This study may be divided into two sections which cover different aspects of the reproducibility problems encountered in HPLC. In the first, the study has involved the separation of basic drugs, on different manufacturer's reversed-phase columns in conjunction with an acid buffered acetonitrile/water gradient. The retention reproducibility of each drug was assessed and compared on the basis of the retention index scale of 1-nitroalkanes. The effect of changing gradient run time on the reproducibility of the retention values of the 1-nitroalkanes was demonstrated on reversed-phases of different makers. The optimisation of initial isocratic composition of organic (acetonitrile) was carried out and its effect on the reproducibility of retention of basic drugs was evaluated. The effect of a premixed eluent on the retention reproducibility of selected basic drugs with time intervals between injections was demonstrated. The same method was further extended with or without using helium gas with small flow. The prediction of dwell volume and its effect on retention reproducibility was evaluated. Determination of retention times changes for selected aqueous basic solutes against eluent with different pH values on Capcell ODS column was studied. Applicability of each reversed-phases (Cl8) for the separation of basic analytes was demonstrated. In the second section, a number of different unbonded (bare) silicas were studied in terms of surface analysis using of solid state cross-polarisation (CP) magic angle spinning (MAS) NMR and Fourier Transform (FT) Diffuse Reflectance Infrared Spectra (DRIFT-IR) data. It is believed that silica material used for HPLC separation with eluent undergoes an ageing process with acidic (at pH:2–3) and basic eluents (higher than pH:8). To examine this process more clearly, some basic analytes were selected to evaluate each of the accelerated ageing process followed by showing the final surface properties by the method most commonly used such as solid-state NMR and FT-IR along with BET surface analyser.

<p> Electrokinetic chromatography is a variation of capillary electrophoresis that allows for the separation of nonionic analytes by selective interaction with an ionic pseudostationary phase dissolved in the background electrolyte. The utility of electrokinetic chromatography to characterize pseudostationary phases and pseudostationary phase&ndash;solute interactions has been recognized since its introduction. The objective of this dissertation was to use electrokinetic chromatography and copolymer stabilized lipid bilayer nanodiscs as a pseudostationary phase to characterize small molecule-lipid bilayer interactions. </p><p> Styrene-maleic acid copolymers were used to stabilize cylindrical sections of lipid bilayer in solution, forming nanodiscs. The nanodiscs are formed based on strong hydrophobic interactions between the styrene moiety, on the copolymer, and the alkyl tails of the lipids. Using the nanodisc pseudostationary phase, the affinity of the bilayer structure for probe solutes was characterized. Linear solvation energy relationship analysis was employed to characterize the changes in solvent environment of the nanodiscs of varied copolymer to lipid ratio, copolymer chemistry and molecular weight, and lipid composition. Increases in the lipid to copolymer ratio resulted in smaller, more cohesive nanodiscs with greater electrophoretic mobility. Nanodisc structures with copolymers of different chemistry and molecular weight were compared and showed changes in solvent characteristics and selectivity. Seven phospholipid and sphingomyelin nanodiscs of different lipid composition were characterized. Changes in lipid head group structure had a significant effect on bilayer?solute interactions. In most cases, changes in alkyl tail structure had no discernible effect on solvation environment. </p><p> The nanodisc pseudostationary phase was also used to study sphingomyelin stereochemistry. Various studies have produced conflicting results regarding whether interactions with lipid bilayers are or can be stereoselective. Using sphingomyelin nanodiscs stereoselective interactions between a pair of atropisomers, R-(+)/(S)-(&ndash;) 1,1'-Bi-2-naphthol, were demonstrated. </p><p> Finally the dissociation constants between sphingomyelin nanodiscs and solvochromatic analytes were measured and then validated using steady state fluorescence. Using nanodisc affinity capillary electrophoresis, dissociation constants were derived on the same order of magnitude as the dissociation constants derived using the fluorescent technique. Future directions of this project will be to study peptide and protein interactions with lipid bilayers of interest.</p><p>

