Master of Science (MS), Wright State University, 2007, Chemistry

Stinson, Jelynn Anneula. M.S., Department of Chemistry, Wright State University, 2007. The Electroanalytical Performance of Sonogel Carbon Titanium (IV) Oxide Electrodes versus Conducting Polymer Electrodes in the Electrochemical Detection of Biological Molecules. The electrochemical performance of a newly developed sonogel carbon titanium (IV) oxide (SGC/TiO2 ) electrode against poly(3-methylthiophene) (P3MT) and poly(2,2'-bithiophene) (PBTP) modified electrodes in the electrochemical detection of biological molecules is reported. The stability of the Titanium (IV) Oxide coating on the sonogel carbon electrode was shown to be greater than the P3MT coating on the conventional size glassy carbon electrode. After 10 consecutive scans, there was a 21% loss of the initial signal at the P3MT modified electrode and a 5% loss of the initial signal at the SGC/TiO2 electrode. The influence of NAD+ on NADH response was tested. The PBTP modified electrode and bare electrode demonstrated the inability to stabilize the interference due to NAD+. The SGC/TiO2 electrode was able to detour the susceptibility to interfering NAD+. The response potential was improved by 141 mV. Response time for 5mM catechol (CAT) and 5mM ascorbic acid (AA) in 0.01M sulfuric acid was determined. Specificity for CAT detection was measured using a 5mM CAT + 5mM AA mixture in 0.01M sulfuric acid. The SGC/TiO2 electrode permits a shorter response time and improved selectivity for CAT. NADH was irreversible in all electrolytes. Highest anodic peak potential, at the PBTP modified electrode, was measured in sodium nitrate. Highest anodic peak potential at the SGC/TiO2 electrode was recorded in sulfuric acid.

Committee: Suzanne Lunsford (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

This dissertation comprises of two parts, each discussing different aspects of cyclodextrin chemistry. The research has been performed in an effort to further investigate inclusion properties of cyclodextrins and demonstrate their practical utilization in analytical chemistry. In the first part of the dissertation, cyclodextrin complexes of α- and β-cyclodextrin with nonionic surfactants containing linear alkyl and oligooxyethylene residues are the subject of fundamental research. Several techniques were employed for the determination of the complex stoichiometry and calculation of the stability constants. While UV-Vis spectrophotometry and NMR provided qualitative description of the structure of inclusion complexes, other techniques, such as titration microcalorimetry and capillary electrophoresis, yielded more quantitative data. The second and the third chapter will describe inclusion complexes between C 12 E 6 , and α- and β-CD, respectively. The effect of benzoate on the stability constants of these inclusion complexes was investigated and evidence of ternary complexes will be presented. The fourth chapter is primarily focused on the investigation of the interactions of a homologous series of nonionic surfactants C x E y containing a linear hydrocarbon, in an effort to establish some structural parameters that could affect the strength and the stoichiometry the interaction with both, α- and β-CD. In the second part of this dissertation, application of sulfated β-cyclodextrin to capillary free flow electrophoretic (CFFE) chiral separation is discussed. In recent years, there has been an effort to develop alternative preparative scale chiral separations. Cyclodextrins have proven to be an effective chiral selector, providing a medium for successful chiral separations. Fundamental principles of preparative scale electrophoretic separations will be presented. The concentration distribution of sulfated β-CD, determined in-situ within the CFFE separation chamber, will (open full item for complete abstract)

