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The interactive effects of humic acids (HAs) and salinity on the bioavailability and toxicity of the pesticides chlorpyrifos and 4,4'-dichlorodiphenyltrichloroethane (DDT) were investigated. The effects of various HAs on the toxicity of chlorpyrifos were initially assessed with the chronic MicrotoxRTM test. Environmentally relevant concentrations of Aldrich, Peat, Leonardite and Suwannee River HAs had no significant effect on the toxicity of either chlorpyrifos or copper (Cu), the test's positive control. as reductions in contaminant toxicity had previously been reported for some contaminants by HAs, it appeared that salinity might be a mitigating factor. Thus salinity effects were further investigated with Aldrich HA only, in freshwater and at lower salinities. HA-pesticide associations were assessed through the pesticides' relative uptake by solid-phase microextraction (SPME) in the presence of Aldrich HA. Such binding has been hypothesized to reduce contaminant bioavailability. Increasing salinity (0--20 ppt) had no effect on the uptake of DDT by SPME, but generally enhanced that of chlorpyrifos. Aldrich HA alone greatly decreased the relative uptake of both pesticides at environmentally relevant DOM concentrations (∼0--20 mg C/l), and the effect was more pronounced for DDT. Increases in salinity reduced the effects of HA on uptake by SPME, and seemed to have an "effect threshold" between 1 and 5 ppt. to examine the biological consequences of possible HA-salinity interactions, the acute toxicities of chlorpyrifos and DDT were assessed using both freshwater (Ceriodaphnia dubia) and saltwater (Americamysis bahia) crustaceans. The DDT 24 hour LC50 for C. dubia was 1050 ng/l. No definitive value was obtained for A. bahia. CPF was more acutely toxic, with LC50s of 326 ng/l for A. bahia and 78.8 ng/l for C. dubia. Results of the acute toxicity experiments were in good agreement with the SPME data; i.e. while pesticide toxicities were reduced by HAs in freshwater, no reductions were seen in saline water (20 ppt). The toxicity reduction in freshwater was proportional to the HA concentration. The difference in toxicity mitigation is believed to be a function of salinity effects on HA-pesticide binding, likely due to conformational changes in the HA molecules, rather than organismal effects.

Investigations of environmental hormone contamination commonly utilize solidphase extraction (SPE) followed by high-performance liquid chromatography / (electrospray ionization) tandem mass spectrometry (HPLC/(ESI)MS2) in the detection of estrogens. Matrix interference is widely reported. In this study, androgens were targeted alongside estrogens as environmentally co-introduced endocrine disrupting chemicals. Analytical methods were developed in parallel for detection of several hormones from each class, with comparison of protocols and instrumental parameters. Ultraperformance LC (UPLC®), an emerging technology advertised for reduced retention times, was used in place of HPLC for hormone separation. Applicability to diverse aqueous samples was tested. Matrix interference was combated with two rarely used techniques: atmospheric pressure chemical ionization (APCI) MS2 and extract purification by size exclusion chromatography (SEC). Infusion and spiking tests were performed in (ESI)MS2 and (APCI)MS2, demonstrating relative matrix disruption of hormone signals. An SEC fractionation protocol was developed and applied to extracted wastewater samples prior to UPLC/MS2 analysis. Hormone recoveries were compared to those obtained without SEC purification. In accordance with these experiments, it was found that estrogen and androgen contaminants can be simultaneously extracted using C18 SPE. This approach reduces the amount of sample, supplies, and time required in preparation for instrumental analysis. In UPLC separation, a broader gradient, slower flow rate, and increased run time were used for the androgens to counteract structural similarity and reduced polarity. The androgens were most readily detected using positive (ESI)MS2, versus negative for the estrogens, with modifier addition for signal enhancement. Electron delocalization in the estrogen and testosterone molecular structures facilitated ionization, permitting MS2 detection at or below 23 pg on-column versus 500 pg for the androgens lacking bond conjugation. Recoveries of all analytes from deionized water were 67-112% using UPLC/(ESI)MS2. Use of UPLC reduced retention times and solvent usage in comparison to HPLC, permitting adequate resolution of the hormones within 7 min in the presence of clean solvents. In environmental samples, the rapid analyses proved susceptible to matrix interference, with lack of signal resolution amidst unresolved complex mixtures. The application of (APCI)MS2 to complex samples showed promise in combating matrix interference, permitting detection of hormones spiked into wastewater that were not observed using (ESI)MS2. The ionization methods tended toward opposite matrix effects, with 140-410% recoveries (i.e. ion enhancement) from effluents using APCI and 5-120% (i.e. ion suppression) using ESI. Application of SEC prior to instrumental analysis removed some interfering compounds, allowing recoveries of 48-98% for several hormones using UPLC/(APCI)MS2.

