My dissertation primarily focuses on the fabrication of materials for solid phase microextraction (SPME) and separation devices. In my first project, I used direct current magnetron sputtering (DCMS) to prepare sputtered silicon coatings on fused silica fibers. These fibers were then subjected to the chemical vapor deposition of 6-phenyhexylsilane (6-PH) as a stationary phase. Six different types of fibers were made using two different throw distances (4 cm and 20 cm) and three different silicon thicknesses (0.5, 1.8, and 2.8 µm). These coatings were characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), spectroscopic ellipsometry (SE), and contact angle goniometry. These SPME fibers were evaluated using gas chromatography (GC). The extraction efficiencies of sputtered, 6-PH-coated fibers were compared to that of a commercial fiber (7 µm PDMS) for polycyclic aromatic hydrocarbons (PAHs). Our 2.8 µm thick sputtered silicon coatings showed competitive extraction of low molecular weight PAHs and ca. 3 times the extraction efficiency for higher molecular weight PAHs. In addition, it outperformed the commercial fiber by showing better linearity, repeatability, and detection limits. A method for analyzing polyaromatic hydrocarbons in baby formula was developed, which showed very good linearity (0.5-125 ppb), repeatability (2-26%), detection limits (0.12-0.81 ppb), and recoveries (103-135%). In my second project, I focused on preparing sputtered carbon SPME fibers using DCMS sputtering. These fibers were tested with and without PDMS coatings on top by SPME-GC-MS. In addition, a new SPME evaluation mix was developed for testing the newly developed SPME fibers. The evaluation mix included analytes with diverse functionalities and properties. Our best carbon fiber showed very competitive extraction capabilities on a per volume basis when compared with a commercial 95 µm carbon-based fiber. In a third project, I built an ALD system to deposit thin films inside GC capillary columns. This system has a unique design that also allows for ALD on witness silicon samples before and after the capillary column. This system yields very promising results with ALD of alumina inside 5 and 12 m long capillary columns. The ALD coatings deposited inside the columns were characterized by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The thicknesses of the coatings on witness shards were almost identical to the thicknesses of the coatings in the capillaries. My fourth project focused on characterizing a liquid polymer (diphenyl siloxane dimethyl siloxane (DPS-DMS)) via SE. This material was a potential stationary phase for our SPME fibers. Transmission measurements were obtained via a dual cuvette approach that eliminated the effects of the cuvettes and their interfaces. The optical function of this material was modeled with a Sellmeier function in its transparent region.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-10765 |
| Date | 03 December 2021 |
| Creators | Patel, Dhananjay I. |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | https://lib.byu.edu/about/copyright/ |
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