Water-in-oil reverse-phase microemulsions were studied to determine the effects of changing the concentrations of the components of the microemulsions on the shape, sizes, and interactions of the particles of the microemulsion system. Two fluorescent probes were used in the measurement and analysis of bis(2-ethylhexyl) sulfosuccinate (AOT) water in octane reverse phase microemulsions. Dansylpiperidine and 9-aminoacridine were chosen as the fluorescent probes used in the analysis. The experiment consisted of the analysis in solvents of differing polarity, AOT microemulsion solutions of various water, surfactant, and octane ratios, and four component microemulsions. The four component microemulsions consisted of solutions containing AOT, water, octane and tertiary butyl alcohol. The resulting spectra of the fluorescent probes within the various microemulsion solutions were compared to those of the solvent series to analyze the effects of changing local environment on the fluorescent species and to give a comparison of the polarity of the environment in which the probe was located. The different regions of the microemulsions system had very different polarity characteristics, which were observed and analyzed through the fluorescent signals of the probes within the microemulsion system. The effects on the inner water core of the emulsion, the interface of the surfactant molecules with both solvents, and the outer organic phase (by changing the concentrations of the microemulsion components) were determined and are presented in the following paper.

The need in organic synthesis to replace hazardous organic solvents with green solvents led to the development of ionic liquids (ILs) as alternative solvents. ILs are molten salts (melting points less than 100&deg；C) and are typically comprised of a poorly coordinated bulky cation and smaller anion. We have examined ILs for their solvent-electrolyte properties using electrochemical techniques including cyclic voltammetry (CV) and chronoamperometry. The ILs studied were trialkylmethylammonium methylcarbonate salts synthesized using green synthetic methods whereby quaternization of tertiary amines was achieved with dimethylcarbonate under high pressure and temperature conditions instead of a methyl halide. The purity of ILs was examined using cyclic voltammetry and the results of low levels of amine impurity were further confirmed from mass spectrometry. Further investigations demonstrated that oxidation of ferrocene by CV was irreversible due to reaction of the ferrocenium cation with the methylcarbonate anion. Ferrocene reversibility was achieved when the methylcarbonate anion was replaced with tetrafluoroborate anion. Our investigations also focused on the proton donating capability of water in the ILs using p-benzoquinone as our proton probe. The electrochemical behavior of p-benzoquinone is different for aprotic and protic solvent system which acts as the basis for its proton probe activity. The p-benzoquinone in aprotic solvent system produces two reversible electron transfer reduction waves in cyclic voltammetry (formation of a radical anion for the first wave and a dianion for the second wave). In aqueous solvents, the reduction of p-benzoquinone is a single reversible two electron, two proton process (formation of p-hydroquinone). Instead of two separate reduction waves, one two-electron reduction wave is observed. As water is added to nonaqueous solvent, the two single electron reduction waves coalesce into one two-electron reduction wave.

