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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Analytical applications of flow injection analysis.

Brown, Frank Reber. January 1987 (has links)
The rate of oxidation of copper metal to copper (I) by copper (II) in the presence of organic ligands has been determined for a variety of ligands using a flow injection analysis system to sample the reaction. The results obtained using the FIA sampling method compare favorably with those obtained in eariler work when allyl alcohol was used as the ligand. The mechanism proposed in that earlier work has been shown to be a general mechanism for the oxidation of copper metal in the presence of complexing ligands. It was found that some ligands increase the rate of the reaction beyond the ability of conventional FIA to sample many data points before the reaction reaches equilibrium. A method has been developed that allows for more rapid sampling of the reaction mixture by the FIA system, resulting in overlapping FIA peaks. These overlapping peaks can then be deconvolved by an iterative curve fitting/digital subtraction technique in which each peak in the FIA output is fitted to a model function and subtracted from the output, thus removing its effect on the peak height of subsequent peaks. The iodination of acetylacetone in acidic solution was also studied by the fast injection FIA technique. Iodine was generated coulometrically in the solution containing acetylacetone and hydrochloric acid. By this method, the keto-enol equilibrium constant of acetylacetone was determined over a range of pH's. They ranged from 2.3 x 10⁻⁵ at a pH of 2.63 to 1.8 x 10⁻⁴ at a pH of 4.03. It was also found that the reaction was first order with respect to the acetylacetone concentration.
2

The supramolecular chemistry of cucurbituril molecules

Lorenzo, Susan, Chemistry, Faculty of Science, UNSW January 2006 (has links)
The set of molecules cucurbit[n]uril (Qn) are macrocycles composed of n glycoluril monomers linked by methylene groups. These molecules have two oxygen-ringed portals of a diameter slightly smaller than their internal cavity diameter. This thesis describes syntheses, crystallisations, crystal structure determinations, crystal packing analyses and force field calculations exploring the supramolecular chemistry of Qn molecules and their derivatives. Qn acts as a host for guest molecules and at the outset of this project no metal containing molecule had been encapsulated in a Qn molecule. One aim of this project was to prepare such complexes. This was achieved with the synthesis and characterisation of crystalline {[cis-SnCl4(H2O)2]@Q7}2(SnCl6)3(H3O)6(H2O)23. Other compounds prepared and characterised crystallographically in the course of this project are: [(Q6)(Na3(H2O)8)]2[CoCl4]4[Co(H2O)6]2[CoCl(H2O)5]2(Cl)4, (Q5@Q10)(CH3COOH)(Cl)2(H3O)2(H2O)26, (Cl@Q5)4Q6(SnCl6)8(H3O)20(H2O)24, (Q8)3(PtCl6)4(H3O)8(H2O)x, (Q8)2(PtCl6)3(H3O)6(H2O)18, (Q7)(Cr3O10)(H3O)2(H2O)x and (Q6)(SnCl6)(H3O)2(H2O)x. While the smaller Qn (n = 5?) retain their circular forms, the larger Qn (n &gt 8) are less rigid and distort to accommodate larger guests. After analysis of the crystal structures of these Qn compounds and those listed in the Cambridge Structural Database, the principal packing motifs of the Qn molecules were elucidated. The most common is the portal-to-side interaction in which the portal oxygen atoms of one Qn approach the hydrogen atoms around the equator of another Qn. Force-field calculations on guest@Qn complexes were conducted to determine the mechanism for the formation of these complexes. A comparison of the intermolecular interactions of phenylated systems and comparable fluorinated phenyl systems was made using both crystal packing analyses and forcefield energy calculations. Intermolecular energy parameters for these calculations were derived and validated in this work. The principal fluorinated species studied was the [B(C6F5)4]?anion. Examination of its crystal structures found that the substitution of the hydrogen atoms by fluorine atoms is influential enough to alter the predominant intramolecular conformation. It is the ???flipper?conformer, between pairs of perfluorophenyl groups, that is overwhelmingly the favoured conformation and this has a strong effect on the types of phenyl embraces that a [B(C6F5)4]?anion will form. While the parallel 4PFE, the offset parallel 4PFE and the orthogonal 4PFE are all observed the 6PFE is not.
3