Committee: Apryll Stalcup (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

Adequate identification and quantification of elemental species in the environment are necessary to completely assess their potential toxicity. Inductively coupled plasma - mass spectrometry (ICP - MS) coupled to chromatographic separation is a widely used, highly sensitive detector. For samples to be analyzed by ICP - MS, they must first be extracted into a solution capable of being nebulized into the ICP. A variety of extraction procedures were evaluated for the extraction of arsenic and other analytes from lobster tissue samples using ICP - MS detection. Room temperature mixing, sonication, soxhlet, microwave assisted, supercritical carbon dioxide and subcritical water extractions were evaluated for a variety of solvent systems and optimum conditions determined using a partially defatted Lobster Hepatopancreas marine reference material (TORT-2, National Research Council of Canada). Microwave assisted extraction (MAE) yielded comparable or improved recoveries for all of the analytes monitored and proved to be the mildest, fastest, least complicated and most reproducible extraction technique. MAE at 75 °C for 2 minutes exposure time yielded quantitative recovery of arsenic from TORT-2 and lobster tissue samples purchased from a local restaurant A novel gradient anion exchange chromatographic technique was developed that allows the speciation of arsenobetaine (AB), arsenocholine (AC), arsenite (As III), arsenate (As V), monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) in ~ 27 minutes using ammonium carbonate buffer. Low detection limits, excellent long-term stability and baseline resolution of all of the arsenic species evaluated were achieved when the ratio of AC:AB was less than ~ 12.5:50. This technique was successfully applied to TORT-2 and lobster tissue samples. AB was the major arsenic species identified. AC, DMAA, AS V and unknown peaks, possibly arsenosugars, were also found. Methanol and isopropanol were evaluated as extraction solvents for a (open full item for complete abstract)

Committee: Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

The concept of spectroelectrochemistry using an ATR system has been explored in our research group for a number of years. To date the concept of achieving a sensor with multimodes of selectivity has been demonstrated with potassium ferrocyanide, Ru(bipy) 3 2+ , and Ru(CN) 4 - . This sensor has three modes of selectivity: applied potential, chosen wavelength and chemically selective film. In this sensor device in order for an analyte to be detected it must first partition into the sensing film, be electroactive at the applied potential, and have a change in absorbance at the wavelength of light. In the first part of my research, I evaluated expanding the sensor concept to detect an analyte which itself did not undergo electron transfer at the electrode and which is not optically monitored. To explore this system a mediated electrode reaction was used in which the mediator undergoes spectroelectrochemical modulation. The analyte is detected indirectly by its effect on theoptical signal from the modulated mediator. The system explored was that of ascorbic acid as the analyte and Ru(bipy) 3 2+ as the mediator using a composite film of Nafion-SiO 2 . Factors such as scan rate, concentration of mediator in the film, film composition and thickness, and analyte solution pH was studied to achieve optimal sensor conditions. This concept can be further expanded in developing a biosensor. This concept was explored using mediated detection and the addition of an enzyme. Investigation into to developing a more selective glucose biosensor was explored as well as several different mediators for this reaction. The final part of my research was development of a sensor capable of determining the concentration of technetium in various chemical forms (mainly pertechnetate) in the vadose zone and ground water at the U.S. DOE Hanford site. In this research Re and Mn are being used as a chemical surrogate for radioactive Tc. The chemical and electrochemical reduction of ReO 4 - , and MnO 4 (open full item for complete abstract)

Committee: W. R. Heineman (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

A comparison of capillary electrophoresis (CE) migration times using standard on-column UV detection and inductively coupled plasma - mass spectrometry (ICP-MS) is presented for two different CE separations. The first is a separation of five arsenic compounds, four anionic species and one neutral, using reverse polarity in a chromate buffer with an electroosmotic flow modifier. The second CE separation employs normal polarity for the separation of eleven lanthanide cations using a HIBA buffer with an indirect UV detection reagent. Migration times observed for CE-ICP-MS electropherograms are comparable to migration times acquired with UV detection, and may be adjusted by changes in the make-up liquid level position. The precision of peak areas (<2%) and migration times (<4%) obtained using CE-ICP-MS is comparable to that obtained using online UV absorbance detection. CE-ICP-MS limits of detection are in the low ng ml-1 range for the analytes studied. Then, CE is coupled on-line to a double-focusing sector field inductively coupled plasma-mass spectrometer (DF-ICP-MS) for the analysis of mixtures of lanthanide elements in aqueous samples with natural isotope abundances and in a sample taken from an irradiated tantalum target particle reactor containing artificial nuclide abundances. Detection limits for the most abundant isotopes of lanthanides were 0.1ppb to 5 ppb, an improvement of as much as one order of magnitude compared to a quadrupole ICP-MS system. Abundances for the most abundant isotopes of lanthanides were found to be within 0.1 - 2% of table values for natural samples while isotopes present in smaller amounts were within 3 - 5% of table values. CE-ICP-MS is also used for the chiral speciation of DL-selenomethionine using Marfey's reagent for chiral derivatization and applied to selenized yeast samples extracted with Proteinase K. Finally, two anion exchange chromatography systems were interfaced to ICP-MS for determination of bromate in ozonated drinking w (open full item for complete abstract)

