Browsing by Subject "solid phase microextraction"

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    Advances in Solid Phase Microextraction for the Analysis of Volatile Compounds in Explosives, Tire Treatments, and Entomological Specimens
    (2016-05) Kranz, William D.; Goodpaster, John V.; Manicke, Nick; Sardar, Rajesh; Picard, Christine Johanna; Long, Eric C.
    Solid phase micro-extraction is a powerful and versatile technique, well-suited to the analysis of numerous samples of forensic interest. The exceptional sensitivity of the SPME platform, combined with its adaptability to traditional GC-MS systems and its ability to extract samples with minimal work-up, make it appropriate to applications in forensic laboratories. In a series of research projects, solid phase micro-extraction was employed for the analysis of explosives, commercial tire treatments, and entomological specimens. In the first project, the volatile organic compounds emanating from two brands of pseudo-explosive training aids for use in detector dog imprinting were determined by SPME-GC-MS, and the efficacy of these training materials was tested in live canine trials. In the second project, the headspace above various plasticizers was analyzed comparative to that of Composition C-4 in order to draw conclusions about the odor compound, 2- ethyl-1-hexnaol, with an eye toward the design of future training aids. In the third, automobile tires which had participated in professional race events were analyzed for the presence of illicit tire treatments, and in the fourth, a novel SPME-GC-MS method was developed for the analysis of blowfly (Diptera) liquid extracts. In the fifth and final project, the new method was put to the task of performing a chemotaxonomic analysis on pupa specimens, seeking to chemically characterize them according to their age, generation, and species.
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    Detection of prohibited treatment products on racing tires using headspace solid phase microextraction (SPME) and gas chromatography/ mass spectrometry (GC/MS)
    (Royal Society of Chemistry, 2016-01) Kranz, William D.; Carroll, Clinton J.; Goodpaster, John V.; Department of Chemistry & Chemical Biology, School of Science
    A variety of commercial tire treatments are available that purport to help automobile tires better cling to the surface of a road or racetrack, raising concerns in the professional racing community that such products might be used to illicitly boost performance in competitive events. These tire treatments are reputed to cut lap times and improve handling and maneuverability. In some cases, the manufacturers even boast that their products are “undetectable” (i.e., impervious to the scrutiny of laboratory testing). In this study, a number of banned tire treatment products were evaluated principally by gas chromatography-mass spectrometry (GC-MS) using solid phase microextraction (SPME) as a pre-concentration technique. The chemicals off-gassed by each product were determined and grouped into two broad categories: ‘plasticizer-based’ tire treatment products and ‘hydrocarbon-based’ tire treatment products. This information was then applied to the analysis of genuine tire samples provided by the United States Auto Club (USAC), a professional racing association. Over the course of one year, 10 out of the 71 questioned samples tested positive for a prohibited treatment product. The manufacturers' claims regarding their products' invisibility to lab tests were largely proven to be unfounded: both the products themselves and the tires treated with them can be identified by a number of characteristic volatile compounds. These included known plasticizers such as pentanedioic acid diethyl ester, plasticizer-related compounds such as 2-ethyl-1-hexanol, and dearomatized distillates.
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    Development of Total Vaporization Solid Phase Microextraction and Its Application to Explosives and Automotive Racing
    (2015) Bors, Dana E.; Goodpaster, John V.; Picard, Christine Johanna; Shepson, Paul; Cooks, Graham; Long, Eric C.
