Electrically-driven separation schemes, such as zone electrophoresis (ZE), isotachophoresis (ITP) and isoelectric focusing (IEF), are used profoundly to fractionate mixtures of charged compounds for preparative and particularly analytical applications. Inherent to the separation process is the development of local variations in the electrical conductivity, pH, electric field, etc. One-dimensional, quantitative descriptions of the spatio-temporal evolution of these variations, and their role in the separation process, have been developed over the past two decades. These descriptions lend significant insight into the electromigrational behavior of analytes and buffer components. Nevertheless, because they are one-dimensional, such descriptions omit important effects of electrokinetic fluid motion. The fluid motion arises naturally in the context of the separation scheme, and affects the evolving spatial gradients associated with the separation process. One-dimensional simulations have also been plagued by numerical limitations associated with advection-dominant transport in regions of sharp concentration gradients. In this dissertation, the numerical difficulties are resolved, and a general two-dimensional model of electrokinetic separations is presented. Because the balance laws account for coupling of the velocity field to the ion transport, a variety of processes important to both microfluidic manipulations and analytical separations can be considered. High-ionic strength electroosmotic pumping and field-amplified sample stacking are examined in detail. It is demonstrated that unsteady fluid eddies disperse the gradients in the field variables, and this limits the efficacy of microanalysis processes. Scaling arguments suggest that, at least for simple geometries, approximate solutions to the general model are possible. Semi-analytic approximations are constructed for the fluid velocity v and electric field E, and the parameter space over which they apply is defined. These approximations reduce simulation times by about two thirds, and provide general information on the dominant physics in microanalysis processes. The scale analysis and simulation results demonstrate that although cross-sectional conductivity gradients meet or exceed those in the axial direction, the electric field is essentially unidirectional. Also, at sufficiently high electric field strengths (ca. several hundred V/cm), nonlinear electrohydrodynamic stresses begin to influence the fluid motion. Finally, if the electrical stresses are negligible, the semi-analytic solutions for v and E permit 1-D macrotransport representations of the solute transport. Effective 1-D simulations yield cross-sectionally averaged values for the field variables in orders of magnitude less simulation time than 2-D simulations.

The topic of this thesis is investigation of models applied to different aspects of separations and colloid science. Many tools are used for solving the models, which are manifested as boundary value problems. The problems are to determine the equilibrium electrostatics of a fluid droplet, the electrokinetics of such, the (nonuniform) temperature profile of an electrophoresis capillary due to Joule heating, and the temperature at the wall of the capillary. In the fluid drop model, special attention given to a drop that, in addition to the surrounding fluid, supports electrolytes. Matched asymptotic expansions based on thin double layers are applied to the equilibrium electrostatics problem. Attention is given to how conditions on the interface of the drop, such as discontinuity of equilibrium potential and the presence of surface excesses of solutes, affect the electrokinetics. A perturbation scheme is used to formulate a problem for the electrophoretic mobility of a droplet. An approximate solution for the mobility of a drop is derived, based on small interfacial potentials. The formula encompasses those of several past theoretical studies. A regular perturbation is used to determine heating effects in capillary electrophoresis, based on a small power input to the system. The resulting expression for temperature in the capillary is then used implicitly to determine the temperature at the wall of the capillary. Some of the results are compared with experimental data. For the drop electrophoresis problem, the electrophoretic mobility formula is compared with measured mobility of oil drops and drops in aqueous two-phase systems. In the study of heating in capillary electrophoresis, the implicit expression is used to make reasonable estimates of the wall temperature based on published operating conditions. Accuracy of all analytic estimates of the problems are tested against numerical solutions, taken to be exact. In all cases, the analytic approximations are satisfactorily accurate under appropriate conditions.