The discovery of microRNAs miRNAs) and their abilities to regulate in vivo protein synthesis have led to growing interests in miRNA research. Due to their functions on regulating cellular processes that are related to diseases such as cancer, miRNAs can potentially become a new class of diagnostic biomarkers and therapeutic agents. Since early 2000, researchers have reported more than 1,000 human miRNAs. To facilitate high-throughput clinical studies, there are needs for more accurate and robust analytical methods to detect and quantitate miRNAs. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry MALDI-TOF MS) has been used mainly for proteomics research. In the past two decades, MALDI-TOF MS has also been used in genomics research. Specifically, MALDI-TOF MS has been used in the analysis of oligonucleotides, both DNA and RNA. In this study, the use of MALDI-TOF MS to detect specific miRNA was optimized, and the applicability of tandem MALDI-TOF/ TOF to perform partial de novo sequencing was evaluated. The MALDI process requires a small organic compound, often known as “matrix”, which readily undergoes desorption on contact with UV laser and assists the ionization of analyte. Therefore, an investigative study was designed to compare five commonly used MALDI matrix compounds for oligonucleotide analysis. The selected matrix compounds includes 3-hydroxypicolinic acid 3-HPA), 2,3,4-trihydroxy-acetophenone THAP), 6-aza-thiothymidine 6-ATT), 3,4-diaminobenzophenone DABP) and 3-hydroxycoumarin 3-HC). The goal is to identify which is the best matrix for supporting the MALDI process and the subsequent tandem MALDI-TOF/TOF measurements. The 4700 Applied Biosystems Proteomics Analyzer was initially used to perform linear MALDI-TOF MS analysis of a selected microRNA standard miR-124a). The initial results of our MS/MS measurements indicated higher signal intensity or ion count of the parent ion of miRNA is required to achieve sequencing. For this reason, we embarked on a series of studies to increase the signal intensity, especially on the effects of various parameters that were related to the desorption of miRNA during the MALDI process. The results indicated 3-HPA matrix has provided the highest signal intensity. Thus, 3-HPA was used to further optimize the MALDI-TOF MS measurements of miRNA. Once the parameters of MALDI-TOF MS were optimized, the use of tandem MALDI-TOF/TOF MS to perform partial de novo sequencing of miRNA was evaluated. Following the acquisition of initial MS/MS spectra of miR-124a, the use of different collision-induced dissociation CID) pressures and delayed times to induce the fragmentation of miR-124a parent ion were investigated. It was determined that the 4700 Proteomics Analyzer could have a limitation on measuring the singly-charged miR-124a parent ion 7,161 m/z). This could be due to the current design and/or settings on the reflectron within the MALDI-TOF/TOF instrumentation were not suitable for measuring ions with high molecular masses. To overcome this limitation, the doubly-charged miR-124a parent ion 3,582 m/z) was selected as an alternative for performing the tandem MALDI-TOF/TOF MS measurements. Both post-source decay PSD) and CID in the positive ion mode were used.

Planar array infrared (PA-IR) spectroscopy has recently been employed as an alternative to Fourier transform infrared (FT-IR) spectroscopy for studies involving dynamic chemical events. At the onset of this thesis, most PA-IR instruments were grating-based, which typically provided a sufficient spectral resolution but a poor spectral coverage. The results of this thesis demonstrated that prism-based spectrographs can be viable alternatives to grating-based spectrographs when spectral coverage is more important than spectral resolution. Chapter 1 serves as an introduction into FT-IR and PA-IR spectroscopy. Chapter 2 focused on the development of macroscopic transmission prism-based spectrographs, Chapter 3 evaluated the performance of an attenuated total internal reflection (ATR)-PA-IR spectrograph, Chapter 4 investigated the potential for PA-IR microspectroscopy and Chapter 5 employed ATR-PA-IR spectroscopy as a detection technique for liquid chromatography. Chapter 6 deviates slightly from the rest of this thesis and involved comparing macro ATRFT- IR and micro ATR-FT-IR imaging for the analysis of counterfeit pharmaceutical tablets.

The works presented are a study of the fundamental interactions of molecular electronic schemes using Scanning Tunneling Lithography and Electrochemistry. Through the use of Self-Assembled Monolayers (SAM) the desorption, adsorption, and replacement of molecules on gold, platinum, and palladium substrates were characterized. SAMs were electrochemically desorbed and monitored via Faradaic response. Replacement Lithography was used to selectively replace portions of the SAM to explore changes in the conductivity of the replaced region. Through the use of apparent height response the replacement of SAMs were monitored. The contributions of chemically bound functional groups to the substrates were then characterized by apparent height response.

In-situ Raman spectra of solution phase electrogenerated species were recorded in a channel flow cell. A microscope objective aligned normal to the direction of flow downstream from the edge of the working electrode was used to focus the excitation laser beam near the metal-electrode|electrolyte interface and also to collect the Raman scattered light from electrogenerated species under maximum detection sensitivity. Linear correlations were found between both the gain and the loss of the integrated Raman intensity attributed to the active redox species, and the current measured at the working electrode as a function of potential. Light-activated microelectrodes in redox electrolytes were modeled theoretically using COMSOL under strict axisymmetric geometry. Dimensioned and dimensionless steady state profiles for solid state and solution phase species were predicted by solving self-consistently the transport equations and the electrostatic potential within the semiconductor phase subject to the appropriate boundary conditions. The local flux at the interface in the direction normal to the semiconductor surface was calculated as a function of photon flux intensity and bias potential. The predicted limited currents were proportional to the photon flux intensity under high bias potential, the simulation results showed that photo-generated holes in an n-type semiconductor would escape beyond the edge of the illuminated disk, thereby increasing the effective area of the light-activated microelectrode. The effect of the shape on properties of electrocatalytically active nanoparticles supported on inactive planar substrates was modeled theoretically. The results indicated very minor differences between the diffusion limited currents, ilim, for reaction on a hemisphere and full sphere with the same area. However, for prolate spheroids large enhancements were predicted as the aspect ratio was increased. Analyses of the predicted behavior of active microdisks dispersed on both planar and spherical inactive substrates suggested that currents very close to ilim could be achieved for coverage on the order of 1%. This effect might explain experimental observations for the onset potential for the oxygen reduction well ahead of the onset of the reduction of iron porphyrins adsorbed on carbon surfaces associated with the conversion from the inactive to the active form of the macrocycle.

