Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Li, Tingyu

Committee Member

Pittman, Charles U., Jr.

Committee Member

Sygula, Andrzej

Committee Member

Henry, William P.

Committee Member

Xia, Kang

Date of Degree

8-8-2009

Original embargo terms

MSU Only Indefinitely

Document Type

Dissertation - Campus Access Only

Major

Chemistry

Degree Name

Doctor of Philosophy

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

Various innovative separation methods in chromatography have been proposed. The interaction of the 4-t-butylphenyl group with b-cyclodextrin is well-known; compounds tagged with the 4-t-butylphenyl group are separated from untagged compounds using b-cyclodextrin column. In this study, increasing the chain length of tagged molecules does not increase the retention time but depends on other functional groups present, while increasing the number of tags in a molecule increases retention time. The t-butyl group was also compared to adamantyl and lithocholic acid tags. In-house b-cyclodextrin columns were synthesized to observe the effect of the linkage of the cyclodextrin molecule to the support. Furthermore, tagged products could be separated from the starting materials using in-house columns employing flash b-cyclodextrin. Supported room temperature ionic liquids (SILs/MSILs) were explored for the extraction of polyunsaturated triacylglycerols (PUTAGs).Various room temperature ionic liquids (RTILs) with silver salts were tested for extraction effectiveness.The most hydrophobic RTIL [Hmim][PF6] in this study, with dissolved AgBF4 proved to be the best combination for effective extraction. RTILs supported on silica gel and mesoporous SBA-15 reacted with silver salts (psorbents) were synthesized and characterized. The later support revealed a conserved mesopore structure by SEM, TEM, SAXS and N2 isotherms. Trilinolenin (tri-18:3) quantification was explored by conversion to polyunsaturated fatty acid alcohols and methyl esters, Proton NMR spectroscopy and by non-aqueous reverse phase (NARP)-HPLC with evaporative light scattering detector (ELSD). Tri-18:3 and its free fatty acid (FFA-18:3) were extracted selectively and quantified using a two-step methodology. The extraction of a-tocopherol with RTILS modified with organic anions was also successfully demonstrated. Finally, studies of chiral stationary phases with on-resin cyclic oligoprolines were demonstrated. Cross linking of linear oligoprolines was shown to disrupt the poly-proline helix (II) thus leading to lower number of analytes resolved. On-resin cyclic oligoproline synthesis was successful for penta- and tetraproline but failed for the triproline. PyBOP/HOBt/DIPEA was employed for effective cyclization. The on-resin cyclic oligoproline CSP showed a lower number of resolved analytes, implying the importance of the poly-proline helix for chiral selectivity. The innovative separations in this study serve as starting points for developing mature separation methods.

URI

https://hdl.handle.net/11668/19451

Comments

separations||chiral||ionic liquids||polyunsaturated||tag||chromatography

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