Committee: Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

Three types of electrochemical sandwich microimmunoassays have been developed using paramagnetic microbeads for the heterogeneous surface and mouse IgG for the model analyte. In all three, the enzyme label alkaline phosphatase (ALP) was used to convert the substrate 4-aminophenyl phosphate (PAPP) into the electroactive product 4-aminophenol (PAP). The assay incubations were carried out in microwells with earth magnets used to separate the beads from the supernatant during rinses. Since adapting the detection schemes widely used in electrochemical immunoassay (i.e., FIA-EC and LC-EC) proved difficult for bead-based assays, three new detection schemes were developed. In the first method, a rotating disk electrode (RDE) was applied on a microdrop of PAPP to which the beads were added for detection. Direct analysis in a microdrop minimizes the PAP dilution, a key requirement in achieving very low detection limits. Furthermore, the detection scheme allowed enzyme turnover to be monitored continuously, thus shortening the detection time and reducing the errors associated with obtaining data at fixed times as in FIA-EC. A non-optimized calibration curve for mouse IgG was obtained from 50 to 5000 ng/mL with detection times of less than a minute. In the second method, scanning electrochemical microscopy (SECM) was used to detect the electroactive product generated over microspots of beads. This approach was first demonstrated with beads coated with mouse IgG-ALP conjugates. Detection was carried out in the SECM generation-collection mode by oxidizing PAP formed over the microspots. The signal height correlated with the amount of beads present in the microspot. Next, the SECM feedback mode was used to image streptavidin-coated beads that were labeled with biotinylated glucose oxidase. Finally, working with microspots with a top-view radius of 75 microns, a miniaturized sandwich assay was carried out, and a detection limit of 1.5 x 10 -15 moles of mouse IgG was obtained. In th (open full item for complete abstract)

Committee: William Heineman (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2001, Arts and Sciences : Chemistry

Statistical methods for the optimization of chemical procedures are a more appropriate approach compared to the univariate optimization. A factorial design was used for a slurry preparation in the determination of five different elements with ICP-AES determination. The chiral separation of nine selenoaminoacids using a crown ether HPLC column coupled to ICP-MS for detection is described. Three different temperatures were investigated for the separation of the enantiomers of individual amino acids and for a mixture of eight selenoamino acids. Although complete resolution was not achieved, better resolution of the mixture was obtained at higher temperatures. Selenium enriched onion; garlic and yeast were also analyzed. Two different extraction methods for the samples are compared, and some of the selenoamino acid enantiomers are identified. Comparison is also made with earlier reported separations for some of these selenoamino acids. Several procedures to perform selenium enrichment of yeast have been evaluated in the present work in terms of yeast cell growth protocols, total selenium accumulation, and to a limited degree, selenium species formation. Four enrichment procedures have been evaluated using sodium selenite as the selenium source: a) enrichment during the growth phase, b) enrichment at the non-growth phase; both of these at different selenium levels, c) enrichment by seeding in a fermentable carbon source (glucose) and d) enrichment by using non-fermentable carbon source (glycerol). A nitric acid digestion of the yeast has been performed in order to evaluate the total selenium incorporated into the yeast cells. Also, an enzymatic digestion of the yeast samples with pepsin has been carried out as an initial step to begin the process of determining which of the different possible selenium species are formed. The release of different selenium compounds during a normal human selenized yeast digestion is not known and animal and human studies have established t (open full item for complete abstract)

Committee: Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2000, Arts and Sciences : Chemistry

