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Addendum To Automated Data Analysis Of Fire Debris Samples Using Gas Chromatography Mass Spectrometry And Macro Programming
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Book Synopsis Addendum to Automated Data Analysis of Fire Debris Samples Using Gas Chromatography-mass Spectrometry and Macro Programming by : Jack Nowicki
Download or read book Addendum to Automated Data Analysis of Fire Debris Samples Using Gas Chromatography-mass Spectrometry and Macro Programming written by Jack Nowicki and published by . This book was released on 1994 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Automated Data Analysis of Fire Debris Samples Using Gas Chromatography-mass Spectrometry and Macro Programming by : Jack Nowicki
Download or read book Automated Data Analysis of Fire Debris Samples Using Gas Chromatography-mass Spectrometry and Macro Programming written by Jack Nowicki and published by . This book was released on 1993 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific Evidence by : Paul C. Giannelli
Download or read book Scientific Evidence written by Paul C. Giannelli and published by Lexis Law Publishing (Va). This book was released on 1999 with total page 920 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis of Fire Debris Samples by Gas Chromatography/mass Spectrometry (GC-MS). by : Jack Nowicki
Download or read book Analysis of Fire Debris Samples by Gas Chromatography/mass Spectrometry (GC-MS). written by Jack Nowicki and published by . This book was released on 1991 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis of Fire Debris Samples by Gas Chromatography/mass Spectrometry (GC-MS). by : Jack Nowicki
Download or read book Analysis of Fire Debris Samples by Gas Chromatography/mass Spectrometry (GC-MS). written by Jack Nowicki and published by . This book was released on 1991 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Current Law Index written by and published by . This book was released on 1996 with total page 1242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis GC/MS Data from Fire Debris Samples by : (Jack) Wallace, JR.
Download or read book GC/MS Data from Fire Debris Samples written by (Jack) Wallace, JR. and published by . This book was released on 1999 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mass chromatography is currently being adapted by many forensic laboratories as the preferred approach for interpreting GC/MS data from fire debris samples. This paper first describes software approaches for minimizing interferences and for facilitating the identification of petroleum liquids when using this approach. Next, guidelines are developed for recognizing chromatographic distortion that often occurs when petroleum liquids are recovered using the popular solid adsorption/elution method. It is seen that for a given petroleum liquid, paraffinic:aromatic ratios can vary eight fold depending on the recovery conditions and sample concentration. Finally, the application of these software tools and guidelines to case samples is illustrated, and an approach for categorizing an exemplar collection on the basis of qualitative features and peak height ratios is demonstrated.
Book Synopsis Determining the Presence of an Ignitable Liquid Residue in Fire Debris Samples Utilizing Target Factor Analysis by : Kelly M. McHugh
Download or read book Determining the Presence of an Ignitable Liquid Residue in Fire Debris Samples Utilizing Target Factor Analysis written by Kelly M. McHugh and published by . This book was released on 2010 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis GC/MS Data from Fire Debris Samples by : John R. Wallace
Download or read book GC/MS Data from Fire Debris Samples written by John R. Wallace and published by . This book was released on 1999 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Survey on the Interpretive GC/MS Analysis of Fire Debris by : Anthony Thomas Parks
Download or read book A Survey on the Interpretive GC/MS Analysis of Fire Debris written by Anthony Thomas Parks and published by . This book was released on 2018 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: The practice of arson analysis in a forensic science laboratory is based upon detecting the presence of ignitable liquids. If an ignitable liquid is present, it is suggestive of arson; if no ignitable liquid is found an arson claim is more difficult to assert. Ignitable liquids are detected using gas chromatography coupled with mass spectrometry. Instrumental results from a GC/MS can display components of an ignitable liquid but an analyst needs to make the final decision. Even with correct instrumentation and suggested guidelines, ignitable liquid analysis can be subjective and based upon the analysts' education and experience. To better understand the interpretive practices of the fire debris analysis community, a survey consisting of reference samples, mixture standards, and multiple unknowns was created in consultation with the Los Angeles Police Department Arson Unit. The samples consisted of different substrates with varying classes and volumes of ignitable liquid. They were created using a destructive distillation method first developed by the State of Florida Bureau of Forensic Fire and Explosives Analysis. Extraction of the samples was completed using a carbon strip to perform passive headspace absorption following the ASTM E 1412 method. The samples were analyzed with a GC/MS following National Commission on Forensic Science parameters. To maintain confidentiality, participant responses are stripped of identifiers and the results of the survey, details about the procedure, and discussions will be presented.