The supramolecular chemistry of cucurbituril molecules

Lorenzo, Susan, Chemistry, Faculty of Science, UNSW January 2006 (has links)
The set of molecules cucurbit[n]uril (Qn) are macrocycles composed of n glycoluril monomers linked by methylene groups. These molecules have two oxygen-ringed portals of a diameter slightly smaller than their internal cavity diameter. This thesis describes syntheses, crystallisations, crystal structure determinations, crystal packing analyses and force field calculations exploring the supramolecular chemistry of Qn molecules and their derivatives. Qn acts as a host for guest molecules and at the outset of this project no metal containing molecule had been encapsulated in a Qn molecule. One aim of this project was to prepare such complexes. This was achieved with the synthesis and characterisation of crystalline {[cis-SnCl4(H2O)2]@Q7}2(SnCl6)3(H3O)6(H2O)23. Other compounds prepared and characterised crystallographically in the course of this project are: [(Q6)(Na3(H2O)8)]2[CoCl4]4[Co(H2O)6]2[CoCl(H2O)5]2(Cl)4, (Q5@Q10)(CH3COOH)(Cl)2(H3O)2(H2O)26, (Cl@Q5)4Q6(SnCl6)8(H3O)20(H2O)24, (Q8)3(PtCl6)4(H3O)8(H2O)x, (Q8)2(PtCl6)3(H3O)6(H2O)18, (Q7)(Cr3O10)(H3O)2(H2O)x and (Q6)(SnCl6)(H3O)2(H2O)x. While the smaller Qn (n = 5?) retain their circular forms, the larger Qn (n &gt 8) are less rigid and distort to accommodate larger guests. After analysis of the crystal structures of these Qn compounds and those listed in the Cambridge Structural Database, the principal packing motifs of the Qn molecules were elucidated. The most common is the portal-to-side interaction in which the portal oxygen atoms of one Qn approach the hydrogen atoms around the equator of another Qn. Force-field calculations on guest@Qn complexes were conducted to determine the mechanism for the formation of these complexes. A comparison of the intermolecular interactions of phenylated systems and comparable fluorinated phenyl systems was made using both crystal packing analyses and forcefield energy calculations. Intermolecular energy parameters for these calculations were derived and validated in this work. The principal fluorinated species studied was the [B(C6F5)4]?anion. Examination of its crystal structures found that the substitution of the hydrogen atoms by fluorine atoms is influential enough to alter the predominant intramolecular conformation. It is the ???flipper?conformer, between pairs of perfluorophenyl groups, that is overwhelmingly the favoured conformation and this has a strong effect on the types of phenyl embraces that a [B(C6F5)4]?anion will form. While the parallel 4PFE, the offset parallel 4PFE and the orthogonal 4PFE are all observed the 6PFE is not.
4

Forensic sample analysis using supercritical fluid extraction coupled with solid phase microextraction

Lee, Emma-Jane January 2007 (has links)
A third of adults in the UK admit to using controlled substances at least once hi their lives and the most commonly abused drug was found to be cannabis, followed by the opiates and ecognine derivatives. Forensic laboratories are continually trying to reduce the turnaround time for samples submitted for analysis, to less than the current time of four days. One of the main aims of this work was to reduce the time taken to prepare, extract and analyse hair for target analytes. A new method combining supercritical fluid extraction and solid phase micro-extraction (SFE/SPME) is introduced. This coupled procedure utilises the advantages of using supercritical carbon dioxide as an extraction solvent and collecting the extract on a selected SPME fibre. Together the combined techniques provide a method that is solvent-free and highly selective, whilst reducing sample preparation to a minimum. Digested hair samples are examined by SEM to find the best method. Alkali hydrolysis and enzyme digestion using proteinase K were found to be the most effective pre-extraction methods. Solid hair samples with the addition of a derivatization reagent (BSTFA) gave the best results using the coupled technique. After optimisation and validation, the extraction from both real and spiked samples resulted in recoveries between 60% to 80% for the target analytes A9 -tetrahydrocannabinol (A9- THC) , cannabinol (CBN) and cannabidiol (CBD). Other forensic applications such as the extraction of polycyclic aromatic hydrocarbons and pesticides from environmental and food samples and the examination of fire debris for the presence of accelerants are also carried out. PAH could easily be extracted from complex matrices to give recoveries of up to 97% for some analytes at the optimized conditions of 90°C at 4500 psi over a 10 minute dynamic extraction period. Pesticide extraction gave recoveries of 60 - 80% while the extraction of accelerants from fire debris clearly showed that accelerants such as diesel can be identified over the coincidental PAH and hydrocarbon peaks found in burnt debris. The coupling of SFE to SPME provides an exciting technique that has a wide range of applications and creates potential for a fully automated on-line system.
5

