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DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY AND INTERNATIONAL FORENSIC RESEARCH INSTITUTE |
Elemental Analysis of Automotive Paint Samples by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and Paint and Glass by Laser Induced Breakdown Spectroscopy (LIBS)By: Andria Hobbs, Master of Science in Forensic Science (Awarded 2003)Glass and paints are frequently encountered forms of evidence submitted to forensic laboratories. This study has developed methods to complement commonly used techniques in a crime laboratory to better characterize these evidence materials for forensic purposes. Automotive paint samples have been analyzed by LA-ICP-MS to determine the discrimination power of the technique. Optimization and validation studies were first conducted, including a homogeneity study. Automotive paints indistinguishable by common methods have been analyzed in order to determine the forensic utility of LA-ICP-MS and have shown that LA-ICP-MS can distinguish between those samples. Additionally, household paint samples known to contain high levels of lead were analyzed by the developed LIBS technique. For glass samples, LIBS was able to classify the glass by type and to further distinguish 51% of the containers. These techniques are now available for forensic scientists for the analysis of automotive paint samples and glass samples. Oral Presentations At Scientific Meetings
Scientific Papers, Book Chapters And Other Publications
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Identification of Gamma-HydroxyButyrate (GHB) and
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Development of Microsatellite Loci in Cannabis Sativa L.By: Hussain AlGhanim, Master of Science in Forensic Science (Awarded 2003)Microsatellite DNA or simple sequence repeat (SSR) provide an ideal tool for assessing the genetic diversity of plants due to their high information content, ease of genotyping, codominant and multiallelic nature, high discriminatory power, and reproducibility. Microsatellites have been used successfully in agricultural and breeding studies as well as in the analysis of natural population. Microsatellites are DNA sequences of four or fewer bases that are repeated in tandem arrays (i.e. ATATATATATATATATATAT). Such microsatellite sequences have been found randomly distributed throughout the genomes of all eukaryotes assayed except yeast. The highly polymorphic microsatellites have proved very useful in population genetics studies. This proposed work specifically aims to identify a number of microsatellite loci capable of capturing polymorphism among different Cannabis individuals. The microsatellite loci will be searched for in a systematic effort by marker enrichment technique, which consists of: 1) screening the extracted DNA of Cannabis sativa L. with specific repeat unit probes, 2) sequencing the positive clones, and 3) designing oligonucleotide primers on either side of the repeat region. It is felt that this information can be used to track marijuana growers and distribution networks as well as confirm (through comparisons akin to human DNA comparisons) the source of origin of individual plants. Therefore, this technique could be used by operational laboratories that have an interest in tracking marijuana sources through genetic data. |
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Elemental Analysis of Forensic Glass by ICP-MSBy: Shirly Montero, Ph.D.(Awarded 2002)The value of glass evidence in forensic investigations has been well established in a number of studies and publications. Measurements of physical and optical characteristics are widely used to compare recovered pieces to a known source. However, improvements in glass quality control limit their discriminating power and have led to a need for the development of instrumental techniques for the elemental analysis of glass fragments that provide better discrimination between specimens. This project addresses the optimization, standardization and validation of a method for the analysis of small glass samples (~ 2 mg) by ICP-MS using external calibration and isotope dilution experiments. Later on, we will also introduce laser ablation LA-ICP-MS for the analysis of glass using isotope ratios. The limitations of the instrumental techniques and the sample preparation protocols, including challenges in the dissolution of the glass or uniformity of the sample, are to be evaluated. A representative set of glasses (~1000) from a variety of sources will be analyzed by these methods to determine the informing power of elemental analysis determinations from glass specimens. I began in the Ph.D in Chemistry program in the Spring of 1999. In the summer of 1999 I was a graduate student guest at Oak Ridge National Laboratory, Chemical and Analytical Science Division, Analytical Spectroscopy Section. Inorganic Mass Spectrometry Group. I began my research in the Fall of 1999. Scientific Papers, Book Chapters And Other Publications
Conferences, Workshops and Presentations
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Constructing a database for Cannabis sativa L.
