Browsing by Subject "TV-SPME"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Automated derivatization and identification of controlled substances via total vaporization solid phase microextraction (Tv-Spme) and gas chromatography-mass spectrometry (Gc-Ms)
    (2018) Hickey, Logan D.; Goodpaster, John
    Gas chromatography-mass spectrometry (GC-MS) is one of the most widely used instrumental techniques for chemical analyses in forensic science laboratories around the world due to its versatility and robustness. The most common type of chemical evidence submitted to forensic science laboratories is seized drug evidence, the analysis of which is largely dominated by GC-MS. Despite this, some drugs are difficult or impossible to analyze by GC-MS under normal circumstances. For these drugs, derivatization can be employed to make them more suitable for GC-MS. In Chapter 1, the derivatization of primary amino and zwitterionic drugs with three different derivatization agents, trifluoroacetic anhydride (TFAA); N,O-bis(trimethylsilyl)trifluoroacetamide + 1% trimethylchlorosilane (BSTFA + 1% TMCS); and dimethylformamide dimethylacetal (DMF-DMA), is discussed. The chromatographic performance was quantified for comparison between the derivatives and their parent drugs. Peak symmetry was compared using the asymmetry factor (As), separation efficiency was measured by the number of theoretical plates (N), and sensitivity was compared by measuring the peak areas. In Chapter 2, derivatization techniques were adapted for an automated on-fiber derivatization procedure using a technique called total vaporization solid phase microextraction (TV-SPME). TV-SPME is a variation of SPME in which a small volume of sample solution is used which can be totally vaporized, removing the need to consider the equilibrium between analytes in the solution and analytes in the headspace. By allowing derivatization agent to adsorb to the SPME fiber prior to introduction to the sample vial, the entire derivatization process can take place on the fiber or in the headspace surrounding it. The use of a robotic sampler made the derivatization procedure completely automated. In Chapter 3, this on-fiber derivatization technique was tested on standards of 14 controlled substances as well as on realistic samples including simulated “street meth”, gamma-hydroxybutyric acid (GHB) in mixed drinks, and hallucinogenic mushrooms, and was also tested on several controlled substances as solid powders. Future work in this area is discussed in Chapter 4, including adapting the method to toxicological analyses both in biological fluids and in hair. Some of the expected difficulties in doing so are discussed, including the endogenous nature of GHB in the human body. The presence of natural GHB in beverages is also discussed, which highlights the need for a quantitative addition to the method. Additional method improvements are also discussed, including proposed solutions for complete derivatization of more of the analytes, and for decreasing analysis time.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Factors Affecting Species Identifications of Blow Fly Pupae Based upon Chemical Profiles and Multivariate Statistics
    (MDPI, 2017-04-11) Kranz, William; Carroll, Clinton; Dixon, Darren A.; Goodpaster, John V.; Picard, Christine J.; Chemistry and Chemical Biology, School of Science
    Alternative methods for the identification of species of blow fly pupae have been developed over the years that consist of the analyses of chemical profiles. However, the effect of biotic and abiotic factors that could influence the predictive manner for the tests have not been evaluated. The lipids of blowfly pupae (Cochliomyia macellaria, Lucilia cuprina, Lucilia sericata, and Phormia regina) were extracted in pentane, derivatized, and analyzed by total-vaporization solid phase microextraction gas chromatography-mass spectrometry (TV-SPME GC-MS). Peak areas for 26 compounds were analyzed. Here we evaluated one biotic factor (colonization) on four species of blow flies to determine how well a model produced from lipid profiles of colonized flies predicted the species of flies of offspring of wild-caught flies and found very good species identification following 10 generations of inbreeding. When we evaluated four abiotic factors in our fly rearing protocols (temperature, humidity, pupation substrate, and diet), we found that the ability to assign the chemical profile to the correct species was greatly reduced.