Liquid sample introduction with inductively coupled plasma-mass spectrometry (ICP-MS) can be a key issue in the development of separation techniques used for elemental speciation. A two-tube oscillating capillary nebulizer (OCN) was developed and evaluated for interfacing both high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). The chief theoretical advantage of the OCN is in its low flow operation which makes it well suited for the ICP. A number of commercial nebulizers and spray chambers were compared to the developed OCN equipped with a single pass spray chamber; all nebulizers were compared using ion-pair HPLC conditions. Observed detection limits for arsenic compounds separated were 160 to 360 ppb for the OCN verses 2.0 to 11 ppb for the conventional nebulizer combinations using a small bore (2 mm ID) column. Also, a microbore (1 mm ID) column using a commercial micronebulizer produced low detection limits for the arsenic compounds. Capillary electrophoresis is a low flow separation technique and is well suited for low flow nebulizers. All pneumatic nebulizers, however, have a problem with interfacing with CE. The aspiration generated by the nebulizer can greatly affect the flow rate through the capillary and compromise the CE separation. Different designs of CE OCN interfaces were tried using UV detection as a scouting technique. The use of a permeable frit in the sample side of the capillary was used to evaluate the OCN for possible ICP-MS interface. The novel concept of the fritted capillary was ultimately conducted on a more conventional micronebulizer. The application of elemental speciation to actual samples not previously studied was performed. Freeze-dried apple samples were studied for trace levels of various arsenic compounds using ion-exchange HPLC interfaced to the ICP-MS. Total arsenic levels of three apple samples were determined, as well as an evaluation of extraction techniques used for speciation. Finally, reversed (open full item for complete abstract)

Committee: Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2000, Arts and Sciences : Chemistry

Incorporation of planar waveguide technology into spectroelectrochemical sensors with trimodal selectivity (partitioning, electrochemistry and spectroscopy) is described. The main advantage of planar waveguides is enhanced sensitivity due to the increased number of reflections over a multiple internal reflection (MIR) optic. Three planar waveguide designs have been fabricated and evaluated. In order of discussion, the three waveguide candidates are 1. an indium tin oxide (ITO) coated K+/Na+ ion-exchanged BK7 graded-index slab 2. an ITO coated GeO2-SiO2 step-index slab and 3. a gold coated K+/Na+ ion-exchanged BK7 graded-index channel. ITO or Au served as the electrode. The first candidate was selected since this design most closely resembled the prototype MIR optic, with which the sensor concept was successfully demonstrated earlier. In choosing GeO2-SiO2 as one of the waveguide designs, we wanted to reapply this telecommunication-oriented material for chemical sensing, especially in the near-UV wavelength region. The channel waveguide was of interest because of its possible microfabrication. In addition to the waveguide designs, alternative coupling methods to prism couplers were explored. Based on the fabrication scheme of Ramos, Choquette and Fell (Anal. Chem. 1996, 68, 1245), an embossed UV-cured polymer grating has been made and showed excellent results compared with our current sensor that is prism-coupled. Evaluation of the waveguide candidates was two-part: optical and spectroelectrochemical. We compared the optical properties, such as the refractive index, and the number of modes, at a near-UV wavelength of 441.6 nm (HeCd laser) for optical sensing of Fe(CN)6-3, a benchmark analyte in the demonstration of the selectivity concept, and at 632.8 nm (HeNe). All the waveguides that were fabricated were found to be multimode (3-5 modes) at both wavelengths. For demonstration of electromodulation of the optical signal with all three waveguide sensors, the chosen r (open full item for complete abstract)

Committee: Carl Seliskar (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2000, Arts and Sciences : Chemistry

Presented in this work are speciation techniques which have been developed for a cupric azo dye, arsenic extracted from fish, and copper and chromium compounds. The organometallic dye Direct Red 83 was subjected to speciation using HPLC coupled with inductively couple plasma mass spectrometry to determine the percentage of copper which is not bound to the dye. This "free copper" made up 13% of the total copper present in the sample. An automated extractor employing accelerated solvent extraction (ASE) has been compared with a traditional sonication method of extraction, for the extraction of arsenicals from fish tissue. Extracted arsenicals were speciated with chromatographic separation and ICP-MS. Both extraction methods produced extraction efficiencies of greater than 71% with RSDs on replicates of less than 5.5%. The chromatographic separation employed a PRP-X100 anion exchange column. The speciation data indicates that the predominate species were arsenobetaine and arsenocholine. Optimization of the automated extraction method indicated that the parameters which had the greatest influence on the recovery of arsenic were sample particle size, dispersion of the sample, and extraction time. Grinding of the sample with a mortar and pestle in a high density glass bead dispersion media produced extraction efficiencies of 88%, 92%, 98%, and 103% for whitefish, shark, tuna, and salmon respectively. Separation methods revealed that in all of the extracts, arsenobetaine (AsB) represented greater than 79% of the arsenic concentration present. Electrospray mass spectrometry (ESMS) has been used to provide both elemental and structural information for chromium (II) acetate, chromium (III) acetylacetonate, and copper (II) acetylacetonate. The electrospray interface, constructed in house, provides control over the ionization conditions, applied potentials and gas curtain flow rates. This enables the operator to tune the conditions to produce elemental spectra, or spectra which (open full item for complete abstract)