The work described in this thesis focuses on FT-IR and quantum cascade laser QCL) based studies towards the development of compact and portable trace gas sensor for benzene, toluene, and xylenes BTX). In the first part of this thesis, FT-IR broadband radiation was used to probe the mid-infrared fingerprint region for quantitatively detecting trace gas levels of BTX. Using direct absorption through a hollow waveguide, parts-per-million ppm) detection limits for BTX with a response time of 39 seconds was demonstrated. Univariate calibration provided limits of detection 3sigma) for benzene, toluene, and meta-xylene at 5, 17, and 11 ppm, respectively. Multivariate calibration using partial least squares regression algorithms were used to simulate real-world conditions with multiple analytes present within a complex sample. A calibration model was built with 110 training set standards enabled by using a customized gas mixing system. To lower detection limits toward environmentally more relevant concentrations, a preconcentration/thermal desorption TD) step was added to the FT-IR HWG trace gas sensor enabling parts-per-billion detection of BTX. A univariate calibration was established in the laboratory with certified gas standards over a dynamic range of 1000–100 ppb for benzene, toluene, and the xylenes. The sensor was then taken to an industrial site during a field measurement campaign for the quantitative determination of BTX in field air samples. The laboratory calibration was used to predict unknown concentrations which were in close agreement with industrial hygiene standard techniques, and industrial prototype analyzers, that were simultaneously operated in the field environment. Independent validation of the obtained results was performed via GC-FID analysis. Further optimization of the experimental parameters finally resulted in the reproducible detection of 5 ppb benzene with the developed TD-FT-IR-HWG sensing device. The second part of this thesis was focused on quantum cascade lasers and their role in trace gas sensors in an effort to miniaturize future IR gas sensing platforms. Particlar efforts were dedicated on a novel principle for consistent and deliberate QCL emission wavelength selection by varying the QCL cavity length. These studies experimentally confirmed that using this straight-forward post-processing technique, emission wavelength tuning across a range of one hundred wavenumbers range may be achieved. This tuning range was experimentally demonstrated for a QCL emitting across an entire absorption feature of carbon dioxide by tailoring the length of the cavity. Additionally, using an external cavity EC)-QCL combined with a HWG gas sensor module for the first time enabled the quantitative and simultaneous determination of ethyl chloride, trichloromethane, and dichloromethane within exponential dilution experiments at ppb limits of detection. Multianalyte detection was demonstrated utilizing partial least squares regression for quantitative discrimination of individual constituents within a mixture, yet applying a single broadly tunable QCL light source. Finally, an outlook is provided for continuing research in this field toward further miniaturization of the sensing platform established within this thesis e.g. by evaluating the feasibility of coiling HWGs. Furthermore, current limitations for obtaining QCLs lasing at longer wavelengths—as required for BTX analysis—are discussed, as well as the potential future of QCL based trace gas sensors for BTX.