Raman spectroscopy has recently become a common laboratory analytical technique due to the introduction of technology such as lasers, charge-coupled devices, and holographic filters. The information given by Raman spectroscopy is complimentary to infrared absorption spectroscopy, but sample preparation is often much easier, if any is needed at all. Because of this, the field of Raman spectroscopy has expanded in many areas, including mineralogy. The ongoing development of a database of Raman spectra of minerals enables facile identification of many minerals. Pyroxenes are a class of minerals that make up approximately 25% of the Earth's upper mantle, to a depth of 400 km. A recently discovered phase change in pyroxenes, accompanied by a volume change, is now accepted as the origin of some deep-focus earthquakes, which are clustered at a depth of approximately 225 km. However, the bonding change that accompanies this phase change is not completely understood. Raman spectroscopy was utilized to follow the phase change of spodumene. Polarized spectra of an oriented single crystal of spodumene were utilized to assign Raman modes that were previously ambiguously assigned in the pyroxenes. The pressure-induced phase transition was also followed in LiFeSi2O6 utilizing both Raman spectroscopy and single crystal x-ray diffraction. Similarities were noted between the Raman spectra of spodumene and LiFeSi2O6, enabling the assignment of Raman bands in the second material studied. Finally, a third pyroxene, LiCrSi2O6, was studied with Raman spectroscopy while the sample was subjected to pressure. This material changed color with application of pressure and the color change was quantified with visible absorption spectroscopy. Though no phase change occurred in this material, changes in the spectra did occur at high pressures. These high-pressure changes in the Raman spectra were observed in all three crystals studied and could provide a better understanding of the pyroxenes at high pressures. Additionally, none of the three pyroxenes in P21/c phase displayed a doublet of peaks in the spectroscopic region that had been previously utilized as a benchmark for the identification of the P21/c phase of the pyroxenes until higher pressures. Spodumene did not display a doublet at any pressure studied.

Imaging spectroscopy combines the spatial discrimination of imaging techniques with the chemical information of spectroscopy to form a powerful tool for the study of chemically heterogeneous systems. This work describes the in situ qualitative and quantitative analysis of contaminant transport flow cells and of high-performance thin-layer chromatography (HPTLC) plates by near-infrared imaging spectroscopy. A solid-state, near-infrared imaging spectrometer was constructed for these studies. The spectrometer utilized an imaging quality acousto-optic tunable filter for wavelength selection over the 1.3-2.3 μ range and a cryogenically cooled, 240 x 324 pixel platinum silicide camera for detection. Samples were analyzed by either diffuse reflectance or diffuse transmittance using a 250 W quartz-tungsten-halogen lamp for sample illumination. The first series of investigations focused on the analysis of laboratory-scale flow cells, which are used to study the transport of non-aqueous phase liquid (NAPL) contaminants in the soil and groundwater. Current detection systems used for determining NAPL distribution are incapable of distinguishing between chemical components in NAPL mixtures, limiting flow cell experiments to the study of simple systems. This research utilized the near-infrared imaging spectrometer and multivariate calibration techniques to quantitatively determine the concentrations of individual constituents in binary NAPL mixtures within vadose zone and aquifer models. The vadose zone calibration data was used to determine the spatial distribution of each NAPL constituent in situ during a dynamic, multi-component flow cell experiment that modeled the remediation of NAPL contaminated soil. This technique, the first to quantitatively determine the in situ distribution of the individual NAPL phase constituents, represents the state of the art in detection for contaminant transport flow cells. The second series of investigations focused on analysis of samples on HPTLC plates. Conventional systems require visualization techniques to detect compounds lacking a chromophore or fluorophore. This research utilized the near-infrared imaging spectrometer as a non-destructive detection technique to provide qualitative and quantitative information for caffeine samples on HPTLC plates. Both diffuse reflectance and diffuse transmittance measurements provided detection limits of several micrograms. The caffeine spectrum was clearly distinguishable down to 25 μg using a diffuse reflectance geometry with a mirrored backing applied to the HPTLC plate.

A broadband, multichannel, single mode, planar waveguide based ATR spectrometer was developed. A sensitivity enhancement of three orders of magnitude compared to the conventional transmission spectroscopic technique has been experimentally achieved. Applications to protein submonolayers adsorbed on glass surfaces provided the first results on the spectral characterization of those molecular films. The increased information content and the higher sensitivity response allowed us to experimentally determine the molecular orientation of organic films over a broad spectral range. The work developed here is a research tool that allows the investigation of some fundamental problems of molecular assemblies and a platform to develop new technological devices of high sensitivity and selectivity, such as biosensors.