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Characterization of Inks and their Aging PropertiesBy: Louis Morris, Master of Science in Forensic Science (Awarded 2002)The purpose of this research was to study the potential of two analytical techniques in distinguishing individual ink samples. Lines from forty-one (22 black, 19 blue) different pens were written on three types of paper and chemically analyzed. Thin Layer Chromatography/Laser Induced Fluorescence (TLC/LIF) was used to characterize the organic properties of dyes, while Laser Ablation Inductively Coupled Mass Spectrometry (LA/ICP/MS) examined their trace metal composition. TLC/LIF could not discriminate twelve out of the forty-one inks using Rf values and band fluorescence. LA/ICP/MS could not discriminate sixteen out of the forty-one inks using count ratios and relative percentages of selected metals. Copper was the most abundant element in all forty-one inks, while lead and zinc were the best discriminators. Seven out of the twenty-two black, and six out of nineteen blue pens could not be discriminated using either method. I began the Master of Science in Forensic Science in the Spring of 2000 and attended a summer internship at the U.S. Secret Service Laboratory in Washington D.C. I began my research on inks in the Fall of 2000. |
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Forensic Evaluation Of Automotive LensesBy: Susan T. Gross, Master of Science in Forensic Science (Awarded 2001)Hit and run type accidents and other vehicle accidents often leave trace evidence behind. This trace evidence can include small pieces of paint, body fillers, plastic bumper bars, tire rubber and/or plastic lenses. Due to the lack of background information as to the diversity and physical and chemical properties of plastic lenses, the evidentiary value of this type of evidence is unknown. To generate the discrimination power of automotive lenses, this study proposes to analyze the lenses by five different instrumental techniques. These techniques will examine both the organic and inorganic composition of these plastic lenses. The five techniques that will be utilized are: Pyrolysis Gas Chromatography (PGC), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Scanning Electron Microscopy - Energy Dispersive X-ray (SEM-EDX), and Laser Ablation Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS). Three of these techniques (PGC, FTIR and SEM-EDX) were chosen for this project since they are commonly found in forensic science laboratories and they characterize materials based on both organic and inorganic content. Two additional instruments that will be utilized in this project, that may provide additional information, are Raman and LA-ICP-MS. The informing power of using each of the techniques by itself and the informing power of using the techniques in combination are being researched. Automotive lenses of known origin are being analyzed in triplicate by PGC, FTIR, SEM-EDX, Raman, and LA-ICP-MS. Various autobody shops and junk yards were contacted to obtain a representative cross-section of automotive lenses that would be expected to be found at a crime scene. Automotive lenses were obtained from a variety of vehicles of model years 1985 through 2000. Both American and Foreign cars were included in this diverse sample set. Quantitative data from all five instrumental techniques will be summarized and evaluated by the method of Smalldon and Brown for the determination and assessment of discrimination power. I began in the Master's of Forensic Science program in the Fall of 1999. I began my research in the Spring of 2000. My research will be presented at the American Academy of Forensic Sciences at the 2001 Meeting in Seattle, Washington , February 19 - 24. Scientific Papers, Book Chapters And Other Publications
Poster and Oral Presentations At Scientific Meetings
Awards:
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Identification and Characterization of Pyrolysis Products in Fire Debris AnalysisBy: Eric Stauffer, Master of Science in Forensic Science (Awarded 2001)The objective of my research is to identify and characterize pyrolysis products found in fire debris in order to distinguish these compounds from possible ignitable liquid residues (ILR). Pyrolysis products are released by burning substrate during a fire. These products produce a response in a gas chromatograph that can mask the pattern of petroleum distillates, during the analysis of fire debris in a suspected arson case. Different objects and materials commonly encountered in fire debris analysis have been burned under different conditions and their pyrolysis products have been studied. Common materials considered to be possible sources of pyrolysis products once burned, and found in residential buildings have been classified into four main levels of types of substrates. Level 1 includes materials fixed on the floor, walls and ceiling of a building. Level 2 includes all the furniture and other large items that can be found in a room. Smaller objects found inside or nearby the furniture constitute level 3 type substrates. Finally, level 4 items are categorized as components within larger objects but are present in small quantities and not part of the bulk material of the object for example, the dyes found in carpet fibers. The dyes themselves would classify as level 4 while the polymer material of the carpet would classify as level 1. Each level is then separated into sublevels according to the class of compounds of the materials and objects found in each level such as polymers from a carpet fiber, wood products from a furniture item, natural fibers from cloth materials, etc. This classification has been constructed in order to be able to group some target pyrolyzates by both object types and by material (chemical) composition, after burning. A first study of pyrolysis products has been conducted under controlled heating conditions with a Pyrolyzer-Gas Chromatograph-Mass Spectrometer (CDS AS-2500, HP 6890-HP 5973). By using a pyrolyzer it has been possible to obtain the set of pyrolysis products released by the substrates under specific temperature conditions. Generally, there are only three degradation mechanisms by which the pyrolysis process occurs. The first one is random scission, which is the production of free radicals along the backbone of the polymer. The second is the side group scission, where the backbone loses molecules or atoms attached to it. The final one is monomer reversion in which the polymer returns simply to its monomer. Hence, it has been possible to study these degradation mechanisms and to compare them to the pyrolyzates obtained during the analyses. Samples have been burned under different conditions and extracted in the same way that ILR are usually extracted from fire debris. Passive headspace extraction using activated charcoal strip and elution with carbon disulfide has been used in this study. Analyses of the resulting extract were conducted with both GC-FID (HP 5890) and GC-MS (Varian 3400cx and Varian 2000). Resulting chromatograms were compared to the ones obtained by Py-GC/MS in order to estimate the influence of the different burning conditions and the extraction procedure. Then, these have been compared to a collection of ILR standards in order to estimate their interference using peak pattern analysis. It is possible to construct a classification of the pyrolysis products with respect to the different levels of objects and substrate materials. In addition, it has been possible to estimate some parameters in the burning procedure and in the extraction procedure that influence the presence of pyrolysis products. Finally, It has been possible to show the interference of pyrolysis products with the recovery of ILR. Furthermore, a comparison of the relative detection limits of gasoline in the presence of pyrolysis products is presented. The effectiveness of using a GC-FID compared to a GC-MS or GC-MS-MS is also presented. These studies show the improved detection and identification of ILR in the presence of pyrolyzates when GC-MS or GC-MS-MS are used over just GC-FID alone. I began my Master of Science in Forensic Science degree program at FIU and joined the group in the Fall of 1999. Oral Presentations At Scientific Meetings
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