Graduation Semester and Year

2013

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Daniel W Armstrong

Abstract

Hydrophilic interaction chromatography (HILIC) is now considered as a viable and established analytical tool for the separation of very polar and hydrophilic compounds, which are not sufficiently retained under Reversed phase liquid chromatography (RPLC). HILIC is becoming a routine technique in the areas of proteomic and metabolomic research and it is steadily increasing in importance in the fields of pharmaceutical, biolological, environmental and food chemistry. HILIC shows a complementary selectivity to RPLC. The use of water-miscible organic rich mobile phases (generally a mixture of acetonitrile and water (1-40 % of water in the mobile phase) is compatible with atmospheric pressure mass spectrometric (MS) analysis. In this chromatographic technique, the polar analytes interact with a hydrophilic stationary phase via a combination of hydrogen bonding, dipolar interactions, electrostatic interactions and sometimes partitioning between the mobile phase and the water-rich layer that is solvating the surface of the stationary phase. There are an increasing number of HILIC stationary phases commercially available. Understanding the principles that drive the separation and selection of both stationary phase and the chromatographic conditions enhance the number and quality of the applications in the HILIC mode. In part one of this thesis, we present new approaches for the HILIC separation of very important biological compounds using a recently developed silica based native cyclofructan 6 (FRULIC-N) stationary phase. This stationary phase provided excellent selectivity towards mononucleotides. Traditional hydrogen bonding/ dipolar interactions can be supplemented by dynamic ion interaction effects for the separation of these anionic analytes. Also, we present the development of new HILIC stationary phase based on sulfonated cyclofructan 6, and its applications. The new columns successfully separates polar and hydrophilic compounds including beta blockers, xanthines, salicylic acid related compounds, nucleic acid bases, nucleosides, maltooligosaccharides, water soluble vitamins and amino acids. Today, chirality is an important concern for biological processes because asymmetry dominates biological processes. Chirality is of fundamental interest in large number of areas including chemistry, biochemistry, pharmacology and so forth. In particular, the separation and characterization of the desired enantiomer in active pharmaceutical ingredients is critical in drug discovery and development. High performance liquid chromatography (HPLC) is ubiquitous as a highly efficient and selective technique in enantiomeric separation and analysis. However, the efficient development of enantiomeric separation methods is still challenging and time consuming. In part two of this thesis, we present the development of new chiral stationary phases (CSPs) based on cyclofructans; evaluation and applications of these newly synthesized CSPs. The isopropyl-functionalized cyclofructan 6 chiral stationary phases (LARIHC CF6-P) provided remarkable enantiomeric selectivity for the primary amines while R-naphthylethyl-carbamate cyclofructan 6 (LARIHC CF6-RN) and dimethylphenyl-carbamate cyclofructan 7 (LARIHC CF7-DMP provided enantioselectivity toward a broad range of compounds, including chiral acids, amines, metal complexes, and neutral compounds. Also, we present new classes of chiral selectors based on cationic and basic derivatives of cyclofructan 6 for the first time as bonded chiral stationary phases for high performance liquid chromatography (HPLC). Cyclofructans, cyclic fructofuranose oligomers, have unique crown ether cores. They tend to form complexes with a variety of metal cations in solution. This special character of cyclofructans prompted NMR studies in order to understand the selective complexation ability of CFs for metal cations. In the last part of this thesis, we examine the host-guest complexation between cyclofructans and large numbers of metal ions. This study showed the specific binding ability of native CF6 with Ba2+ and Pb2+ cations, while the traditional synthetic crown ether form preferential complexes with the alkali metal ions.

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

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