    Pipe bombs are a common form of improvised explosive device, due in part to their ease of construction. Despite their simplistic nature, the lethality of pipe bombs should not be dismissed. Due to the risk of harm and their commonality, research into the pipe bomb deflagration process and subsequent chemical analysis is necessary. The laboratory examination of pipe bomb fragments begins with a visual examination. While this is presumptive in nature, hypotheses formed here can lead to subsequent confirmatory exams. The purpose of this study was to measure the mass and velocity of pipe bomb fragments using high speed video. These values were used to discern any trends in container type (PVC or black/galvanized steel), energetic filler (Pyrodex or double base smokeless powder), and ambient temperature (13°C and -8°C). The results show patterns based on container type, energetic filler, and temperature. The second stage of a laboratory exam is chemical analysis to identify any explosive that may be present. Legality calls for identification only, not quantitation. The purpose of this study is to quantitate the amount of explosive residue on post-blast pipe bomb fragments. By doing so, the instrumental sensitivities required for this type of analysis will be known. Additionally, a distribution of the residue will be mapped to provide insight into the deflagration process of a device. This project used a novel sampling technique called total vaporization solid phase microextraction. The method was optimized for nitroglycerin, the main energetic in double base smokeless powder. Detection limits are in the part per billion range. Results show that the concentration of residue is not uniform, and the highest concentration is located on the endcaps regardless of container type. Total vaporization solid phase microextraction was also applied to automotive racing samples of interest to the National Hot Rod Association. The purpose of this project is two-fold; safety of the race teams in the form of dragstrip adhesive consistency and monitoring in the form of fuel testing for illegal adulteration. A suite of analyses, including gas chromatography mass spectrometry, infrared spectroscopy, and evaporation rate, were developed for the testing of dragstrip adhesives. Gas chromatography mass spectrometry methods were developed for both nitromethane based fuel as well as racing gasolines. Analyses of fuel from post-race cars were able to detect evidence of adulteration. Not only was a novel technique developed and optimized, but it was successfully implemented in the analysis of two different analytes, explosive residue and racing gasoline. TV-SPME shows tremendous promise for the future in its ability to analyze a broad spectrum of analytes.
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    Mapping explosive residues on galvanized pipe bomb fragments using total vaporization solid phase microextraction (TV-SPME)
    (Royal Society of Chemistry, 2015-12) Bors, Dana; Goodpaster, John V.; Department of Chemistry and Chemical Biology, School of Science
    Solid phase microextraction (SPME) is a popular sampling technique whereby analytes are sorbed to a coated fiber and subsequently desorbed into an analytical instrument. In headspace SPME, analytes partition between the sample, the headspace above the sample, and the SPME fiber coating. In total vaporization SPME (TV-SPME), sample extracts are heated until both the solvent and analytes completely vaporize, whereupon the analytes partition between the vapor phase and the SPME fiber. In this study, TV-SPME using a polyethylene glycol fiber was coupled with fast gas chromatography/mass spectrometry to identify components of double-base smokeless powder (DBSP). Nitroglycerin (NG), diphenylamine (DPA) and ethyl centralite (EC) were separated in under 5 min. For NG, the optimal sample volume (70 μL), extraction temperature (60 °C) and extraction time (20 min) resulted in a method that was over twelve fold more sensitive than traditional liquid injection and with a detection limit below 1 ppb. This method was then used to quantify DBSP residue on post-blast debris from five galvanized steel pipe bombs. The mean concentration of NG on the fragments was 0.25 ppm (w/w). An average of 1.01 mg of NG was recovered from the devices. Finally, the distribution of NG could be “mapped” by tracking the original locations of each fragment within the device. These maps showed that the distribution of NG was far from uniform. In fact, the concentration of the NG on fragments originating from the end caps was several fold higher than in other locations. This finding can help guide the selection of bomb fragments for chemical analyses in real-world scenarios.
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    Optimization of total vaporization solid-phase microextraction (TV-SPME) for the determination of lipid profiles of Phormia regina, a forensically important blow fly species
    (Springer, 2017-11) Kranz, William; Carroll, Clinton; Dixon, Darren; Picard, Christine J.; Goodpaster, John V.; Chemistry and Chemical Biology, School of Science
    A new method has been developed for the determination of fatty acids, sterols, and other lipids which naturally occur within pupae of the blow fly Phormia regina. The method relies upon liquid extraction in non-polar solvent, followed by derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) w/ 1% trimethylchlorsilane (TMCS) carried out inside the sample vial. The analysis is facilitated by total vaporization solid-phase microextraction (TV-SPME), with gas chromatography-mass spectrometry (GC-MS) serving as the instrumentation for analysis. The TV-SPME delivery technique is approximately a factor of five more sensitive than traditional liquid injection, which may alleviate the need for rotary evaporation, reconstitution, collection of high performance liquid chromatography fractions, and many of the other pre-concentration steps that are commonplace in the current literature. Furthermore, the ability to derivatize the liquid extract in a single easy step while increasing sensitivity represents an improvement over current derivatization methods. The most common lipids identified in fly pupae were various saturated and unsaturated fatty acids ranging from lauric acid (12:0) to arachinoic acid (20:4), as well as cholesterol. The concentrations of myristic acid (14:0), palmitelaidic acid (16:2), and palmitoleic acid (16:1) were the most reliable indicators of the age of the pupae.