Browsing by Subject "Gas chromatography"

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Novel findings to aid in alcohol use disorder research : ethanol vapor and the ventral tegmental area
(2021-07-30) Ontiveros, Tiahna; Gonzales, Rueben Anthony
The high prevalence of alcohol use disorder continues to impact individuals by heightening stress, anxiety and disrupting cognitive tasks (Morrow and Creese, 1986). Ethanol affects several neuromodulator systems, exerting its effects within the central nervous system (Deehan et al., 2013). One known effect of ethanol is its impact on the mesocorticolimbic system and related circuits, including the ventral tegmental area and its involvement in the regulation of motivation and goal-directed behavior (Doyon et al., 2020). The neurotransmitter norepinephrine has also been linked to mood stabilization, alertness, as well as the endocrine and autonomic nervous systems (Vazey et al., 2018). Additional issues remain to be explored, such as the interaction between norepinephrine signaling and other neuromodulators, and a better mechanistic understanding of ethanol withdrawal (Kushner et al., 2000; Skelly and Weiner 2014; Fredriksson et al., 2015; Becker and Koob, 2016; Petrakis et al., 2016). In order to increase our understanding of alcohol use disorder I carried out two experiments throughout the course of my thesis. We conducted an ethanol vapor study showing that we were able to successfully induce alcohol dependence and withdrawal through a short ten-day vapor exposure model in Long Evans male rats. Lastly, we created a time course of ethanol in the ventral tegmental area through gas chromatography analysis, also using microdialysis. In the appendix we also show pilot data from a study were we closely examined the estrous cycle in female rats that underwent surgery to place an intracranial guide cannula for microdialysis experiments. We found the possible surgical effects that can halt cycling and ultimately affect data looking at differences between males and females in alcohol dependance and withdrawal, however more experiments are necessary to make a precise conclusion. Findings from these three experiments can be used to continue the advancement of alcohol use disorder research in different ways.
Oxidative degradation of piperazine in the absorption of carbon dioxide
(2005-05-21) Alawode, Akinleye Olaolu; Rochelle, Gary T.
Oxidative degradation of piperazine was quantified by using Gas and Ion Chromatography. The GC analysis involved the direct analysis of the piperazine using calibration standards, while the IC analysis was based on quantifying acetate, a degradation product which is an indication of piperazine loss. This study used an agitated reactor maintained at 55̊C, with conditions similar to those in absorber/stripper configurations for CO₂ removal from flue gas. The problems encountered with the apparatus by the previous investigator were eliminated and the effect of varying some process parameters such as catalyst concentration, duration and agitation on degradation was studied. The rate of acetate production ranged from 0.08 to 0.4mM/hr while actual piperazine loss ranged from 1mM/hr to 5mM/hr. The degradation rate was found to be dependent on agitation rate and catalyst concentration
Phthalates and polybrominated diphenyl ethers in retail stores
(2012-12) Urquidi, Jorge Rodolfo; Xu, Ying (Assistant professor); Siegel, Jeffrey
Retail stores are an environment with a rich diversity of toxic chemicals typically found in consumer products. Among these chemicals, semi-volatile organic compounds (SVOCs) are an important class with great health concerns. Phthalates and polybrominated diphenyl ethers (PBDEs) are high production volume SVOC chemicals pervasively used in plastics and other consumer products. Exposure to them may cause serious adverse health effects, including endocrine disruption. They, however, have not been widely studied in retail environments. In this study, indoor air samples were collected from 15 retail stores in Austin, TX and University Park, PA. Some of these stores were revisited on different temperate seasons to account for weather variability. Indoor concentrations of the most ubiquitous pollutants were correlated with several building characteristics, including retailer type, temperature, and building use characteristics. Collected data shows a wider variety of phthalates and PBDEs, as well as higher indoor airborne concentrations for large department stores as compared to grocery stores, which typically have fewer sources in comparison.
Transport and sorption of noble gases in porous geological media
(2017-05) Paul, Matthew John; Biegalski, Steven R.; Haas, Derek; Landsberger, Sheldon; Lowrey, Justin
The transport of noble gas radionuclides in porous media is critical to the detection of underground nuclear explosions as well as the sequestration of reprocessing off-gases. However, in field tests releasing radioxenon underground, the quantity of radioxenon observed at the surface has fallen well below expectations. This research has examined the diffusivity and sorption of noble gases (Ar, Kr, and Xe) and the inert molecular gas sulfur hexafluoride (SF₆) in both dry and wet porous media seeking a plausible mechanism for this discrepancy. In support of this, the two-bulb method for estimating diffusivity has been modified for experimentation in porous media. To replicate underground transport conditions, low-level concentrations of the tracer gas species were required. Detecting trace quantities of these inert species necessitated the development of precision gas chromatography-mass spectrometry (GC-MS) capabilities for these permanent gases. This was accomplished through the use of internal standards; atmospheric nitrogen, which contains the scarce isotope ¹⁵N, and synthetic carbon tetrafluoride, CF₄, were both utilized. Both internal standards were shown to be capable of producing acceptable results under ideal conditions, but the CF₄ method showed more resiliency. The results of the diffusivity trials demonstrated the adequacy of the porosity-tortuosity factor model for both dry and wet macroporous media. However, in both the dry and wet trials, the equilibrium concentration of Xe converged at a lower fraction of initial concentration than the other tracer gases considered. The deviation in equilibrium fraction is expected in the wet trial due to the increased solubility of Xe versus the other tracer species. However, deviation in the dry trial necessitates consideration of adsorption effects. While the physical adsorption of Xe on shale formations has been considered as a potential mechanism for the scarcity of primordial Xe isotopes in the atmosphere, adsorption measurements were conducted on a range of materials demonstrating not only the relative strength of xenon adsorption over other noble gases, but also that the magnitude of this effect readily exceeds that of solubility. Consequently, with the observation of significant gas adsorption, consideration of adsorbed phase accumulation is necessary when scaling to larger geological systems.