Book Synopsis Gas Chromatography Coupled with Ion Trap Mass Spectrometry (GC-MS and GC-MS-MS) - for Arson Debris Analysis by : Betty-Jane De Vos
Download or read book Gas Chromatography Coupled with Ion Trap Mass Spectrometry (GC-MS and GC-MS-MS) - for Arson Debris Analysis written by Betty-Jane De Vos and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas chromatography - mass spectrometry (GC-MS) is an established instrumental technique used for the analysis of fire debris for accelerant detection. However, matrix problems, such as pyrolysis product interference, are still encountered. These interferences often lead to inconclusive interpretation of the chromatographic results. This study describes methods for analysing arson accelerants using gas chromatography coupled with ion trap mass spectrometry. The latter technique lends itself to both conventional (GC-MS) as well as tandem mass spectrometry (GC-MS-MS). Since petrol (gasoline) is one of the more common distillate blends used by arsonists, especially in South Africa, the identification of petrol in fire debris samples was investigated. In order to overcome pyrolysis product interference and improve detection selectivity of the aromatic hydrocarbons in petrol residues, tandem mass spectrometry was used in combination with capillary gas chromatography. The added parameter of the third dimension of selectivity proved to be superior to conventional GC-MS in obtaining characteristic aromatic hydrocarbon profiles for petrol without interference from pyrolysis artefacts.
Book Synopsis Classification of Ground-truth Fire Debris Samples Using Neural Networks by : Nicholas Alan Thurn
Download or read book Classification of Ground-truth Fire Debris Samples Using Neural Networks written by Nicholas Alan Thurn and published by . This book was released on 2021 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fire debris samples are currently analyzed according to ASTM E1618-19, which is the “Standard Test Method for Ignitable Liquid Residues in Extracts from Fire Debris Samples by Gas Chromatography-Mass Spectrometry.” This method requires that an analyst make a visual comparison to an appropriate reference sample using the total ion and the extracted ion chromatograms. The analyst then provides an opinion about whether an ignitable liquid residue is present in the sample. The method is inherently subjective due to the visual interpretation that is needed. In order to automate this process, this work uses neural networks and a subset of the ions specified in ASTM E1618-19, which represent many of the compounds present in ignitable liquids, to cluster and classify ground-truth fire debris samples. The first part of this work demonstrates that these ions provide sufficient information to allow for the clustering of the ignitable liquid classes defined in ASTM E1618-19 and substate pyrolysis extracts using self-organizing maps. Classification using self-organizing maps resulted in a 96% correct classification rate on an independent test set. The latter portion of this work demonstrates the use of the ASTM ions in conjunction with feedforward neural networks to evaluate laboratory prepared ground-truth fire debris samples. An optimal neural network model was selected from a set of candidate models that were trained on in-silico fire debris samples. Receiver operating characteristic curves were used to select an optimal decision threshold for classifying a fire debris sample as positive or negative for ignitable liquid residues using a false positive to false negative cost ratio of 10. The use of this threshold for classification resulted in a somewhat conservative model with a true positive rate of 0.59 and a false positive rate of 0.07 for a set of laboratory-generated ground-truth fire debris samples.