Engineering amphiphilic fabrics for microfluidic applications

Owens, Tracie LeeAnne 14 November 2011 (has links)
Woven textile fabrics were designed and constructed from hydrophilic and hydrophobic spun yarns to give planar substrates containing amphiphilic microchannels with defined orientations and locations. Polypropylene fibers were spun to give hydrophobic yarns, and the hydrophilic yarns were spun from a poly(ethylene terephthalate) copolyester. Water wicking rates into the fabrics were measured by video microscopy and longitudinal wicking tests from single drops and from reservoirs. Intra-yarn microchannels in the hydrophilic polyester yarns were shown to selectively transport aqueous fluids, with the flow path governed by the placement of the hydrophilic yarns in the fabric. Simultaneous wicking of an aqueous and hydrocarbon fluid into the hydrophilic and hydrophobic microchannels of an amphiphilic fabric was successfully demonstrated. The high degree of interfacial contact and micron-scale diffusion lengths of such co-flowing immiscible fluid streams inside amphiphilic fabrics suggest potential applications as highly scalable and affordable microcontactors for industrial liquid-liquid extractions. The efficiency of liquid-liquid extractions carried out with the amphiphilic fabrics was evaluated. Solvent extraction efficiencies were shown to reach up to ~98%.
6

Identification of Tobacco-Related Compounds in Tobacco Products and Human Hair

Rainey, Christina 04 September 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Analyses of tobacco products and their usage are well-researched and have implications in analytical chemistry, forensic science, toxicology, and medicine. As such, analytical methods must be developed to extract compounds of interest from tobacco products and biological specimens in order to determine tobacco exposure. In 2009, R.J. Reynolds Tobacco Co. released a line of dissolvable tobacco products that are marketed as a smoking alternative. The dissolvables were extracted and prepared by ultrasonic extractions, derivatization, and headspace solid phase microextraction (SPME) with analysis by gas chromatography-mass spectrometry (GC-MS). The results show that the compounds present are nicotine, flavoring compounds, humectants and binders. Humectant concentrations vary among different tobacco types depending on the intended use. Humectants were quantified in various tobacco types by GC and “splitting” the column flow between a flame ionization detector (FID) and an MS using a microfluidic splitter in order to gain advantage from the MS’s selectivity. The results demonstrated excellent correlation between FID and MS and show that MS provides a higher level of selectivity and ensures peak purity. Chemometrics was also used to distinguish products by tobacco type. Hair is a common type of evidence in forensic investigations, and it is often subjected to mitochondrial DNA (mtDNA) analysis. Preliminary data was gathered on potential “lifestyle” markers for smoking status as well as any indications of subject age, gender, or race by investigating the organic “waste” produced during a mtDNA extraction procedure. The normally discarded organic fractions were analyzed by GC-MS and various lipids and fatty acids were detected. At this point, a total vaporization-SPME (TV-SPME) method was theorized, developed, and optimized for the specific determination of nicotine and its metabolite, cotinine. The theory of TV-SPME is to completely vaporize an organic extract which will eliminate the partitioning between the sample and the headspace, thereby simplifying the thermodynamic equilibrium. Parameters such as sample volume, incubation temperature, and extraction time were optimized to achieve the maximum analyte signal. Response surface methodology (RSM) is a statistical model that is very useful in predicting and determining optimum values for variables to ensure the ideal response. RSM was used to optimize the technique of TV-SPME for the analysis of nicotine and cotinine. Lastly, quantitation of nicotine and cotinine in human hair typically requires large sample sizes and extensive extraction procedures. Hence, a method using small sample sizes and a simple alkaline digestion followed by TV-SPME-GC-MS has been developed. Hair samples were collected from anonymous volunteers and nicotine and cotinine were identified and quantitated in the hair of tobacco users.
7

Development of Total Vaporization Solid Phase Microextraction and Its Application to Explosives and Automotive Racing

Bors, Dana E. January 2015 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / 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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