The protic acid-catalyzed polymerization of 1,6-anhydro-6-D-glucopyranose (I) was first reported one-half century ago; however, the mechanism of this reaction has not been resolved and is the topic under investigation in this thesis. In an attempt to resolve this mechanism, a number of 1,6-anhydrides structurally related to 1,6-anhydro-B-D-glucopyranose (I) were prepared and polymerized. The C-2, C-3, or C-4 hydroxyl group was either specifically blocked, replaced by a hydrogen atom or positioned different sterically. The relative rates of disappearance of monomer in the polymerization reaction were measured and this information used to propose a reaction mechanism.

Thesis (Ph. D.)--Ohio University, March, 2001. / Title from PDF t.p.

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<p>Rare earth elements (REEs) are 15 elements in the lanthanide series plus scandium and yttrium. They are essential for clean energy, defense, and other high-tech industries. Production of high-purity REEs, however, is limited to a few countries, posing great supply risks. Separation of crude REE mixtures into individual REEs is the most challenging step because of similar physical and chemical properties of the REEs. Conventional REE purification processes are based on solvent extraction methods, which are inefficient, require thousands of separator units, and produce large amounts of waste. Chromatography methods are inherently more efficient than solvent extraction methods because of orders of magnitude higher interfacial area per unit volume. Low-cost chromatography sorbents, however, do not have sufficient selectivity for REE purification. </p><p>In this dissertation, ligand-assisted displacement (LAD) chromatography was developed for the separation and purification of REEs from complex mixtures. A ligand, which is selective for REEs, can be added in the mobile phase or immobilized in the sorbent to achieve REE separation and purification. Constant-pattern design methods and a general zone splitting strategy were developed for producing high-purity REEs with high yields and high productivities from complex mixtures. The new methods were tested for producing three high-value REEs, called the magnets REEs, which are the key ingredients in permanent magnets, neodymium (Nd), praseodymium (Pr), and dysprosium (Dy), from waste magnets, bastnäsite concentrates, and monazite concentrates. </p><p>A two-zone LAD was designed and tested for recovering high-purity <a>neodymium (Nd), praseodymium (Pr), and dysprosium (Dy) </a>from waste magnets. Three-zone LAD was designed to recover high purity Nd and Pr from bastnäsite and monazite concentrates. High purity REEs (>99.5%) were produced with high yields (>99%) and high productivities (>100 kg REEs/m³/day). </p><p>Compared to conventional solvent extraction methods, the LAD methods are inherently safer and greener, since they do not require flammable organic solvents or toxic extractants and generate much less waste. LAD methods require only a few zones with a small number of columns. They have more than 10 times higher productivity, or less than10 time the footprint, than solvent extraction. The LAD methods are also versatile and adaptable to a wide range of product purity requirement, feedstock composition, or production scale. </p><p>The LAD methods have the potential to transform the conventional solvent extraction methods with low efficiency and high environmental impact into more efficient and environmentally friendly chromatography methods. They can enable the production of the magnet REEs domestically and provide a driving force to change the current linear path of the REEs, from ores to permanent magnets, to landfills, into a more sustainable circular REE economy.</p>

Monoclonal antibodies are large, complex biomolecules that can be difficult to characterize. Characterization is important because of the various post translational modifications that can occur during manufacturing, processing, and storage. Some modifications can lead to efficacy and safety issues and therefore are heavily monitored. A leading way to monitor various modifications is by using liquid chromatography. The high sensitivity, reproducibility, and ability to quantitate analytes makes it very attractive for monoclonal antibody characterization. The large molecular size of monoclonal antibodies (150 kDa) makes them challenging to separate efficiently and with high enough resolution to be helpful. New column technologies that would help improve protein separation efficiencies and slectivities would greatly help in this challenging process. In this thesis, three novel bonded phases are developed for the separation of monoclonal antibodies including a weak anion and cation exchanger (WAX, CEX) for the separation of charged species as well as a novel hydrophilic interaction chromatography (HILIC) for the separation of glycoforms. Column develop is achieved by optimizing selectivity and improving efficiency of separations by altering particle surface chemistry.

