This study was directed at developing a predictive kinetic model for ozone consumption by natural organic matter (NOM). The objectives of this research were: (1) to test an existing model, the Staehelin and Hoigne model, for aqueous ozone decomposition in a batch reactor, (2) to develop and test a model for determining the rate of change of aqueous ozone concentration during the ozonation of a simple organic model compound in a batch reactor, and (3) to develop and calibrate a kinetic model for determining the rate of loss of aqueous ozone and a hydroxyl radical probe compound during the ozonation of NOM in batch reactors. In the first stage of laboratory work, experiments were conducted to test the Staehelin and Hoigne model for aqueous ozone decomposition. Two of the rate constants of the Staehelin and Hoigne model were re-estimated in order to improve the agreement between the model predictions and the observed data at neutral pH and under several hydroxyl radical scavenger concentrations. In the second stage of laboratory work, batch ozonation experiments were conducted with the model compound, formic acid. The Staehelin and Hoigne model for ozone decomposition was incorporated in the model development. Natural organic matter, extracted from Forge Pond (Granby, MA) and separated into eight fractions, was ozonated in a batch reactor in the final stage of laboratory experiments. The Staehelin and Hoigne model was included in the model for ozone consumption by NOM. The concentrations of two types of ozone-consuming sites and associated rate constants were estimated for each fraction. The rate constants for all fractions were utilized in estimating average rate constants, which were then used to re-estimate the site concentrations of each fraction. These new estimates of site concentrations were employed in computing composite ozone-consuming-site concentrations for Forge Pond water. It was found that a two-parameter model was quite successful at describing both the residual ozone concentration profiles and the hydroxyl radical profiles (via the probe compound). This firmly established the framework for a central chemical kinetic model that can be used to predict the impact of ozone on micropollutants in waters containing NOM.

The introduction and presence of metals in the marine environment and their reaction and bioaccumulation in organisms and in the marine food web is of environmental importance. The identification and quantification of inorganic and organometallic compounds in marine samples is of importance in studies of the marine food chain and the accumulation of both nutrients and potentially toxic compounds in higher order marine organisms in the marine ecosystem. The goal of this doctoral research was to develop and apply analytical methodology to the sampling, isolation, speciation and determination of metals and organometallic compounds, notably those of the carbon-bonding main group elements such as mercury, tin and selenium in marine samples. The introduction of metals into the marine environment was investigated by analysis of phytoplankton samples cultured by the National Marine Fisheries Service. Procedures for extraction, fractionation and gas chromatographic determination by derivatization and element-specific detection by microwave plasma emission spectrometry (GC-AED) were developed. The biological pathways and transfer of elements along the food chain was investigated on a variety of marine samples including dogfish liver, mussel and lobster heptopancreas. This study was conducted in part at the National Institute of Standards and Technology (NIST), Gaithersburg, MD. Specifically this research centered around providing an alternative procedure to existing methodology for the determination of organomercury compounds in marine samples. Derivatization procedures developed in this research were exhaustively compared with direct gas chromatography of methylmercury chloride, as previously used by NIST. A modified version of the method developed for the analysis of phytoplankton samples allowed both inorganic and organomercury to be simultaneously measured at the μg/g level and below.