<p> Current factories producing plant-based fossil-fuel replacements are neither environmentally friendly nor economically viable because their main product, bio-oil, is burned for heat rather than sold for profit. However, bio-oil is rich in potentially valuable aromatic compounds. In order to valorize bio-oil and improve the economic viability of the factories, we need to understand bio-oil&rsquo;s composition and the effect of processing parameters&mdash;such as plant feedstock and pretreatment method. Unfortunately, bio-oil is a complex lignocellulosic mixture that is difficult to analyze. To fully characterize the hundreds of compounds present, analysis typically requires top-end mass spectrometers and lengthy separations. This cost prohibits many laboratories from pursuing bio-oil research. Then time-consuming separations limit recursive analyses to optimize process parameters. The question takes shape: is it possible to analyze complex lignocellulosic mixtures without lengthy separations or top-end mass spectrometers? To assess the feasibility of rapid, affordable analysis, I set out to develop qualitative and quantitative methods using a quadrupole-time-of-flight (QTOF) mass spectrometer. I hypothesized that (a) ionization dopants could mitigate the need for lengthy separations pre-injection and that (b) tandem mass spectrometry could compensate for the midrange resolving power of the QTOF. To test this hypothesis, I started by analyzing another lignocellulosic biomaterial: autohydrolyzate, the product of hydrothermal pretreatment of biomass feedstocks. I observed that two anionic dopants&mdash;hydroxide and chloride&mdash;worked exceptionally well for selective analysis of the two major components of a lignocellulosic mixture, lignin- and carbohydrate-derivatives. Tandem mass spectrometry confirmed the game-changing selectivity of the dopants. With these favorable results, I applied the ionization dopants to two case studies. Chloride dopant and tandem mass spectrometry were employed to qualitatively analyze the little understood lignin-carbohydrate complexes found in lignocellulosic mixtures. Hydroxide dopant and tandem mass spectrometry were employed to quantitatively analyze the feasibility of valorizing biooil as a performance-enhancing diesel fuel additive. Both projects offered exciting success that redefined the scope of research possible using a QTOF. I demonstrated that by using ionization dopants and tandem mass spectrometry, it is possible for laboratories with limited means to use a cost-effective QTOF for both qualitative and quantitative analysis of complex lignocellulosic mixtures. </p><p>

One of the strongest construction materials in relation to its weight is carbon fiber composites. The use of carbon fiber composites has increased substantially, for example in the automotive industry. Carbon fiber composites can decompose to respirable fibers and particles at high temperatures. The respirable fibers and particles can reach down to the alveoli in the lungs and cause inflammations. Respirable fibers have a diameter less than 3 μ m, a length longer than 5 μ m and a ratio between length and diameter equal to or greater than 3. Mechanical machining of carbon fiber composites decomposes the carbon fibers to inhalable fiber fragments with the original fiber diameter retained. Respirable fibers and fiber fragments can also transport other hazardous compounds or cause irritations on the skin and in the eyes. The aim of this study was to study the degree of contamination on protective clothes exposed to combustion or mechanical machining of carbon fiber composites. This to increase the understanding of the degree of contamination. The studied protective clothes were fire clothing from the emergency services in Karlskrona, disposable overalls used by the aircraft crash site group in the Swedish Armed Forces and lab coats used by Exova Materials Technology AB when mechanically machining carbon fiber composites. The protective clothes were washed after contamination to study how the contamination decreases after being washed. The contamination on the protective clothes were analyzed with GC - MS, microscopy and SEM. The conclusions from this study is that contamination of particles and fibers in varying sizes as well as gases are observed on the protective clothes, for example N,N - dimethyl formarmide and 1H,1H,2H,2H - perfluorooctan - 1-ol . Respirable fibers and particles were observed on the protective clothes after the combustion of carbon fiber composites. Washing the fire clothing and the lab coats eliminated the contamination. The contamination on the disposable overalls decreased after washing them, but did not eliminate the contamination completely

<p> N-nitrosodimethylamine is a carcinogenic disinfection byproduct which can be reformed after wastewater treatment if appropriate conditions are present. In this study various NDMA formation precursors over a range of conditions have been studied to attempt to quantify this NDMA reformation potential. Efforts were made in this study to demonstrate the effect of time, pH, and multiple different precursor chemicals on the reformation process. Dimethylamine (DMA) has been demonstrated to be a precursor chemical, and was chosen as a standard for initial experiments. The concentration of this precursor was kept constant at 100 ppt (parts per trillion) and solutions at three different pH&rsquo;s were tested over a 24-hour time period to see if any significant NDMA formation occurred. The impacts of various treated wastewater constituent chemicals including H₂O₂, monochloramine, dimethylhydrazine, etc. were also performed in this study. Significant difficulties occurred for the analysis of these samples, with large background interferences occurring in the method of analysis. Based on the data obtained, it appears that the formation potential of NDMA with DMA as a precursor was found to be the most efficient compound at basic pH (pH 9) and very basic (pH 13). This is consistent with the last step in wastewater remediation, where quicklime is added to the water to regulate the pH and for protection of distribution system. In addition, preliminary experiments were conducted using Ranitidine as a NDMA reformation precursor.</p><p>