Very selective and highly sensitive ways to detect peptides or proteins of interest remain important goals in proteomics applications. This dissertation focuses on the use of amphiphilic polymeric materials that self-assemble as reverse micelles in apolar solvents as part of a liquid-liquid extraction methodology to selectively extract and concentrate peptides from aqueous solutions. After extraction the polymer-peptide mixtures are amenable to direct analysis by mass spectrometry (MS) using matrix-assisted laser desorption/ionization (MALDI). The polymeric materials that self-assemble in apolar solvents have charged interiors that allow oppositely-charged peptides to readily migrate into the aggregate's core, while similarly-charged peptides do not. This charge complementarity can be controlled by varying aqueous phase pH such that peptides having a narrow range of a pI values can be selectively isolated. Insights into the extraction mechanism and how these materials can potentially open the way for multidimensional separations were also studied. Furthermore, amino acid-specific covalent labels are introduced inside the reverse micelles to selectively react with the extracted peptides having the amino acid of interest. This reaction leads to a mass signature that can be used to identify peptides with amino acids of interest. In addition, bulk ampholytic gels and small commercial surfactants were investigated as extraction materials. Overall, our results reveal that the amphiphilic polymeric reverse micelles are far superior for selectively and efficiently extracting peptides from complex mixtures.

The goal of current research is probing the relationship between catalyst features and the fuel cell performance with a range of in-depth structural analysis. The study investigated different catalyst systems including core-shell structured catalyst, catalysts with unique carbon-transition metal oxide supports. PtRu catalysts nanoparticles with unique core-shell structure, one of the most practical catalysts in PEMFC technology, have been successfully obtained with the evidence from the characterization results. It is found that the enhanced CO oxidation may be achieved through the interactions between the Pt shell and Ru core atoms, which can modify the electronic structure of the Pt surface by the presence of subsurface Ru atoms or by disrupting the Pt surface arrangement. Furthermore, the possibility of presence of the compressive strain within the Pt rich shell is proved by the lattice measurements, which could significantly affect the catalytic activity. Pt catalysts supported on complex oxide and carbon support were studied to investigate the relationship between the catalyst and its support. Observations from STEM images and HAADF and energy dispersive X-ray spectrometry demonstrate the preferential distribution of Pt nanoparticles on the hybrid supports, which include Nb2O3 / C, Ta2O5 / C, (Nb2O3+TiOx) / C, (Ta2O5+TiOx) / C, and (WO3+TiOx)/C). Such evidence indicates the interaction between the catalyst and support is based on the presence of an interconnected oxide network over the carbon support and the presence of Pt strongly connected to the oxide network. In addition, using electron energy loss spectroscopy (EELS), the electronic structure of the catalyst support under various conditions was also studied to provide further evidence of the strong metal support interaction effect. / Thesis / Doctor of Philosophy (PhD)

