The design of any supercritical fluid extraction (SFE) experiment should break down into two parts: 1) removal of the analytes of interest from the bulk matrix and 2) deposition of those analytes in a user friendly manner for further studies (spectroscopy or chromatography). While great attention has been paid to the extraction of analytes, less attention has been paid for their efficient collection after extraction. Currently solid phase trapping and liquid trapping are available for off-line collection of analytes after SFE. A polarity test mix consisting of acetophenone, <i>N,N</i>-dimethylaniline, naphthalene, <i>n</i>-decanoic acid, 2-naphthol, and <i>n</i>-tetracosane was spiked onto sand and extracted with supercritical carbon dioxide to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvents and four mixed collection solvent systems were studied. When one-component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes were possible. Additional studies were performed with carbon dioxide modified with 1, or 4% acetonitrile or 1, 4, or 8% methanol or toluene. With these extraction fluids, quantitative collection of the analytes with a mixed collection solvent was not possible, but excellent collection efficiencies were observed for hexane and methanol collection. / Master of Science

The supercritical fluid extraction (SFE) of twenty one polychlorinated biphenyls (PCBs) and eight organochlorine pesticides (OCPs) from freeze dried mussel tissue is discussed, demonstrated, and compared to traditional Soxhlet extractions. The aim of this study was to determine the efficacy of SFE for the extraction of these lipophilic compounds which involved a spike study to determine the feasibility of on-line sample clean-up by an inclusion of activated alumina within the extraction vessel. These spike extractions from an inert matrix showed that the chemical integrity of the PCBs was not compromised while some OCPs of the DDT derivative were decomposed to other forms. Preliminary extractions of freeze dried mussel tissue focused on the effect of static extraction time and CO₂ density on recovery of twenty three specific congeners of PCBs. These extractions of freeze dried mussel tissue showed longer static extraction time and higher density/lower temperature would yield quantitative recoveries of PCBs. Triplicate extractions of mussel tissue at the appropriate extraction parameters produced quantitative and similar recoveries to Soxhlet. Finally, an alternative supercritical fluid (CHF₃) yielded non-quantitative recoveries for PCBs and OCPs, but the use of this fluid eliminated the need to use in situ alumina to retain co-extracted lipids from the matrix. / Master of Science

The thesis outlines an investigative study of the supercritical fluid extraction (SFE) of organic natural products from two Meliaceae species. Extractions from ground wood, bark and seeds of the selected species were studied. Qualitative and quantitative studies were performed using a number of techniques. In the qualitative study, both off-line and on-line combination of micro-SFE with capillary gas chromatography (SFE-GC) were performed on the wood and bark of Cedrela toona to show the applicability of the technique in the analysis of semi-volatile components from plant matrices. Results for the on-line and off-line SFE-GC were comparable and indicated that the on-line studies could be used to predict results obtainable from large scale SFE. Dynamic SFE of the limonoid (cedrelone) from the wood of Cedrela toona using pure and modified carbon dioxide was studied on the basis of a theoretically-derived dynamic extraction model. Extracts were collected for different lengths of time in order to investigate the extraction kinetics of this compound. The theoretically-derived model which involved extrapolating data obtained from shorter extraction times was used to estimate the amount of the compound present in the wood. The estimated quantitative results were found to be comparable to exhaustive extractions using liquid hexane as well as methanol-modified carbon dioxide. Further, data from the SFE extractions were fitted into the model to produce a characteristic kinetic curve from which factors controlling the extraction of the specific compound could be predicted. Following the dynamic extraction study, a statistical optimisation strategy was used to propose a model equation for the extraction of cedrelone from the wood of Cedrela toona. As the preliminary step, a screening design utilising a two level, three-factor full factorial analysis was used to study the effects of the variables pressure, temperature and the length of extraction time on the yields of cedrelone from the wood of Cedrela toona. By a statistical analysis of variance (ANOVA) at the 95% confidence level on the preliminary data collected, pressure and temperature were found to be the significant variables influencing the yields of the compound. Finally response surface methodology using the central composite design was used in an attempt to determine the maximum response space for the pressure and temperature effects by plotting a 3-dimensional response surface graph. An ANOVA study at the 99% confidence level was then employed to establish the true model equation for the extraction. / Thesis (M.Sc.)-University of Natal, 1995.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 167-170). Also available via the Internet.

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Thesis (Ph.D.)--University of Tulsa, 1995. / Includes bibliographical references (leaves 197-214).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 156-157). Also available via the Internet.

Thesis (M.S.)--Villanova University, 2008. / Chemistry Dept. Includes bibliographical references.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 71-74). Also available in electronic format on the Internet.