Book Synopsis Automated Processing and Analysis of Gas Chromatography/mass Spectrometry Screening Data by : Jonathan James Hitchcock
Download or read book Automated Processing and Analysis of Gas Chromatography/mass Spectrometry Screening Data written by Jonathan James Hitchcock and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The work presented is a substantial addition to the established methods of analysing the data generated by gas chromatography and low-resolution mass spectrometry. It has applications where these techniques are used on a large scale for screening complex mixtures, including urine samples for sports drug surveillance. The analysis of such data is usually automated to detect peaks in the chromatograms and to search a library of mass spectra of banned or unwanted substances. The mass spectra are usually not exactly the same as those in the library, so to avoid false negatives the search must report many doubtful matches. Nearly all the samples in this type of screening are actually negative, so the process of checking the results is tedious and time-consuming. A novel method, called scaled subtraction, takes each scan from the test sample and subtracts a mass spectrum taken from a second similar sample. The aim is that the signal from any substance common to the two samples will be eliminated. Provided that the second sample does not contain the specified substances, any which are present in the first sample can be more easily detected in the subtracted data. The spectrum being subtracted is automatically scaled to allow for compounds that are common to both samples but with different concentrations. Scaled subtraction is implemented as part of a systematic approach to preprocessing the data. This includes a new spectrum-based alignment method that is able to precisely adjust the retention times so that corresponding scans of the second sample can be chosen for the subtraction. This approach includes the selection of samples based on their chromatograms. For this, new measures of similarity or dissimilarity are defined. The thesis presents the theoretical foundation for such measures based on mass spectral similarity. A new type of difference plot can highlight significant differences. The approach has been tested, with the encouraging result that there are less than half as many false matches compared with when the library search is applied to the original data. True matches of compounds of interest are still reported by the library search of the subtracted data.
Book Synopsis Chemometric Applications to a Complex Classification Problem by : Erin Elizabeth Waddell
Download or read book Chemometric Applications to a Complex Classification Problem written by Erin Elizabeth Waddell and published by . This book was released on 2013 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fire debris analysis currently relies on visual pattern recognition of the total ion chromatograms, extracted ion profiles, and target compound chromatograms to identify the presence of an ignitable liquid. This procedure is described in the ASTM International E1618-10 standard method. For large data sets, this methodology can be time consuming and is a subjective method, the accuracy of which is dependent upon the skill and experience of the analyst. This research aimed to develop an automated classification method for large data sets and investigated the use of the total ion spectrum (TIS). The TIS is calculated by taking an average mass spectrum across the entire chromatographic range and has been shown to contain sufficient information content for the identification of ignitable liquids. The TIS of ignitable liquids and substrates were compiled into model data sets. Substrates are defined as common building materials and household furnishings that are typically found at the scene of a fire and are, therefore, present in fire debris samples. Fire debris samples were also used which were obtained from laboratory-scale and large-scale burns. An automated classification method was developed using computational software, that was written in-house. Within this method, a multi-step classification scheme was used to detect ignitable liquid residues in fire debris samples and assign these to the classes defined in ASTM E1618-10. Classifications were made using linear discriminant analysis, quadratic discriminant analysis (QDA), and soft independent modeling of class analogy (SIMCA). The model data sets were tested by cross-validation and used to classify fire debris samples. Correct classification rates were calculated for each data set. Classifier performance metrics were also calculated for the first step of the classification scheme which included false positive rates, true positive rates, and the precision of the method. The first step, which determines a sample to be positive or negative for ignitable liquid residue, is arguably the most important in the forensic application. Overall, the highest correct classification rates were achieved using QDA for the first step of the scheme and SIMCA for the remaining steps. In the first step of the classification scheme, correct classification rates of 95.3% and 89.2% were obtained using QDA to classify the cross-validation test set and fire debris samples, respectively. For this step, the cross-validation test set resulted in a true positive rate of 96.2%, a false positive rate of 9.3%, and a precision of 98.2%. The fire debris data set had a true positive rate of 82.9%, a false positive rate of 1.3%, and a precision of 99.0%. Correct classifications rates of 100% were achieved for both data sets in the majority of the remaining steps which used SIMCA for classification. The lowest correct classification rate, 69.2%, was obtained for the fire debris samples in one of the final steps in the classification scheme. In this research, the first statistically valid error rates for fire debris analysis have been developed through cross-validation of large data sets. The fire debris analyst can use the automated method as a tool for detecting and classifying ignitable liquid residues in fire debris samples. The error rates reduce the subjectivity associated with the current methods and provide a level of confidence in sample classification that does not currently exist in forensic fire debris analysis.