Molecular-beam mass spectrometry (MBMS) is a technique that is used to measure stable and radical species within flames, and thus it is a strong tool for understanding the formation and destruction pathways of precursors to PAH and soot. Using MBMS and modeling techniques, three well-chosen premixed flat flames have been characterized. Fuel-lean ethylene flames with and without added allene were mapped to help elucidate the C3H3 self-combination route to benzene formation, and a cyclohexane flame was characterized due to the abundance of cyclohexane within real fuels such as gasoline. Benzene is the precursor to PAH and soot whose formation is the rate-limiting step, and thus knowledge of its formation route is paramount. The flames characterized include an undoped fuel-lean (&phis; = 0.70), C2H4/O2/56.4% Ar flame (30.00±0.01 Torr and ub-300 = 30.6 cm/s), an allene-doped fuel-lean (&phis; = 0.69), 0.19 % C3H4/C2H 4/O2/56.54 % Ar flame (30.00±0.01 Torr and ub-300 = 30.6 cm/s), and a stoichiometric (&phis; = 1.00) cyclohexane/O2/32.5% Ar flame (30.00±0.01 Torr and ub-300 = 35.0 cm/s). Mole fraction profiles of 31, 35, and 70 stable and radical species were measured within the three flames, respectively. They are modeled with overall good agreement between the model and data. Comparison of both fuel-lean ethylene flames shows that benzene was detected in the allene-doped flame but not in the undoped ethylene flame, strongly suggesting the importance of C3 routes to benzene. Reaction path analysis showed that benzene in the allene-doped flame is mainly formed through propargyl self-combination as described by the kinetics of Miller and Klippenstein (2003). Examination of the cyclohexane flame showed high concentrations of benzene. A reaction path analysis showed that benzene is mainly formed instead by the dehydrogenation of cyclohexane. Experiments done at the Advanced Light Source of Lawrence Berkeley National Laboratory show that the isomeric C6H6 composition in the allene-doped flame consisted of 20% fulvene, 45% benzene and 35% 1,5-hexadiyne, while the cyclohexane flame consisted of 99.5% benzene and 0.5% fulvene. This difference in isomeric composition strongly points to the difference in benzene formation pathways in the two fuels.

Solvated transition metal solvent cluster ions were generated by electrospray ionization and their spectroscopy and photo dissociation dynamics have been studied by laser photofragment spectroscopy. Solvation of Co 2+ by water and methanol has been examined by studying Co2+ (H2O)n and Co2+(CH3OH) n (n = 4–7). An electrospray ionization reflectron time-of-flight mass spectrometer (ESI-RTOFMS) was developed to produce gas phase transition metal solvent cluster ions. This system couples with a Nd:YAG pumped dye laser to produce a unique mass spectrometry-laser photodissociation system. This instrument was compared to ESI-mass spectrometers in the literature. It shows a mass resolution (m/Δm) of 250 and a detection limit of 480 pmol. The instrument compares favorably to existing analytical instrumentation and several improvements are suggested. Hydrated cluster ions, Co2+(H2O)n (with n = 4–7), have been generated by electrospray ionization and studied by laser photofragment spectroscopy. The similarity between the spectrum of gas-phase Co2+(H2O)6 and the absorption spectrum of aqueous cobalt (II) suggests that Co2+(H2 O)6 (aq) is responsible for the room-temperature solution absorption spectrum. The observed photodissociation spectrum of Co 2+(H2O)4 is similar to new bands that appear in aqueous cobalt(II) at high temperatures and have been assigned to Co 2+(H2O)4 (aq) in the literature. The hexahydrate dissociates by loss of one or two water molecules, whereas the heptahydrate dissociates by loss of two or three water molecules. In both cases, loss of two water molecules is the preferred dissociation pathway. The tetrahydrate dissociates either by simple loss of water or by charge separation to form CoOH+(H2O)2 and H3O +, with charge separation being the preferred dissociation channel. Methanolic cluster ions, Co2+(CH3OH)n (with n = 4–7), show behavior similar to that of the hydrated clusters. The gas phase spectra display similar shifts from the solution absorption spectra, but absorb more strongly than the corresponding hydrated clusters. The hexamethanol cluster dissociates via loss of one or two methanol molecules; the heptamethanol cluster dissociates via loss of one, two or three methanols. The tetramethanol cluster primarily dissociates by a charge separation mechanism similar to that observed in the hydrated clusters, forming Co(OCH3) +(CH3OH)2 and H+(CH3OH); dissociation by simple loss of methanol is a minor channel.

