ORCID Identifier(s)

0000-0002-6380-6613

Graduation Semester and Year

2020

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Kevin A Schug

Second Advisor

Daniel W Armstrong

Abstract

This thesis contributes to advancing liquid and gas chromatography by introducing new stationary phases for HPLC and a new hyphenated GC technique. In the first section, new pH stable stationary phases based on geopolymers are presented for applications in liquid chromatography. The first-ever synthesis of micron-sized spherical particles of geopolymers, customized to be used as HPLC stationary phases, is reported. Complete material characterization of geopolymers using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, laser diffraction, and porosimetry is shown. The chromatographic evaluation of geopolymers is done by comparing parameters such as hydrophilicity, ion exchange selectivity, efficiency, hydrolytic stability, and pH stability with silica stationary phases. Geopolymers are successfully employed for separations of various classes of compounds using hydrophilic interaction liquid chromatography (HILIC) and normal phase chromatography. Furthermore, geopolymer monoliths are synthesized by inducing higher and interconnected porosity in their otherwise impermeable structure to advance their applications in fields like separation science, catalysis, and drug delivery. This thesis also presents chemical modifications of original geopolymer particles to extend the applications in separation and adsorption sciences. Firstly, transition metal-free geopolymer microspheres are introduced as a second-generation geopolymer stationary phase, showcasing the improvements in the chromatographic performance (particularly peak shapes). Secondly, barium exchanged geopolymers are proposed as new HILIC stationary phases specially developed for separations of compounds with acidic functional groups like carboxylates, sulfonates, and sulfates. Thirdly, iron oxide coated geopolymer microspheres are demonstrated as cost-effective and porous adsorbents for arsenate, arsenite, monomethyl arsenate, and dimethyl arsenate. The second section of this thesis introduces the concept of hyphenation of gas chromatography (GC) with molecular rotational resonance spectroscopy (GC-MRR). The power of MRR lies in its ability to discern the slightest change in the mass and/or molecular geometry in a molecule resulting in distinct rotational spectra. The unique abilities of the GC-MRR are demonstrated by the separation and quantification of a series of 24 isotopologues and isotopomers of five organic compounds. Natural isotopic abundances of mixtures of compounds containing chlorine, bromine, and sulfur heteroatoms are easily determined.

Keywords

Geopolymer, Molecular rotational resonance spectroscopy

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

Included in

Chemistry Commons

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