This work describes the construction of an inductively-coupled plasma tandem quadrupole mass spectrometer where a quadrupole ion storage trap acts as a second sector and collision cell to achieve neutralization or collisional dissociation of interfering species before mass analysis. Because most elements exist as singly-charged ions in an inductively-coupled plasma (ICP) plume, the ICP can be used as an ionization source for mass analysis (ICP/MS). By reducing the sample to elemental ions before mass analysis, ICP/MS spectra tend to be simple compared with those obtained by ICP-optical emission spectrometry (ICP-OES) where elements may have hundreds to thousands of emission lines and spectral overlaps can be severe. This is especially troublesome in the analysis of rare earth elements which have the largest numbers of active emission lines when excited in an ICP. In addition, detection limits by ICP/MS are often up to 3 orders of magnitude lower than by ICP-OES. ICP/MS analysis is not immune from isobaric and isotopic interferences or matrix effects. For most analyses, an acid digestion precedes aspiration as an aqueous solution into an argon plasma gas. This can lead to large amounts of Ar+ etc., which may interfere to varying degrees with analytes of interest. Oxides, argides and hydrides of matrix ions or other analytes may also form and interfere. These same processes can also split peak areas between the atomic form of an analyte and the molecular. In isotope ratio studies where precise measurements on more than one isotope per analyte are needed, these effects may be compounded. Isobaric interferences normally require high resolution mass analysis to resolve if they cannot be separated prior to sample introduction. However, the interface between a high vacuum, high resolution sector or ion cyclotron resonance mass spectrometer and an atmospheric pressure plasma is non-trivial and such instruments are expensive. The focus of this work is new approach which uses a collision cell where weakly-bound molecular species can be dissociated and ions with relatively high electron affinities, such as Ar+, can be neutralized through charge exchange reactions.

Organochlorine compounds, such as polychlorinated biphenyls (PCBs), pentachlorophenol (PCP), p,p'-DDE and Toxaphene, have been widely used in industry and agriculture for more than fifty years. Although they have served their purpose very effectively and at low cost, many of these compounds have been banned in the United States due to their persistence in the environment and their threat to human health. Their natural resistance to degradation has made organochlorine compounds the target of many studies that have been designed to convert them into less toxic compounds. At present there is not a single, simple method than can completely dechlorinate PCBs, PCP, p,p'-DDE and Toxaphene. The work presented here reports the use of a novel bimetallic system, palladized iron (Pd/Fe), to effect the complete dechlorination of these compounds, at ambient temperature and pressure, in a matter of minutes. The dechlorination reaction occurs on the surface of the palladized iron, with removal of all the chlorine atoms from the chlorinated compound and yields the completely dechlorinated molecule and chloride ions as reaction products. The chlorinated compound is reductively dechlorinated while the iron particles are oxidized to Fe²⁺ Water is also reduced in the presence of iron, generating hydrogen, which is collected in the palladium lattice. The palladium is therefore necessary to store hydrogen gas; the "Pd·H₂" acts as a powerful reducing agent and is primarily responsible for the rapid and complete dechlorination of the organochlorine compounds. The Pd/Fe bimetallic system is potentially useful for the large scale remediation of groundwater or soil contaminated with organochlorine compounds. Palladized iron is relatively inexpensive and easy to prepare, and it rapidly and completely dechlorinates organochlorine compounds. For these reasons, the Pd/Fe system should be investigated further for applications in the field.

Understanding and controlling protein adsorption is fundamentally important to the successful development of synthetic biomaterials and implantable chemical sensing devices. However, the study of protein adsorption, and in particular, orientation in protein thin films has been hampered by inadequate methods with which to study weakly absorbing thin protein films. In this work, Integrated Optical Waveguide-Attenuated Total Reflection Linear Dichroism (IOW-ATR LD) coupled with fluorescence emission anisotropy was used to study: (1) the orientation of Mb as a function of the adsorbent surface and surface coverage, and (2) the orientation distributions of cyt c adsorbed to various surfaces. It was found that the average molecular orientation of an adsorbed protein film: (1) is dependent on the chemical and/or physical characteristics of the adsorbent surface, and (2) is dependent on the protein surface coverage. It was also determined that the macroscopic order of an adsorbed protein film is dependent on the number of different types of protein-surface interactions in a given system. If there is one dominant type of interaction between the between the protein and the surface which is limited to a specific region on the surface of the protein, an ordered protein film will be produced. However, as the number of the type of protein-surface interactions increases, the distribution of orientations also increases, leading to a disordered film. Finally, a broadband waveguide coupling device has been developed which allows spectroscopic measurements of submonolayer to monolayer surface coverages of proteins to be performed.

