ORCID Identifier(s)

ORCID 0000-0002-8583-5052

Graduation Semester and Year

Summer 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Kevin Schug

Second Advisor

Daniel Armstrong

Third Advisor

Saiful Chowdhury

Fourth Advisor

Junha Jeon

Abstract

Vacuum-assisted headspace solid-phase microextraction (Vac-HS-SPME) is a method used to increase solid-phase microextraction sampling of semi-volatile organic compounds. Three studies were conducted using Vac-HS-SPME via gas chromatography - mass spectrometry (GC-MS) methods for analysis of various sample types. First, a study was performed using Vac- HS-SPME combined with a high-capacity (HC) SPME Arrow to determine the operational fundamentals and workflow necessary to achieve optimal extraction of semi-volatile compounds from a model solid matrix (Ottawa sand). The fundamentals investigated included the seals necessary to create a leak-free sampling vial under vacuum conditions; the magnitude of the vacuum exerted, and the time needed to initiate the vacuum-assisted kinetics; and the order of sample vial preparation. Results for sample vial preparation methods demonstrated an ideal workflow requires the solid sample to be spiked before sealing the vial, rest the sample overnight, then apply vacuum to the rested sample at a pressure of -677 mbar (out of -789 mbar maximum possible vacuum with the compressor used), applied on the vial for 90 seconds.

Second, an application study was conducted using Vac-HS-HC-SPME coupled with GC- MS to compare the volatile and semi-volatile compounds of five psilocybin mushrooms (Psilocybe cubensis), along with three non-psilocybin mushroom species. Using an untargeted approach, the common volatiles detected included acids, alcohols, aldehydes, ketones, and hydrocarbons. Vac-HS-HC-SPME and HS-HC-SPME were initially compared providing 2 times increase in compound response as well as the extraction of 8 additional compounds undetected by HS-HC-SPME. The compounds unique to psilocybin mushrooms included 2-methylbutanal, valeraldehyde, benzaldehyde, 3-octen-2-one, 2-methyl-dodecane, and 2-butyl-2-octenal. The compounds unique to non-psilocybin mushrooms consisted of 2-methyl-pyrazine, 2,3- butanediol, butyric acid, butyrolactone, benzyl alcohol, 2-pyrrolidinone, and estragole. The commonly shared mushroom alcohol, 1-octen-3-ol, was determined to have a higher compound response among the psilocybin mushroom species.

Finally, a third study was conducted to develop a novel Vac-HS-HC-SPME method to derivatize in-situ fatty acids into fatty acid methyl esters from the headspace of olive oil using sulfonated poly(divinylbenzene) microspheres. The application of Vac-HS-HC-SPME combined with in-situ derivatization could potentially provide a simpler and greener method for the derivatization of oils.

Keywords

Vacuum-assisted headspace solid-phase microextraction, gas chromatography, mass spectrometry, in-situ derivatization, high-capacity SPME Arrow

Disciplines

Analytical Chemistry

Comments

I would like to thank my research advisor, Dr. Kevin Schug, for piquing my interest in analytical chemistry. He connected me with Restek Corporation for funding as a research assistant and for internships. He was patient and encouraging during the research and writing process. There are so many possibilities available to me with the support of Dr. Schug. I would also like to give thanks to everyone in the Schug group. Everyone was there to support each other and to provide any insights and assistance as needed, of which, I am truly grateful.

I would also like to thank each of my committee members, Dr. Daniel Armstrong, Dr. Saiful Chowdhury, and Dr. Junha Jeon, for their advice and encouragement. I would like to express my gratitude to Restek Corporation for financial support throughout the course of my research, to Colton Myers for continued guidance and support, to Jason Herrington for his encouragement and support, and to the Restek family for welcoming me into the fold during my two internships. It was truly an unforgettable experience. I would also like to thank Prof. Elefteria Psillakis and ExtraTech Analytical Solutions SMPC for the provision and permission of use of the metal insert to seal the sampling vials.

Finally, I would like to give my appreciation to my family. To my husband, Samuel Thomas, for his support, encouragement, and love. To my children, Zackry, Warner, and Gilbert, for understanding the sacrifice and stepping up with chores without complaint. I am blessed to have such a loving family.

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