<p dir="ltr">In mass spectrometry, analyte molecules are ionized by various mechanisms, such that they can be manipulated by electric and magnetic fields. By performing such manipulations, the mass to charge (<i>m/z</i>) ratio of the analyte molecules can be measured. Many methods for ion manipulation that allow for such <i>m/z </i>determination have been developed in the form of different mass analyzers. These include but are not limited to magnetic/electric sector instruments, time-of-flight (TOF) mass analyzers, 3D quadrupole ion traps, quadrupole mass filters, linear quadrupole ion traps (LITs), Fourier-transform ion cyclotron resonance (FT-ICR) instruments, Orbitrap mass analyzers, and electrostatic linear ion traps (ELITs). Each of these mass analyzers has unique advantages and disadvantages resulting from its specific mechanism of operation, allowing each of these to find a niche in mass spectrometry applications. The ELIT is a mass analyzer composed of two opposing ion mirrors, which cause trapped high energy ions to oscillate along a linear axial trajectory. The oscillation period of ions in the ELIT is dependent on injection energy, the potential energy and electrode geometry of the ELIT, and the ion <i>m/z</i> ratio. As such, mass spectra can be measured by measuring the frequency of ion packets in the ELIT in Fourier-transform (FT) operation mode, or by or by allowing ions to separate spatially in an <i>m/z </i>dependent manner before detection via a microchannel plate (MCP) in multiple-reflection time-of-flight (MR-TOF) mode of operation. The ability to perform two orthogonal mass analysis techniques in a single mass analyzer is one key advantage of the ELIT. Both FT-MS, and MR-TOF mode of operation are high-resolution techniques, making the ELIT unique in its excellent performance characteristics despite low complexity and manufacturing cost. Additionally, the ELIT can be used to perform high-resolution ion isolations, which makes it especially attractive for tandem-MS.</p><p dir="ltr">In chapter 1, the operating principles for MR-TOF and FT-MS modes of operation in an ELIT are discussed. In chapter 2 and 3, the performance, limitations, and applications of the mirror-switching isolation technique in the ELIT are discussed. Given the high-resolution performance of the ELIT for both mass analysis and ion isolation, it is clear that the ELIT has great potential for tandem-MS applications which require high-resolution in either the precursor selection, mass analysis step, or both. In chapters 4, 5, and 6, the implementation and development of infrared multi-photon dissociation, and surface-induced dissociation techniques in the ELIT are discussed, and it is shown that the ELIT can be used to as a standalone tandem mass spectrometer. While not performed on the ELIT instrument, the charge-based valet parking technique discussed in chapter 7 applies to tandem-MS as a whole, as it is shown to improve fragment yield in ETD. Finally, in chapter 8, the future directions of development for the ELIT mass analyzer are discussed.</p>

The goal of this research has been to enhance vapor generation techniques for atomic spectrometry--particularly for atomic absorption spectrometry--through more fundamental examinations of gas-liquid separation processes, expansion of flow injection vapor generation's usefulness through the development and improvement of specific applications, and examination of how flow injection vapor generation's capabilities can be extended through gas-phase preconcentration in hydride generation and examination of generating alternative metal vapors from volatile metal chelates. Gas-liquid separation efficiency for a commercially available flow injection vapor generation apparatus was determined via mercury cold vapor generation with amalgam concentration of the mercury vapor. The efficiency obtained, combined with efficiency information obtained by other investigators of flow injection-hydride generation, demonstrated that the apparatus achieves virtually complete separation for mercury vapor and the hydride-forming elements. This highly efficient vapor generation apparatus was then used for the development of specific applications. Determinations of arsenic in highly interfering transition metal matrices, on-line decomposition of organomercury species prior to mercury cold vapor generation, and on-line pre-reduction of arsenic following species-selective pretreatment of urine samples have all been developed. The capabilities of flow injection vapor generation were also extended in this work. Peltier coolers were used to preconcentrate stibine vapor (SbH$\sb3)$ prior to detection, leading to enhanced sensitivity for antimony. Volatile metal chelates were also synthesized on-line--particularly Cu(trifluoroacetylacetone)$\sb2$--in an attempt to extend the range of elements determinable by flow injection vapor generation.

