Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)



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.


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


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.