Amongst the polar organic compounds occurring in unrefined and refined crude oils and the associated polluted production waters, complex mixtures of acids, known historically as naphthenic acids (NAs), have achieved prominence. This is particularly because NAs have been designated a toxicant class of concern in the oil sands process-affected water (OSPW) that has accumulated in vast quantities following exploitation of the oil sands of Northern Alberta, Canada in recent years. However, though there have been calls for NAs to be added to pollutant inventories, at the initiation of the current study, little knowledge existed of the exact composition of refined or unrefined NAs. The overall aim of the current study was therefore to identify individual NAs in refined (commercial) and unrefined (e.g. oil sands process-derived) complex mixtures of acids and then to assess the toxicity of any identified NAs. Individual NAs were tentatively identified by interpretation of the electron ionisation mass spectra of methyl ester derivatives, following comprehensive multidimensional gas chromatography-mass spectrometry (GCxGC-MS). Reference acids were then either purchased, or more commonly, where they were not commercially-available, synthesised, mainly by micro-hydrogenation methods, for co-chromatography and comparison of mass spectra of methyl esters with those of unknowns. The synthetic NAs, purified to >97% were then subjected to toxicological assessments using the Microtox™ assay. In all, 34 compounds were obtained pure enough for testing. Microtox results revealed that the toxicity endpoint (50% Inhibition Concentration, IC50) was between 0.004 and 0.7 mM. Exponential and other correlations were noted between carbon number and toxicity in several of the structural groups of acids assayed, which may be beneficial for predictions of toxicity of non-synthesised acids. Although n-hexanoic acid (IC50 0.7 mM) had the lowest toxicity, adamantane-type acids were the least toxic as a group overall. Conversely, the decahydronaphthalene (decalin)-type acids had the largest range of toxicities (IC50 0.004 to 0.3 mM) and the most toxic acid assayed was 3-decalin-1-yl-propanoic acid. According to USEPA guidelines many individual acids can be said to show low to medium toxicity. Since the acids in commercial and unrefined NAs occur in complex mixtures, an attempt was also made to assess mixture toxicity. Mixtures of individual structural groups of acids (e.g. acyclic isoprenoid acids, n-acids) and a mixture of all 34 acids were assessed. Apart from the adamantane sub-group of acids, all of the mixtures showed toxicities lower than the sum of the parts when calculated using equations for Concentration Addition and Model Deviation Ratios (simply the predicted IC50/Observed IC50). A hypothesis that achievement of a critical micelle concentration is required to produce toxicity was proposed to explain the lower than expected results. Some of the mass spectra of NA present in the commercial and unrefined mixtures were inconsistent with those of any of the alicyclic acids synthesised or purchased. These were hypothesised to be aromatic acids. Fractionation experiments of the NA mixtures using silver ion thin layer chromatography and solid phase extraction (Ag+TLC and Ag+SPE) were carried out in order to provide further evidence for aromatic acids. Ag+TLC allowed separation of a methylated NA mixture from OSPW into three distinct fractions; Ag+SPE resulted in eleven fractions, through the use of a wider range of solvents and differential solvent ratios. Analysis of the fractions by GC-MS revealed that each fraction was largely still made up of unresolved acids (as esters), although one or two fractions revealed some resolved acids. Use of averaged mass spectra and mass chromatography on each fraction revealed further resolved chromatographic peaks and associated interpretable mass spectra. Each of eight of the eleven sub-fractions were examined by GC-MS, in some cases by GCxGC-MS, and all by infrared spectroscopy, ultraviolet visible spectrophotometry and elemental analysis. A number of structures were proposed for the aromatic acids, including those with sulphur-containing moieties. It was noted that far from being minor components, aromatic acids comprised ca.25-40% of the OSPW acid extracts.

This diploma thesis will be focused on the identification and quantification of PAHs with molecular mass exceeding 278 Da by separation and spectrometric methods available at the laboratories of ICTEP.

In order to make gas chromatography (GC) more widely accessible, considerable effort has been made in developing miniaturized GC systems. Thermal gradient gas chromatograpy (TGGC), one of the heating methods used in GC, has recieved attention over the years due to it's ability to enhance analyte focusing. The present work seeks to develop high performance miniaturized GC systems by combining miniaturized GC technology with thermal gradient control methods, creating miniaturized thermal gradient gas chromatography (µTGGC) systems. To aid in this development a thermal control system was developed and shown to successfully control various µTGGC systems. DAQ functionality was also included which allowed for the recording of temperature and power data for use in modeling applications. Thermal models of the various µTGGC systems were developed and validated against the recorded experiemental data. Thermal models were also used to aid in decisions required for the development of new µTGGC system designs. The results from the thermal models were then used to calibrate and validate a stochastic GC transport model. This transport model was then used to evaluate the effect of thermal gradient shape on GC separation performance.

No description available.