Committee: Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

Research directed to identify compounds containing selenium and their chemical and biochemical pathways in the environment and in organisms has gained momentum in recent years, in part owing to the ability of selenium compounds to serve as cancer-preventive agents. Even though an extensive knowledge of small molecules containing selenium has been obtained and analytical methodologies to analyze small molecules containing selenium are well established, the wealth of knowledge regarding selenoproteins is limited except in a few selenoproteins such as glutathione peroxidase. Even in studies in which selenoproteins were analyzed in detail, the method of analysis has been based on the classical biochemical approach-one protein at a time. This dissertation describes the analysis of selenium containing proteins based on the proteomics approach. Bertholletia excelsa (Brazil nut) which has been identified to be rich in selenoproteins is used as the source of selenoproteins. In chapter one, chromatographic methods of analysis and three critical mass spectrometric techniques employed in selenoproteomics research, namely ICPMS, MALDI MS and ESI-MS are briefly described. Chapter two describes the factors affecting the selenium isotope pattern-the most important observation in identifying peptides containing selenium. The manner in which the isotope pattern changes with the molecular weight of the peptide, the number of selenium atoms in the peptide, the effect of post-translational modifications and the instrumental parameters such as the resolving power of the mass spectrometer and chromatographic separation conditions, is presented in detail. In chapter three, analysis of selenium-containing proteins in Brazil nuts is described, demonstrating the way the different experimental methodologies affect the outcome of the analysis, and highlighting the advantages, disadvantages as well as limitations of the analytical methodologies employed. Chapter four presents the usefulness of f (open full item for complete abstract)

Committee: Dr. Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

Pseudouridine, the most abundant post-transcriptional modification in RNA, was derivatized with the water-soluble carbodiimide, N-cyclohexyl-N'-a-(4-methylmorpholinium) ethylcarbodiimide (CMC). Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was utilized as the mode of detection for CMC-derivatized pseudouridine. Initial studies involving method optimization were conducted on a simple homopolymer and heteropolymer DNA system. These studies were directed toward optimizing the CMC derivatization reaction conditions and ensuring its compatibility with MALDI-MS. After optimization, the method was applied to the determination of pseudouridine in a small RNA, Escherichia coli tRNATyrII. In addition to pseudouridine, this work revealed that the post-transcriptionally modified nucleoside, 2-methylthio-N6-isopentenyladenosine (ms2i6A) was also susceptible to derivatization by CMC. Method application studies were further expanded to include the detection of pseudouridines in a complicated mixture of E.coli tRNAs. For the complex mixture of tRNAs, endonuclease mapping and a signature digestion product approach was implemented with the CMC derivatization / MALDI-MS method for accurate identification and sequence placement of pseudouridine to individual tRNAs in the mixture. Further studies included the application of the CMC derivatization / MALDI-MS method for pseudouridine detection in a large RNA. Preliminary data was also generated from an affinity purification based approach for the detection of CMC derivatized oligonucleotides. These studies reveal the potential utility of the CMC derivatization / MALDI-MS approach as a fast and facile method for screening for pseudouridine in RNA.