Analytical methods of separation are the focus of this dissertation. Several of the studies are of a clinical nature and concern the effects of various medication and materials additives on low birth weight infants. In all cases, the chemicals under consideration are federally approved species, but must be reevaluated because of the underdevelopment of the infants. The first study investigates butylated hydroxy toluene (BHT), a common food and drug antioxidant, which is a component of the nutrition supplement administered to children. A high performance liquid chromatographic determination for the BHT and metabolites was required. Reverse phase chromatography was employed using photodiode array detection. This allowed for post-run optimization of detection wavelengths which was critical due to the limited sample size available. Sample preparation utilized solid phase extraction methodology to reduce the biological matrix. Results which highlight the differences between adult and infant samples are given. The second study incorporates element specific detection with a microwave induced plasma for gas chromatographic analysis to determine isothiazolinones in infant blood. This feasibility study illustrates the ability of the technique to discriminate the analytes from a complex matrix. Lysing of red blood cells was found to be necessary in order to quantitatively determine the analytes at the part per billion level necessary. The final clinical study exploits the features of photodiode array detection for liquid chromatography. A chromatographic peak is shown to contain two components and the source of the contaminant has been traced to drug infusion tubing. This peak has not been positively identified but spectral and retention characteristics suggest that it is a polymeric stabilizer used in the manufacture of polyvinylchloride tubing. Next, capillary isotachophoresis is employed to separate the conformers of calmodulin, a metallo-protein which undergoes changes in its tertiary structure as it binds up to four calcium ions. In isotachophoresis analytes travel with constant velocity in an electric field. Differences in electrophoretic mobilities allow analytes to migrate into discrete zones. Conductivity detection was used in this analysis. A description of the process and instrumentation is followed by a section of troubleshooting analysis. The separation of the calmodulin conformers is shown and experimental considerations for working with this and other metallo-proteins are discussed.

An enclosed inductively coupled plasma (ICP) was designed to overcome the limitations of the conventional ICP torch for the analysis of toxic and reactive gases. In particular, the extreme toxicity of arsine prevents the safe application of a standard ICP torch and gas exhaust for the direct determination of impurities in arsine. The enclosed ICP provides containment of toxic gases in a quartz discharge container. The total volume of toxic gas consumed is minimized as well. Parameter characterization of a sealed ICP system was investigated. The choice and role of the additive gas, effect of flow rate, discharge container size and geometry, rf power, signal reproducibility, operating parameters, and procedures were determined. Modifiers were investigated to prevent deposition of arsenic and metallic impurities to the cooler container walls. The first reported direct qualitative analysis of semiconductor-grade arsine is described. Chlorine was found to be the most effective additive gas for arsenic vaporization for both flowing and static ICP operation. Chlorine addition to the argon stream extended the arsine introduction to concentrations of up to 10% into the discharge. An rf generator (40.68 MHz) power of 1.0 kW and 30% chlorine content for 7.11% arsine in a 65-mm diameter spherical container were applied to identify eight impurities qualitatively: C, Fe, Ge, Mg, Mo, Ni, Sn, and V. A vapor phase introduction system was developed to calibrate the SICP. Theoretical detection limits for tin in arsine and chlorine were calculated as 2.00 and 0.218 ppb, respectively. A hypothesis was formulated to describe the stability of the chlorine-containing arsine plasma. Proof of this hypothesis will require techniques to probe the presence and distribution of ion and atom species within the sealed discharge. The absolute noise power spectra of atomic emission signals from the SICP for flowing and static operation demonstrated that noise below 5 Hz was lower than observed in conventional ICP discharges. White noise levels were lower for the SICP than a conventional ICP. The implications of this result is the improvement in signal-to-noise ratio signal averaging techniques. This can provide very low analyte detection limits measured in the sealed inductively coupled plasma.

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