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The technique of extraction with supercritical carbon dioxide (SC-CO$ sb2$), which is now used routinely for the recovery of non-polar analytes from a variety of liquid and semipermeable solid media, was extended to the efficient extraction of metal ions. Measurements of the solubilities in SC-CO$ sb2$ corroborated the hypothesis that the non-polar character of a series of tetraalkylammoniun dialkyldithiocarbamates ion pairs was influenced (i) primarily by the chain length of the alkyl substituent(s) on the carbamate nitrogen and (ii) to a lesser extent, by the chain length of the alkyl substituent(s) on the ammonium counter ion. In operation, analyte metal(s) in aqueous medium was derivatized by in situ complexation with the dithiocarbamate complexing reagent and the product complex(es) was partitioned into the SC-CO$ sb2$ mobile phase then purged from the extractor by replacing the headspace with fresh solvent. A novel silica flame-in-tube interface was developed for the sensitive detection, by atomic absorption spectrometry (AAS), of As, Cd, Cu, Mn, Pb, Se, or Zn in SC-CO$ sb2$ extractor eluate. For different analyte elements, the limits of detection (LODs) ranged from sub-nanogram to low picogram if standard was flow injected into the mobile phase. These sensitivities permitted differences in the rates of mobilization of different forms of the analyte metal from various media to be explored as a technique for probing the interaction of the analyte metal with the matrix. A portion of the Zn burden in fresh bovine liver was mobilized rapidly in the absence of complexing agent and the remainder was solubilized more rapidly than the Zn in a freeze-dried reference material of this tissue. The nebulizer assembly of a conventional flame-AAS was modified to extend the range of metals amenable to on-line detection. Supplemental heating of the inlet air to 200$ sp circ$C resulted in an on line detector which provided approximately a ten-fold improvement over convention

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The demand for a new solvent to treat oilsands was behind the purpose of this project; molecular dynamics simulation was used in this study. Supercritical water, supercritical carbon dioxide and other selected organic solvents in their supercritical state were studied. Meso-tetraphenyl porphyrin (H2TPP) and Octaethyl porphyrin (H2OEP) are the porphyrin model compounds and, 4-Bis-(2-pyren-1-yl-ethyl)-[2, 2] bipyridinyl (PBP) is the asphaltene model compound. A solubility parameter approach was used to infer the solubility of model compounds in the supercritical fluids. First, the solubility of water, carbon dioxide, 4 selected organic solvents, and the three model compounds were computed using molecular dynamics simulation and compared with experimental results. The computed solubility parameters showed that the model compounds would dissolve in supercritical water (22.5 MPa and 645-655 K) but exhibited no solubility in supercritical carbon dioxide. / Chemical Engineering

Thesis (Ph. D.)--Auburn University, 2005. / Abstract. Vita. "The following publications were a product of this dissertation: P.W. Bell, A.J. Thote, Y. Park, R.B. Gupta, and C.B. Roberts, "Supercritical Fluid Solvent Effects On Carboxylic Acid Dimer Formation," Proceedings of the 6th International Symposium on Supercritical Fluids, Versailles, France, paper no. PTp14, 2003 P.W. Bell, A.J. Thote, Y. Park, R.B. Gupta, and C.B. Roberts, "Strong Lewis Acid- Lewis Base Interactions between Supercritical Carbon Dioxide and Carboxylic Acids: Effects on Self-Association," Industrial & Engineering Chemistry Research, (2003), 42(25), 6280-6289 P.W. Bell, A.P. Stephens, C.B. Roberts, and S. Duke, "High-Resolution Imaging of the Supercritical Antisolvent Process," Experiments in Fluids, (2005), 38(6), 708-719 P.W. Bell, M. Anand, Fan, X., R.M. Enick, and C.B. Roberts, "Stable Suspensions of Silver Nanoparticles in Carbon Dioxide without Use of Fluorinated Compounds", Langmuir, released on web."--P. ix. Includes bibliographical references (leaves 186-197).

Thesis (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 17, 2008). Includes bibliographical references (p. 206-215).

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 193-199).