Organic contamination on spaceflight hardware is an ongoing concern for spaceflight safety. In addition, for the goal of analyzing for possible evidence of extra-terrestrial life, it is necessary to consider the presence of terrestrial contamination. This paper will introduce and evaluate a new method using a direct analysis real time DARTTM)) ionization source paired with a high resolution time of flight mass spectrometer TOFMS) for the determination of organic contamination involved in spaceflight hardware and ground support materials. This novel analytical technique has significant advantages over current methodologies. Materials analyzed in this study were historically considered as probable contaminants in spaceflight related substrates. A user determined library was generated due to the non-traditional mass spectra generated by the DARTTM). Continual improvement of analytical methods for the detection of trace levels of contaminants in potential drinking water sources is of extreme importance to both regulatory communities and concerned citizens. This paper will evaluate a novel analytical method using stir bar sorbtive SBSE) extraction techniques combined with analysis with a DARTTM) TOFMS. Compounds of interest will include several representative pharmaceutical contaminants of emerging concern listed in EPA method 1694. Optimal SBSE and DARTTM) experimental parameters will be investigated along with accuracy, precision, limits of detection and calibration linearity.

Small-molecule profiling, termed metabolomics, is a valuable tool to study phenotype and changes in phenotype caused by environmental influences, disease, or changes in genotype. The metabolome can be defined as the complete complement of all small molecule &lt；1500 Da) metabolites found in a specific cell, organ or organism. The metabolome represents a vast number of components that belong to a wide variety of compound classes, and these compounds are very diverse in their physical and chemical properties and occur in a wide concentration range. Consequently, studying the metabolome is a major challenge to analytical chemistry. Mass spectrometry MS) is used in metabolomics to detect, quantify, and identify enzymatic substrates and byproducts from biological and clinical samples. MS-based metabolomics offers qualitative and quantitative analyses with high selectivity and sensitivity, wide dynamic range, and the ability to analyze biofluids with extreme molecular complexity. The combination of liquid chromatography with MS reduces the complexity of the mass spectra, decreases ion suppression, provides isobar resolution, and delivers information on the properties of the metabolites. In this study, the hypothesis that detectable changes will occur in the blood plasma metabolic profile of healthy female and male adults before and after a ketogenic diet has been tested. In addition, changes in the plasma metabolome of piglets between days 2 through 8 of life have been evaluated. Novel complementary chromatographic approaches–reversed phase and hydrophilic interaction liquid chromatography, directly coupled to a time-of-flight mass spectrometer operating under electrospray conditions in positive ion mode, have been developed and optimized. The performance/contribution of each separation strategy, identification of unique m/z features, and technical variability have been evaluated. The studies involved a large number of samples that required powerful data processing/analysis capabilities. In this sense, the raw data were processed using commercial instrument software. From the obtained chromatograms, features were extracted, aligned, normalized, filtered, and then analyzed by different statistical methods, including analysis of variance, principal component analysis, and volcano plots. Finally, using the accurate mass criterion of 2 ppm mass error, putative biomarkers responsible for the metabolic differences in the samples were identified using several databases.

With the development of higher field magnets and capabilities of spinning samples at greater speeds, high resolution solid-state nuclear magnetic resonance SSNMR) spectra of quadrupolar nuclei resolving multiple spectroscopic sites in a sample are now attainable, where just two decades ago it would not have been possible. With these advances, the field of SSNMR has truly been opened to determination of structure in inorganic materials, which are mainly quadrupolar nuclei. Although, many obstacles to obtaining structural information using SSNMR have been overcome, there are still issues, such as small sample size, poor sensitivity small gyromagnetic ratios, low natural abundance) and long relaxation times. In this thesis, I will discuss methods of obtaining high resolution spectra of quadrupolar nuclei using a theoretical description of interactions to second-order that may contribute to the NMR spectra of quadrupolar nuclei and provide a method to remove or isolate such interactions. This description is not only useful for describing experiments currently utilized, but lays the groundwork for the development of new experiments. With some experiments and samples, a theoretical approach beyond second-order is required to analyze spectra, an outline to use exact numerical calculations to simulate NMR spectra is also given. To combat the low sensitivity and to decrease experimental time, preparatory enhancement sequences that increase the sensitivity of spectra are necessary. A method to ensure optimum enhancement when utilizing these experiments is given. Using these techniques, I will give insight on the structure of densified amorphous silica. I have measured the two-dimensional 17O dynamic-angle spinning solid-state nuclear magnetic resonance spectrum of silica glasses produced from the melt and densified in a multi-anvil device at pressures up to 15 GPa. From the spectra, two-dimensional histograms correlating Si-O-Si angle with Si-O distance, Si-O-Si angle with Si-Si distance, and Si-O distance with Si-Si distance are derived.