Committee: Dr. Patrick Limbach (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

There has been much attention in element specific characterization of metal and metalloid containing species within both environmental and biological systems, over the past few decades. In speciation analysis, an area of research that deals with the detection, identification, and determination of metals, metalloids and their different chemical forms, there have been huge advancements. These advancements are due mainly to instrument technology developments, and new innovative method developments. Hyphenated techniques, based on using ICPMS are among the fastest growing research and application areas in atomic spectroscopy. The combination of ICPMS with high resolution separation techniques presents a unique analytical tool that is able to provide qualitative and quantitative information on species at ultra low levels in complex matrices. Elements such as phosphorus, sulfur, and metals are known to be important atoms in a wide variety of molecules of environmental and biological interest ranging from small molecules to large macromolecules such as proteins. The goal of this dissertation is to characterize phosphorus, sulfur, and metal detection by ICPMS combined with other mass spectroscopy techniques to provide important new information for identifying phosphorus, sulfur, and metal-containing species from low to high molecular weight (MW) from a wide range of sample types. For low MW species the use of elemental and molecular MS techniques were used to demonstrate the viability and enhanced detection capabilities of phosphorus for low MW species (qualitative and quantitative) and illustrated by using organophosphorous fire retardants as samples. For high MW species ICPMS and ITMS in tandem were used for identifying phosphopeptides. Cap-LC-ICP-MS was used for a screening tool for metals in CSF. The simultaneous determination of sulfur in thio-arsenical-containing Rat Urine using HPLC-ICPMS shows, the simultaneous detection of arsenic and sulfur comprised a first repor (open full item for complete abstract)

Committee: Dr. Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

Due to varying properties of an element, depending on its chemical form, total element concentration is often not sufficient information for accurate assessment. Therefore, the analysis of the distribution of an element amongst various chemical species (termed speciation) is critical. By implemented combinations of various separation techniques (namely high performance liquid chromatography (HPLC) and gas chromatography (GC)) with mass spectrometric techniques such as inductively coupled plasma mass spectrometry (ICP-MS) and molecular mass spectrometry techniques, a powerful speciation tool is created. Elemental analysis using ICP-MS and speciation analysis can be used in complement to confirm species recovery and mass balance. When speciation information using HPLC/GC-ICP-MS does not provide enough information, molecular mass spectrometry techniques with softer ionization techniques (able to preserve structural characteristics) can enable confident identification of a given species. Arsenic, selenium, and phosphorus are extremely important elements and are much concern in several fields of research. In specific, arsenic and selenium are of interest due to the drastic difference in toxicity among their respective species. The main goal of this dissertation is to examine the distribution of arsenic, selenium, and phosphorus among various species for assessment of toxicity, nutritional value, and environmental impact. Wheat, potato, yam, and rice samples were examined to establish the impact of their consumption in regards to arsenic content. Selenium association with proteins was examined to further understand its biotransformation in mushrooms. The metabolism of selenium in genetically modified Brassica juncea was examined to further understand the selenium flow of the plant in hopes of creating a more efficient phytoremediation tool. Organophosphorus chemical warfare agent degradation products were chromatographically separated from inorganic phosphate (a common in (open full item for complete abstract)

Committee: Dr. Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

Soil is the main source of essential elements for healthy growth of plants. Contaminated soils lead to accumulation of unwanted chemical species in plants. Thus accumulated species have often been found to show beneficial or detrimental effects on plants and subsequently on their (in)direct predators. Identification of such species is essential for restoring healthy balance in ecological systems. Among various available methods for establishing molecular identity of different species in environment, mass spectrometry (MS) has gained a reputable position. Mass spectrometrists who use inductively coupled plasma (ICP) as ionization source for identification of species have significantly contributed to metal speciation in the environment and other sample compartments. Molecular identity of some small metal species can be achieved by coupling ICP-MS to appropriate chromatography. Owing to high sensitivity of ICP-MS, elements in sub-ppm range can be easily quantified. Suitable sample preparation and pre-concentration techniques can be developed for identification of sub ppb range metal(loid) containing samples. MALDI and ESI equipped MS is useful to establish identity of high molecular weight and novel metal species that lack standards. The above approach was used in this work for metal speciation in food plants. In the process, Se species involved in volatilization pathway of Indian Mustard plant were recognized by ion exchange chromatography. An attempt to identify the mechanism in alleviation of harmful effects of Hg in presence of Se revealed Hg sequestration in soybean roots as a protective mechanism of plants. Further, size exclusion chromatography in conjunction with gel electrophoresis and reversed phase chromatography were useful in suggesting what ultimately may be the first discovered selenoprotein in plants. Modern instrumental methods like capillary and nano-LC were particularly useful in analyzing low sample volumes obtained from selenium enriched sprouts. F (open full item for complete abstract)