The formation of specific phase-separated morphologies is central to achieving high performance polyurethanes. Polyurethanes are composed of various structural elements possessing a mixture of different functional groups, molecular weights, and sequence lengths. The chemistry, the phase behavior, and the kinetics of phase evolution will influence the type of phase-separated morphology formed. In fact, the phase behavior also depends upon the chemical structure and the molecular weight distribution of the components. Despite the importance of chemical structure, it is still not understood quantitatively. In addition, little is known about how the developing structure organizes into different phase-separated morphologies. The work herein addresses these issues. The molecular weight distributions, end groups, and linkages of polyurethane structural elements were quantitatively determined. The structural elements included polyether and polyester macrodiols, polyurethane prepolymers, and polyurea hard segments. Under homogeneous conditions, the molecular weight distribution formed obeys a Schultz-Flory distribution; although when toluene diisocyanates are used as the diisocyanate the effect of change in reactivity narrows the distribution. Under heterogeneous conditions, the phase separation of water causes a change in the local stoichiometry and narrows the distribution further. In the presence of typical polyurethane side reactions, the distribution is broadened. The formation of allophanate linkages was most prevalent in PPG prepolymers prepared at reaction temperatures of 145°C. Infrared spectroscopy was used to study the crystallization behavior of semicrystalline polyurethanes and the reaction and morphological evolution of polyurethane foams. Hydrogen bonding between urethane groups was shown to influence all aspects of the crystallization behavior, including the initial state, nucleation and growth rates, and the final morphology. Hydrogen bonding proves to be less crucial in the onset of phase separation in polyurethane foams. The most crucial parameter was shown to be hard segment anisotropy. Foams prepared from diisocyanates yielding highly anisotropic hard segments phase separate at lower reaction conversion, with a faster rate, and to a higher degree of phase separation and perfection.

Transferrins constitute a class of metalloproteins that sequester and transport iron in vertebrates. Understanding the metal-binding properties of transferrin is essential for studies of iron metabolism and metabolic disorders. However, dynamics of these systems is poorly understood, since they are not amendable to analysis by NMR due to the high spin of the metal ion and the large molecular weight of the protein (35–80 kDa). In this work we successfully developed and utilized an ESI MS based approach to study metal-release properties of the human serum transferrin N-lobe (hTF/2N), as well as the intact transferrin from human (hTF). Both composition and conformation of a protein complex was monitored under a variety of conditions that are designed to mimic extracellular and endosomal environments. It was determined that iron dissociation occurs in vitro at typical endosomal pH 5.5 when physiological chelators (e.g. citrate) are present at endogenous levels. In the absence of such chelating agents, detectable iron release occurs at much lower pH (<4.5) and is accompanied by unfolding of the protein. ESI MS data also indicated the transient nature of the anion in the holo-protein. Furthermore, studies of hTF revealed that the conformation of the iron-free N-lobe is stabilized when the C-lobe contains iron, confirming the existence of an interlobe interaction within the protein. Another surprising discovery was that the apo-N-lobe is significantly less flexible compared to the apo-C-lobe. These results provide strong support for the earlier suggestions that hTF interacts with its receptor (TfR) primarily through the C-lobe both at the cell surface and inside the endosome. We also successfully extended the above ESI MS approach to characterize interaction of intact transferrin (80kDa) with metals of medicinal relevance, such as In3+ and Bi3+. The results of our studies have revealed that indium-hTF complex exhibits the same pattern of conformational and metal release properties as iron-hTF. Because of conformational similarities between indium-hTF and iron-hTF, it is possible that indium-hTF is recognized by transferrin receptor protein (TfR) at the cell surface and is transported into the cells by the same mechanism of receptor mediated endocytosis as iron. On the other hand the results of our bismuth studies suggest that hTF adopts a semi-open conformation upon bismuth uptake. This conformation is different from that of iron-hTF, therefore it is likely that bismuth transport does not occur via the similar mechanism.

The study of hydride generation as an analytical technique has occupied a section of analytical chemistry for a considerable period of time. Applications of the technique have built upon the existing background of chemistry with few forward steps. The progress of analytical chemistry requires that the fundamental chemistry be studied so that it may then be applied within the understood limitations. Hydride generation is a technique that is heavily influenced by a variety of factors including but not limited to pH and oxidation state. The required oxidation state for hydride generation of arsenic and antimony is +3 and depending upon sample preparation, adjustment of the oxidation state is required. Bromide has been identified as a reductant for pentavalent arsenic and antimony and can be applied to reduce selenium to the hydride forming state of Se IV. Experiments are then described that demonstrate the limitations and application of bromide as a reductant for the simultaneous reduction of arsenic, antimony and selenium to the optimum hydride forming state, prior to hydride generation. The post-column chemistry of arsenic is examined with the application of microwave-assisted chemistry to the digestion of organoarsenical species. A mixture of bromide and bromine is applied under conditions that are also successful for the post column digestion of organoselenium compounds. The significance of the post column digestion is that it will assist in the development of simultaneous determination of arsenic and selenium species. The post-column chemistry of antimony has thus far been limited to the addition of borohydride under conditions that compromise the sensitivity of the species studied and is limited to those species that are borohydride active. There are several reports in the literature of unidentified antimony species that were not identified by the technique of hydride generation. Therefore, the application of photo-oxidation to those species would enable their subsequent determination by hydride generation. Two small projects with graphite furnace atomic absorption spectrometry are also discussed. The first project describes the development of a method for the determination of gold in cell structures. The second describes the measurement of bismuth in transferrin protein.

