Graduation Year

2017

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

Degree Granting Department

College of Arts and Sciences

Major Professor

Abdul Malik, Ph.D.

Committee Member

Theresa Evans-Nguyen, Ph.D.

Committee Member

Wayne Guida, Ph.D.

Committee Member

Rudy Schlaf, Ph.D.

Keywords

Sol-GelCoatings, Germania, Tantala, CME, SPME, In-Tube SPME, High-Performance Liquid Chromatography, pH Stability

Abstract

Microextraction is a preconcentration technique where the volume of the extracting phase is relatively small compared to the sample volume and where the extraction of analytes is non- exhaustive. One such technique is capillary microextraction where a sol-gel coating serves as the extracting phase. Sol-gel coated capillaries provide superior chemical stability in part due to highly stable surface-bonded coatings located within the fused silica capillaries that have protection from the outer polyimide layer. In this research, sol-gel sorbents developed on the inner surface of the fused-silica capillary provide thermal and solvent stability and can be effectively coupled to on-line hyphenation with HPLC. Sol-gel sorbents in this research were synthesized by employing germania- and tantala-based precursors. The newly developed sol-gel sorbents were utilized to isolate and enrich a variety of analytes from aqueous samples. Particularly, project 1 an organic-inorganic hybrid sorbent was synthesized using a sol-gel germania-based precursor and polymer hydroxyl-terminated poly-THF which provided the solvent stability required for effective on-line hyphenation of capillary microextraction (CME) with HPLC. Low run-to-run (0.19–5.96%), low capillary-to-capillary peak area RSD (0.30–8.7%) values, and low detection limits for a variety of analytes, ranging from polar to nonpolar, were obtained consistently. Sol-gel germania poly-THF coated capillaries for CME-HPLC UV analysis demonstrated stability in low and high pH environments. In project 2, an organic- inorganic hybrid sorbent based on sol-gel tantala polypropylene glycol methacrylate (PPGM) material was developed for isolating and enriching a variety of analytes (polycyclic aromatic hydrocarbons, a ketone, an alcohol, an amine, a nucleoside and nucleotide) from aqueous samples for HPLC-PAD) analysis. These analytes were selected from various chemical classes and included polycyclic aromatic hydrocarbons, a ketone, an alcohol, an amine, a nucleoside and nucleotide. This sol-gel hybrid microextraction coating provided efficient extraction with detection limits ranging from 4.41to 28.19 pM. The sol-gel tantala-based sorbent also exhibited excellent pH stability ranging from 1.0 m HCl and 1.0 M NaOH. Furthermore, the sol-gel sorbent proved capable of withstanding thermal condition up to 300 °C. RSD values of run-to-run in evaluating repeatability of CME on the sol-gel tantala-based sorbent demonstrated great reproducibility with a range of 0.23% to 3.83%, while capillary-to-capillary RSD values reflecting capillary preparation method reproducibility ranged from 0.24% to 4.11%. In project 3, the incorporation of ionic liquid (1-butyl-4-methylpyridinium (tetrafluoroborate)) in a novel hybrid sol-gel tantala-silica extraction medium generated a porous morphology, which increased the available surface and provided better extraction performance. Extraction on the sol-gel tantala-PPGM sorbent was compared with three other sorbents, which were developed by addition of (1) ionic liquid, (2) a sol-gel co-precursor ((3-aminopropyl) trimethoxysilane), and (3) a sol-gel co-precursor and IL. Results showed that the sol-gel tantala-PPGM sorbent with the incorporation of both IL and a sol-gel co-precursor provided the highest extraction capacity for the selected analytes. The hybrid sol-gel tantala-PPGM sorbent coating with IL yielded high extraction efficiency and low detection limit for selected analytes (ranging from 5.05 pM to 5.65 x 101 pM). HPLC peak area RSD values for run-to-run and capillary-to-capillary were obtained under 5% for all sol-gel sorbents.

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