Committee: Dr. Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2006, Arts and Sciences : Chemistry

This thesis is dedicated to two separate topics. First topic is related to investigations of the optical properties of spectroelectochemical sensor. The modeling methodology of spectroelectrochemical sensor is described and applied to the Ru(bpy)32+ and Nafion film system. Ru(bpy)32+ sorption is carried out experimentally in a standard sensor configuration. Theoretical absorbance values are obtained for this system based on independently determined optical constants of Nafion film after Ru(bpy)32+ sorption. The developed methodology is applied for studies of thin film ATR spectra. Various thicknesses, pre-soaked Nafion films are studied. Spectral scans over the range of wavelength and angle of incidence reveal significant distortions for films with thickness above 200 nm. Spectra exhibit additional absorbance maxima, shifted considerably away from the true k maxima. The effect is observed if k is on the order of 0.01. Ru(bpy)32+ sorption was studied in situ and by explicit finite difference method. Significant spectral distortions are observed due to leaky waveguiding mode distortions during sorption. The second part of this thesis explores a laser induced fluorescence multi-lane detection system. Plastic materials suitable for optical detection were evaluated over the visible spectrum (403, 488, 532 and 633 nm excitations). Commercially available cyclic olefin copolymers (COC), polycarbonate (PC) and poly(methylmethacrylate) (PMMA) materials and home-made chips are investigated. COC and PMMA and represent the best materials for chip fabrications and exhibit autofluorescence only a few (3 to 5) times higher than Borofloat glass. An optical multi-lane detection system was demonstrated. A linearly expanded beam (~6 mm) was focused across 14 microfluidic channels. As a result, a fluorescent analyte could be detected simultaneously in all channels. Separation of fluorescein and fluorescein isothiocyanate was demonstrated on a glass multi-lane chip.

Committee: Dr. Carl Seliskar (Advisor) Subjects: Chemistry, Analytical

MS, University of Cincinnati, 2006, Arts and Sciences : Chemistry

Seaweeds are found in oceans throughout the world and have been consumed by humans for centuries. There are many commercially available varieties of edible seaweed known for their medicinal properties and food values. However, seaweed can concentrate exceptionally high amounts of heavy elements available from sea, some of which are toxic. Seaweeds have also been used as bioindicators to monitor environmental pollution and for decontamination of some toxic elements from wastewaters [1]. In this study, multielemental speciation analysis of essential and toxic elements in commercially available brown seaweeds such as hiziki and wakame is performed using size exclusion chromatography coupled to inductively coupled plasma mass spectrometry in order to examine the association of trace elements and metals with different molecular weight extracts of seaweed. Total elemental determination using ICP-MS revealed that these seaweeds have high amounts of elements such as As, Sr, Hg, and Zn. Preliminary speciation studies using SEC-ICP-MS reveal that major type of biomolecules responsible for association of these elements in seaweeds are polysaccharides such as alginic acid and fucans. Other biological macromolecules such as proteins and polyphenols also contribute to some extent towards accumulation of trace elements in seaweeds. Other studies have examined trace element concentrations in various extracts of seaweeds but none have analyzed the different trace elements and metals associated with different molecular weight extracts.

Committee: Dr. Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2006, Arts and Sciences : Chemistry