New biomaterials for permanent cardiac pacemaking electrode applications based on Au surfaces chemically modified with self-assembled monolayers (SAMs) have been developed. The research described herein focuses on four areas related to understanding the extraordinary pacing exhibited by modified pacemaker electrodes. SAM-modified pacemaker electrodes were fabricated and tested in canines for chronic and acute cardiac pacing. In addition to having electrical properties suitable for pacing the heart, SAM-modified electrodes are proven superior to control electrodes in pacing performance. The data suggest that the biocompatibility of electrically conductive materials can be controlled at the molecular level with monolayer organic surface films. The development of a small rodent model for studying cardiac pacing was explored as an alternative to using canines in clinical studies. Rodents, not previously used for such studies, were demonstrated to be excellent mammals for testing initial electrode modification strategies. Myocardial tissue resistance in a living mammalian heart was determined using chronoamperometry and cyclic voltammetry of Ru(NH3 Pacemaker systems represent complete electrochemical cells. Thus, modified pacemaker electrodes are simply examples of chemically modified electrodes, an area of electrochemistry which has been studied extensively over the past two decades. For these types of systems, the interfacial chemistry occurring in the vicinity of the SAM is crucial to its function. Therefore, investigations into the stability, order, and orientation of SAMs at the metal electrode surface, and solvent behavior at the outer edge of the SAMs were undertaken. Such fundamental information is critical in understanding the biocompatibility of these modified pacemaker electrodes, and potentially, in understanding the mechanism for the pacing efficacy of the electrode modification. Surface Raman spectroscopy using an emersion approach was developed as an exceptional technique for probing the structural order and stability of SAMs on Ag and Au after exposure to solvent, electrolyte, and potential. Finally, the stability of these SAM-modified pacemaker electrodes to air and mechanical stress was investigated. Raman spectroscopy, cyclic voltammetry and x-ray photoelectron spectroscopy were utilized to better understand the shelf-life of modified electrodes.

Every day, billions of senescent human erythrocytes are removed from the circulation. The mechanism of recognition involves the formation of a neo-antigen on senescent cells, which binds autologous immunoglobulin and targets the senescent cell for phagocytosis. This neo-antigen is derived from an existing integral membrane protein, band 3. The molecular mechanisms underlying the formation of this neo-antigen during the aging process are poorly understood, but oxidative damage is suggested to be a critical event. Several post-translational modifications have been associated with aging that may contribute to altered antigenicity of the band 3 molecule, either directly by forming a covalent modification that contributes to the neo-antigen epitope or indirectly by altering the conformation of the protein, exposing hidden epitopes. Tandem mass spectral analysis was performed on tryptic digests of the band 3 protein from young and old erythrocytes. Six oxidations of methionyl residues were detected, one of which lies adjacent to a region of band 3 proposed to form an epitope of the neo-antigen and one of which lies between proposed antigenic regions. Studies of vitamin E deficiency and supplementation strongly support oxidation as a pivotal event in alteration of band 3 with aging, and the oxidized methionines identified in this study may represent the critical sites of damage. A possible deamidation was also identified in an antigenic region of band 3. Deamidation is suggested to serve as a molecular timeclock for proteins, and conversion of a glutamine to a glutamic acid may alter the antigenicity at this critical region of band 3. This work represents the first application of tandem MS/MS methodologies to a large integral membrane protein. Forty-four of the 75 band 3 tryptic peptides were characterized, covering 61% of the band 3 polypeptide. Many of the tryptic peptides did not meet criteria for proper peptide analysis. Of the remaining peptides, 95.3% of the band 3 molecule was characterized, with 55% sequenced by MS/MS. Since only partial sequence information is expected for this type of analysis, these percentages represent a tremendously successful application of the technique.