The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW™ based code (LabVIEW™ 7.1) in real time. The SALS apparatus was custom built for ExxonMobil Research in Clinton NJ.

Arsenic contamination of the environment is a worldwide health hazard. This research project focused on four areas: development and testing of low cost, field portable devices capable of measuring levels of arsenic at 10 μg L-1 or less; specific chemical techniques for such testing; creation of educational tools and techniques to allow operators who lack advanced chemistry training to perform accurate testing; and the determination and use of a biomarker in DNA as a cancer predictor in individuals exposed to environmental arsenic. The analytical techniques explored include: (1) the Gutzeit method of arsenic determination though arsine gas production, which was investigated in three experiments: measuring arsenic levels in soil samples, using Gutzeit-based kits using silver nitrate as a reactant for arsine gas, and sensitivity comparison of three commercial test kits over varying time periods up to twenty-four hours. (2) The molybdenum blue method, technologically quantified through three different experiments: digital photographic analysis, spectroscopic analysis, and flow injection. (3) Filtration of arsenic contaminated water with wood-ash, sand, ferric oxide, and commercially available steel wool; and the construction of a filtering device constructed of recyclable discarded soda bottles. Further, single nucleotide polymorphisms in the DNA of arsenic exposed individuals were studied to determine what immune response genes might be implicated in arsenic susceptibility. The major conclusions of this research were: digital image analysis used with the Gutzeit method improves precision and accuracy; silver nitrate proved to be a better measurement tool at low concentrations of arsenic than mercuric bromide; and the Gutzeit method can be applied to soils in the Hach kit.

The initial steps involved in the assembly of normally soluble proteins into amyloid fibrils remain unclear, yet over 20 human diseases are associated with proteins that aggregate in this manner. Protein surface modification is a potential means of mapping the interaction sites in early oligomers that precede amyloid formation. This dissertation focuses on the use of covalent labeling combined with mass spectrometry to elucidate the structural features of Cu(II)-induced β-2-microglobulin (β2m) amyloid formation. An improved covalent modification and MS-based approach for protein surface mapping has been developed to address the need for a reliable approach that ensures protein structural integrity during labeling experiments and provides readily detectable modifications. This approach involves measuring the kinetics of the modification reactions and allows any local perturbations caused by the covalent label to be readily identified and avoided. This MS-based method has been used to study human β2m, a monomeric protein that has been shown to aggregate into amyloid fibrils in dialysis patients leading to dialysis-related amyloidosis. Under conditions that lead to β2m amyloid formation, reactions of β2m with three complementary covalent labels have been used to identify the Cu(II) binding site, metal-induced conformational changes, and the oligomeric interfaces. Results confirm that Cu(II) binds to His31 and the N-terminal amine. Binding to these residues causes several structural changes in the N-terminal region and ABED β-sheet which likely enables formation of oligomeric intermediates. The covalent labeling data indicate that the pre-amyloid β2m dimer has an interface that involves the antiparallel arrangement of ABED sheets from two monomers. Moreover, our covalent labeling data allowed us to develop a model for the tetramer in which the interface is mediated by interactions between D strands of one dimer unit and the G strands of another dimer unit. Lastly, the selective covalent modification approach has been used to delineate the structural changes in β2m after interaction with Cu(II), Ni(II), and Zn(II) and their effect on its aggregation. Our covalent labeling data indicates that the unique effect of Cu(II) appears to be caused by the site at which the metal binds the protein and the conformational changes it induces.