For biological samples, total elemental analysis as well as elemental speciation is especially important. In this dissertation, inductively coupled plasma mass spectrometry is presented as a viable technique for the analysis of total metal content in a variety of sample types. Coupling this method with different chromatography methods allows the different species of these metals to be determined. The study of selenium in yeast has become increasingly important amidst reports of this elements effectiveness in cancer chemoprevention. S. cerevisiae is commonly used to make selenium supplements due to its ability to incorporate relative large levels of selenium into the biologically available form of selenomethionine (SeMet). The investigation of methods that increase this level of incorporation, which maintaining SeMet as the predominant species could be beneficial in the production of such supplements. SeCys, which is incorporated into yeast proteins by specific, rather than non-specific mechanism, is thought to be a biochemically superior form of selenium for cancer chemoprevention. Identifying this compound in specific yeast proteins would be useful in developing more effective antitumorogenic supplements. Metals are very important to the biological function of many organisms. It is expected that this would also be true for viruses, but no comprehensive study of the metal content of viruses has ever been conducted. Likewise, no investigation of cellular metal content during viral infection has ever been reported. By comparing the metal concentrations in healthy cells and HSV-1 infected cells, it is possible to identify elements that are involved or affected by the infection and replication of this virus. Similarly, the metals associated with cancer can be studied by the same techniques. Comparison of metal levels and species in cancerous and non-cancerous lung tissues could provide information useful in better understanding carcinogensesis. Lastly, arsenic contamina (open full item for complete abstract)

Committee: Dr. Joseph Caruso (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2006, Arts and Sciences : Chemistry

Microchip capillary electrophoresis (CE) is the miniaturized form of traditional CE, a powerful electrical separation technique performed in a capillary with micron diameters. The advantages of microchip CE over traditional CE include shorter analysis time and less consumption of chemicals and reagent. The objective of the microchip program in our group is to develop microchip CE instrumentation and methodologies for high throughput screening of pharmaceuticals. As an important step, my work was focused on the development of methodologies for binding studies and trace protein assays in single-lane glass microchips. A pair of thrombin and thrombin-binding aptamer was chosen as a model system to demonstrate the feasibility of microchip CE in binding studies. The combination of a short detection length (1.0 cm) and a high electric field (670 V/cm) succeeded in the detection of the aptamer-thrombin complex and reduction of thrombin adsorption. The limit of detection (LOD) reached 5.0 nM of thrombin. To determine the equilibrium dissociation constant of aptamer-thrombin, a simple hydrodynamic injection method in microchips was developed. This hydrodynamic injection significantly reduces sample bias although the dispensing bias still exists. Using the hydrodynamic injection method, the dissociation constant of aptamer-thrombin was determined to be 23 nM which is consistent with reported results. Moreover, an accurate and fast frontal analysis method was developed for the determination of dissociation constant with a model pair of aptamer and immunoglobulin E (IgE). The capability of microchip CE coupled with a laser-induced fluorescence (LIF) detection system in the detection of trace protein was demonstrated using a 66-mer photoaptamer to detect 165-mer vascular endothelial growth factor (VEGF165). A LOD of 1.0 nM was achieved for the detection of VEGF165 using the fluorescently-labeled photoaptamer. To enhance detection sensitivity of analyte in microchip CE, a field-am (open full item for complete abstract)

Committee: Dr. William Heineman (Advisor) Subjects: Chemistry, Analytical

PhD, University of Cincinnati, 2006, Arts and Sciences : Chemistry

The unique solvation properties of ionic liquids (ILs) are being used to advantage in the dissolution of a wide range of organic and inorganic substances, including both neutral and charged species. Investigations of the physicochemical properties of ILs and solute/stationary-phase interactions in GC suggest that ILs may be useful as multimodal media in chromatographic separations. In this work, a butylimidazolium cation with a Br- counter-ion was immobilized on porous silica particles and examined as a stationary phase for LC. In chromatography, the LSER methodology has been used to correlate retention with fundamental solute/mobile-phase and solute/stationary-phase properties. The present study has established a relationship between the system constants and properties of an IL-type stationary phase by the LSER approach. It focuses on characterizing solute retention using methanol-water and acetonitrile-water binary mobile phases. Results are discussed in terms of the chemical meaning of the magnitude of the coefficient as well as its sign and the effect of mobile-phase composition. These results and further comparisons with conventional systems confirm the presence of the hydrophobic retention property and the importance of the ion-dipole/dipole-dipole retention mechanism for two stationary phases (the butylimidazolium-based and a commercial anion exchange). The impact of organic modifiers on separation of selected compounds is also discussed. In addition, the primary results of the LSER extension for modeling retentions of some ionizable compounds, as well as error propagations in retention, are presented. The preliminary application of IL-based stationary phase on polyphenol separation will be examined.

Committee: Dr. Apryll Stalcup (Advisor) Subjects: Chemistry, Analytical