluated over a period of twenty-six days. The degradation of aromatic compounds in gasoline was faster with toluene and C2-alkylbenzenes than in C3-alkylbenzenes. However, the overall loss of aromatics made gasoline chromatographically unidentifiable. The complete loss of n-alkanes in medium and petroleum distillates resulted in patterns that resembled naphthenic-paraffinic products. Normal alkanes were more susceptible to microbial degradation than isoalkanes, which was specifically demonstrated in medium and heavy petroleum distillates. In diesel, pristane and phytane remained prominent in comparison to the normally prevalent n-alkanes, which could no longer be detected post-degradation. The degradation of isoalkanes and cycloalkanes was evaluated in a naphthenic-paraffinic product. Isoalkanes were degraded significantly faster than cycloalkanes. The remaining peaks in the naphthenic-paraffinic pattern consisted solely of cycloalkane compounds, and could no longer be classified as a naphthenic-paraffinic product. The terpene compounds in turpentine were also observed to be susceptible to degradation by microorganisms. The loss of !-pinene, limonene, and camphene was significantly noticeable in comparison to other terpene compounds, such as 1,4-cineole. Microbial biodegradation in different soil types was investigated. The difference in soil texture can affect the rate of metabolism of ignitable liquids due to the variance of available oxygen, nutrients and mobility of the microbial population. The degradation of isoalkanes, cycloalkanes, aromatics and heavier normal alkanes was faster in clay, whereas normal alkanes of lower molecular weight were degraded more readily in sand. There has been no explanation of this occurrence within the scientific literature, however it could be hypothesized that the difference in microbial flora and water saturation levels could affect the selective degradation between the two soil types. Fire debris evidence is often stored for long periods of time before analysis due to case backlogs. The storage condition of arson-related soil samples is a sensitive subject. If evidence, containing soil, is stored at room temperature, petroleum compounds in any ignitable liquid residues that are present will be degraded within a week. Therefore, it is important to freeze or refrigerate soil samples. The storage of both refrigerated and frozen soil samples containing gasoline were evaluated over six months. Less than 6% of the aromatic compounds distinctive of gasoline remained when stored at 5 °C, while minimal change was observed in the same compounds when stored at -15 °C. Microbial degradation of petroleum-based ignitable liquids is advantageous from the environmental perspective. However, within the forensic community the effect of microbial action could lead to misclassification or inability to identify the presence of an ignitable liquid in fire debris evidence.

In fire debris analysis, substrate contribution refers to compounds present within the material collected that can interfere with the instrumental detection of ignitable liquids or contribute petroleum or alcohol-based compounds, which may complicate the interpretation. The concept of substrate contribution was brought to light by "The petroleum-laced background" by Lentini et al. focusing on commercial products (e.g. tennis shoes, magazines, etc.), the publication successfully illustrated that these products can produce chromatograms similar to those generated by the presence of petroleum-based ignitable liquids (ILs). As a result, Lentini et al. demonstrated that fire debris analysts can identify the presence of ignitable liquids without realizing the compounds in question might be the result of the manufacturing processes, and are inherent to the substrate in question. Therefore, the findings may or may not be probative. Gasoline is easily accessible and is frequently used by arsonists. As such, fire debris analysis focuses primarily on petroleum-based compounds. However, oxygenated solvents, which encompass all oxygen-containing compounds as defined by the American Society for Testing and Materials (ASTM) classification scheme, can also be used in an arson event. Despite the potential to be used as ILs, little is known regarding the recovery of these compounds. Previous thesis projects from the Biomedical Forensic Sciences program at Boston University School of Medicine explored and optimized the use of zeolites in recovering low molecular weight oxygenated ignitable liquids. An isothermal gas chromatography/mass spectrometry (GC/MS) method was also developed to detect these oxygenated ILs. The results from these projects show that zeolites have the potential to be used in forensic casework. Inspired by previous publications and thesis research, the goal of this project was to first develop a reference library on substrate contribution from oxygenates (e.g. ethanol, isopropanol and acetone) present in commercial products using the isothermal GC/MS methods. The development of this reference library included a specific interest in wood treatment products, considering wood is one of the most commonly submitted fire debris materials. The second stage involved an attempt at evaluating extraction efficiencies of activated charcoal strip and zeolites. The results of this project suggested that automotive and food products examined contained only acetone and ethanol respectively, while the variety of oxygenates found in household and personal care products indicated further analysis of additional products in these categories would be beneficial. Moreover, the results also reaffirmed zeolites' role in recovering oxygenated ILs in a controlled testing environment using KimWipes as a non-contributing substrate. However, the instrumental method required some modifications, as there was partial separation between ethanol and acetone. The results from applying products onto wooden blocks suggested that activated charcoal strips recovered more oxygenates than zeolites. This unexpected result prompted an investigation into the existing extraction parameters. The investigation suggested that the wooden blocks themselves were responsible for the unexpected recovery results, and future studies would be needed to understand if this recovery was substrate-specific.

碩士
中央警察大學
鑑識科學研究所
100
Arson is commonly encountered in fire cases. The physical evidence such as biological samples and fingerprints is frequently destroyed resulting from fire burning and the extinguishing water. In general, identifying ignitable liquid residuses (ILR) in fire debris samples plays the key role in investigating the fire couse. The purpose of this study is focused on the identification of ILR from arson debris samples by the E-nose and the gas chromatography-isotope ratio mass spectrometry (GC-IRMS). The E-nose is used to classify ILR in the preliminary stage, and GC-IRMS is futher used to distinguish different classes of gasolines. The activated charcoal strip is adopted as an adsorbent material to extract ILR from the headspace in the sample container, then it is eluted by using carbon disulfide (CS2). The amount of 30μL for each ignitable liquid is spiked on a concrete substrate which is placed into a metal can with an activated charcoal strip. The container is heat under 85℃ for 24 h. The charcoal strip is eluted with 1mL of CS2 solvent, and 1μL of the eluted solution is injected into E-nose and GC-IRMS respectively. The optimal conditions for the E-nose approach are evaluated prior to the further analysis. The principal component analysis (PCA) builted in E-nose is evaluated for the classification of 18 ignitable liquids based on the two sets of chromatographic results. The degree of evaporation (fresh, 25％, 50％, 75％, and 90％) of ignitable liquids can be profiled by PCA analysis. Distinguishing between examples within gasoline class is conducted by the comparsons of δ13C values in GC-IRMS approach. In the results of this study, the E-nose approach is used for the classification of 18 kinds of ignitable liquids by both visual comparison of total ion chromatograms and PCA protocal. The degree of evaporation of ignitable liquids can also be recognized by E-nose analysis assisted with PCA approach. Resulting data from GC-IRMS analysis indicate that gasolines with different brands can be easily distinguished. However, it is difficult to distinguish different classes of gasolines of the same brand. The GC-IRMS method still has a highly distinguishing power in distinguishing different classess of gasoline of the same brand if sufficient parameters have been selected.