Book Synopsis Development of a Computational Application to Aid with Chemometric and Forensic Analysis of Fire Debris Samples by : Michelle Anne Corbally
Download or read book Development of a Computational Application to Aid with Chemometric and Forensic Analysis of Fire Debris Samples written by Michelle Anne Corbally and published by . This book was released on 2022 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fire debris analysis is a forensic science discipline that determines if an ignitable liquid residue is present or absent in a fire debris sample. Currently, fire debris analysis results in categorical statements based on qualitative data, not the quantitative evidentiary value of data. The purpose of this research was to develop a novel software application to aid fire debris analysts in the identification and classification of ignitable liquid residues that are found in fire debris samples. The developed application uses target factor analysis (TFA) and Pearson correlation for compound identification in gas chromatograms using mass spectral comparison and allows for visual comparison of unknown fire debris samples chromatograms to ignitable liquid references from the National Center for Forensic Science (NCFS) Ignitable Liquid Reference Collection (ILRC). Frequencies of occurrences were calculated for each of 295 compounds from the NCFS compound library through compound identification of ignitable liquid, substrate, and fire debris samples using the novel computer application. The log-likelihood ratios of compounds determined to be within an optimal subset of best chromosomes determined using a genetic algorithm were used for calculating Naïve Bayes log-likelihood ratios for fire debris samples. Finally, self-organizing feature maps (SOFM), trained with in-silico total ion spectra data, were used to classify ground truth fire debris samples into American Society for Testing and Materials (ASTM) E1618-19 classes. Pearson correlation was then used to compare the total ion chromatograms of the classified fire debris samples were then compared to the in-silico total ion chromatograms located within the assigned SOFM node. The performance and validation of these models are discussed further in this dissertation.
Book Synopsis The Analysis of Fire Debris Samples by GC/MS/MS. by : D. A. Sutherland
Download or read book The Analysis of Fire Debris Samples by GC/MS/MS. written by D. A. Sutherland and published by . This book was released on 1997 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Identifying Ignitable Liquids in Fire Debris by : Jeanet Hendrikse
Download or read book Identifying Ignitable Liquids in Fire Debris written by Jeanet Hendrikse and published by Academic Press. This book was released on 2015-10-05 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Identifying Ignitable Liquids in Fire Debris: A Guideline for Forensic Experts discusses and illustrates the characteristics of different ignitable liquid products. This guideline builds on the minimum criteria of the ignitable liquid classes defined in the internationally accepted standard ASTM E1618 Standard Test Method for Ignitable Liquid Residues in Extracts from Fire Debris Samples by Gas Chromatography-Mass Spectrometry. The volume provides information on the origin of the characteristics of these ignitable liquid products and provides a summary of characteristics to demonstrate a positive identification of the particular product class. Topics such as the term ignitable liquid, relevant guidelines for fire debris analysis, production processes of ignitable liquids, fire debris analysis methods, and interferences in fire debris analysis, are briefly discussed as these topics are essential for the understanding of the identification and classification of ignitable liquid residues in fire debris. Discusses the characteristics and variations in chemical composition of different classes of the ignitable liquid products defined by ASTM E1618:14 Covers the General Production Processes of Ignitable Liquid Products Includes a guide for the Identification of Ignitable Liquids in Fire Debris