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O estudo sistemático da extratibilidade de cianato e ciano-complexos de trifenil-n-propil e trifenil-isopropil-fosfônio, proporcionou a possibilidade de se efetuar, com eficiência, separações bem como de elaborar prova de identificação e métodos de determinação de interesse analítico. Mediante o emprêgo de íons cianato e de trifenil-isopropil-fosfônio, pôde-se estabelecer condições que permitiram extrair, do meio aquoso, íons de cobalto com 99,3% de eficiência (coeficiente de extração), em metil-isopropil-cetôna. Conseguiu-se, dessa maneira, separar baixos teores de cobalto de grandes quantidades de níquel. Pôde-se, assim, elaborar prova para a identificação de cobalto até 0,25 &#181;g, com limite de diluição de l:2.000.000. A prova pode ser executada na presença de grande número de íons estranhos. O método quantitativo elaborado, além de possibilitar a separação dos ions Co(II) e Ni(II), permitiu determinar cobalto na faixa de concentração de 4 a 60 &#181;g/ml, diretamente no extrato orgânico, por via espetrofotométrica, em 630 m&#181;. Isolou-se um composto correspondente à fórmula (&#934;3-P-C3H7)2 [Co(OCN) 4] que se provou ser a espécie extraída no procedimento analítico. A marcante diferença de comportamento observada entre o ferrocianeto de trifenil-n-propil ou trifenil-isopropil-fosfônio e o correspondente ferricianeto, permitiu a elaboração de método para a separação quantitativa dêsses anions, mediante extração, em álcool pentílico, do ferricianeto -de trifenil-n-propilfosfônio, sendo o coeficiente de extração 97,5%. A medida espetrofotométrica, direta, do ferricianeto extraído, em 420 m&#181;, permite determinar 20 a 200 &#181;g/ml. Entretanto, após reação, na própria fase orgânica, com íons Fe(II), a coloração azul obtida tornou o método cêrca de oito vêzes mais sensível e aplicável na faixa de 2 a 18 &#181;g/ml, sendo a medida espetrofotométrica efetuada em 720 m&#181;. / O estudo sistemático da extratibilidade de cianato e ciano-complexos de trifenil-n-propil e trifenil-isopropil-fosfônio, proporcionou a possibilidade de se efetuar, com eficiência, separações bem como de elaborar prova de identificação e métodos de determinação de interesse analítico. Mediante o emprêgo de íons cianato e de trifenil-isopropil-fosfônio, pôde-se estabelecer condições que permitiram extrair, do meio aquoso, íons de cobalto com 99,3% de eficiência (coeficiente de extração), em metil-isopropil-cetôna. Conseguiu-se, dessa maneira, separar baixos teores de cobalto de grandes quantidades de níquel. Pôde-se, assim, elaborar prova para a identificação de cobalto até 0,25 &#181;g, com limite de diluição de l:2.000.000. A prova pode ser executada na presença de grande número de íons estranhos. O método quantitativo elaborado, além de possibilitar a separação dos ions Co(II) e Ni(II), permitiu determinar cobalto na faixa de concentração de 4 a 60 &#181;g/ml, diretamente no extrato orgânico, por via espetrofotométrica, em 630 m&#181;. Isolou-se um composto correspondente à fórmula (&#934;3-P-C3H7)2 [Co(OCN) 4] que se provou ser a espécie extraída no procedimento analítico. A marcante diferença de comportamento observada entre o ferrocianeto de trifenil-n-propil ou trifenil-isopropil-fosfônio e o correspondente ferricianeto, permitiu a elaboração de método para a separação quantitativa dêsses anions, mediante extração, em álcool pentílico, do ferricianeto -de trifenil-n-propilfosfônio, sendo o coeficiente de extração 97,5%. A medida espetrofotométrica, direta, do ferricianeto extraído, em 420 m&#181;, permite determinar 20 a 200 &#181;g/ml. Entretanto, após reação, na própria fase orgânica, com íons Fe(II), a coloração azul obtida tornou o método cêrca de oito vêzes mais sensível e aplicável na faixa de 2 a 18 &#181;g/ml, sendo a medida espetrofotométrica efetuada em 720 m&#181;.

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