A molecular hydrogen laser, with an output of 7.8 eV photons in the vacuum ultraviolet, is evaluated as a selective source for photoionization mass spectrometry. Types of compounds ionized by the laser include a variety of amines, nitrogen heterocycles, drugs of abuse, pharmaceuticals, and polynuclear aromatic hydrocarbons (PAHS). The laser is coupled to a time-of-flight mass analyzer, which allows a spectrum to be recorded with each laser pulse. The laser is a "soft" ionization source and mass spectra of nearly all of the compounds studied yield single ion peaks due to the parent molecule with no fragments. This results in simplified mass spectra with a one-to-one correspondence of photoactive molecules with molecular ion peaks. Since the photoionization threshold of the laser is relatively low, selectivity of the photoactive species is high in the presence of a complex sample matrix. The performance of the laser source is improved with a few changes in the original design. In addition, the previous method of recording mass spectra with a photographic emulsion is replaced with a digital oscilloscope, which averages spectra over many laser pulses. As a result, a true assessment of the technique's sensitivity is finally achieved. The time-of-flight mass spectrometer is modified with a new microchannel plate ion detector and preamplifier. As a result, detection limits for PAH's improve by nearly three orders of magnitude, from the 100 ng range to the 100 pg range. Selectivity of the laser photoionization source in complex mixture analysis is demonstrated with the ability to detect PAH's in a drinking water sample at concentrations below 100 parts-per-trillion, using a simple solid-phase extraction technique. Application of the technique for rapid screening of drugs of abuse in urine is demonstrated where solid-phase extraction columns are utilized for sample pretreatment. Urine samples spiked with drugs such as cocaine, codeine, morphine, phencyclidine, and methadone, yield photoionization mass spectra consisting of parent molecular ions for the drugs with a few noninterfering ion signals from the matrix. The technique is evaluated and compared to other drug screening techniques such as enzyme-multiplied immunoassay.

The overall goal of this research is to characterize the solvent and electrolyte structure of the nonaqueous electrochemical double layer in the isomers of butanol on Ag and Au electrodes. Electrochemical and spectroscopic methods are employed to obtain structural information about the interface. In order to gain a better understanding of the Raman vibrational assignments of these alcohols, the Raman vibrational assignments were determined for a series of n-alcohols (n = 3-6, 8, 12, 14, and 18) in the spectral region from 700 to 1320 cm⁻¹ and 2800 to 3000 cm⁻¹. Solvent structure of the butanol isomers, 1-butanol, 2-butanol, and iso-butanol, were determined in-situ on rough Ag and Au electrodes using surface enhanced Raman scattering. Surface Raman selection rules were used to determine the average molecular orientation of these solvents at the electrode under potential control. The electrolyte structure in the nonaqueous electrochemical double layer has been determined using surface enhanced Raman scattering and differential capacitance measurements. Surface enhanced Raman scattering studies of the electrolyte structure were focused on probing the molecules solvating the cation and anion species, namely the alcohol and water impurity species. The ν(O-H) bands from these solvation species were monitored in these nonaqueous systems under potential control. These ν(O-H) bands distinctly describe the behavior of the LiClO₄, LiCl, LiBr, and LiI at the electrode under potential control. Differential capacitance measurements using an AC impedance method were performed to quantify anion coverages at smooth Ag electrodes in the butanol isomers. Cl⁻ and Br⁻ coverages were determined in the butanol isomers. This technique, coupled with SERS, provides complementary information about the electrolyte structure at the nonaqueous electrochemical double layer. The solvent and electrolyte structure is also determined ex-situ on emersed rough and smooth Ag and Au electrodes using Raman spectroscopy. Upon emersion of the electrodes into an inert Ar environment, solvent orientation and electrolyte behavior are investigated using Raman spectroscopy. These studies demonstrate both the utility of using Raman spectroscopy to probe emersed electrodes and the validity of emersing the electrode while preserving the double layer structure.

Call number: LD2668 .T4 1957 S57 / Master of Science

The set of molecules cucurbit[n]uril (Qn) are macrocycles composed of n glycoluril monomers linked by methylene groups. These molecules have two oxygen-ringed portals of a diameter slightly smaller than their internal cavity diameter. This thesis describes syntheses, crystallisations, crystal structure determinations, crystal packing analyses and force field calculations exploring the supramolecular chemistry of Qn molecules and their derivatives. Qn acts as a host for guest molecules and at the outset of this project no metal containing molecule had been encapsulated in a Qn molecule. One aim of this project was to prepare such complexes. This was achieved with the synthesis and characterisation of crystalline {[cis-SnCl4(H2O)2]@Q7}2(SnCl6)3(H3O)6(H2O)23. Other compounds prepared and characterised crystallographically in the course of this project are: [(Q6)(Na3(H2O)8)]2[CoCl4]4[Co(H2O)6]2[CoCl(H2O)5]2(Cl)4, (Q5@Q10)(CH3COOH)(Cl)2(H3O)2(H2O)26, (Cl@Q5)4Q6(SnCl6)8(H3O)20(H2O)24, (Q8)3(PtCl6)4(H3O)8(H2O)x, (Q8)2(PtCl6)3(H3O)6(H2O)18, (Q7)(Cr3O10)(H3O)2(H2O)x and (Q6)(SnCl6)(H3O)2(H2O)x. While the smaller Qn (n = 5?) retain their circular forms, the larger Qn (n &gt 8) are less rigid and distort to accommodate larger guests. After analysis of the crystal structures of these Qn compounds and those listed in the Cambridge Structural Database, the principal packing motifs of the Qn molecules were elucidated. The most common is the portal-to-side interaction in which the portal oxygen atoms of one Qn approach the hydrogen atoms around the equator of another Qn. Force-field calculations on guest@Qn complexes were conducted to determine the mechanism for the formation of these complexes. A comparison of the intermolecular interactions of phenylated systems and comparable fluorinated phenyl systems was made using both crystal packing analyses and forcefield energy calculations. Intermolecular energy parameters for these calculations were derived and validated in this work. The principal fluorinated species studied was the [B(C6F5)4]?anion. Examination of its crystal structures found that the substitution of the hydrogen atoms by fluorine atoms is influential enough to alter the predominant intramolecular conformation. It is the ???flipper?conformer, between pairs of perfluorophenyl groups, that is overwhelmingly the favoured conformation and this has a strong effect on the types of phenyl embraces that a [B(C6F5)4]?anion will form. While the parallel 4PFE, the offset parallel 4PFE and the orthogonal 4PFE are all observed the 6PFE is not.

M.S. / Environmental Science / A technique to measure arsenobetaine and arsenocholine in fish tissue by fast atom bombardment mass spectrometry was developed with particular attention to quantitative analysis. Experiments were performed which demonstrate analysis of the compounds desorbed directly from thin layer silica chromatography matrices, quantitative analysis of arsenobetaine in real fish samples, and accurate mass measurement of arsenobetaine in normal FAB/MS using peaks from the glycerol matrix as mass references. Improvements to the technique to quantitatively measure these important arsenic metabolites are suggested including optimization of the extraction/isolation procedures and use of isotopically labelled internal standards or surrogates for more accurate measurements.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 472-488). Also available on the Internet.

Thesis (Ph. D.)--Miami University, Dept. of Chemistry and Biochemistry, 2003. / Title from first page of PDF document. Document formatted into pages; contains xvi, 254 p. : ill. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 472-488). Also available on the Internet.

Thesis (M. Sc.)--University of Hong Kong, 1954. / References: p.72-75. Type-written copy.

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