Date of Award

Spring 5-16-2015

Degree Type

Dissertation

Degree Name

PhD. Chemistry

Department

Chemistry and Biochemistry

Advisor

Nicholas H. Snow, Ph.D

Committee Member

Yuri V. Kazakevich, Ph.D

Committee Member

Sergiu M. Gorun, Ph.D

Keywords

QuEChERS, Gas Chromatography Mass Spectrometry, GC/MS, QuEChERS-GC, Extraction, Drugs of Abuse

Abstract

QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) is an extraction technique developed by Anastassiades and co-workers initially for the extraction of veterinary drugs from animal tissue. Since its inception, it was discovered that this method is particularly adept for the extraction of polar and basic compounds, thus the majority of research previously performed using QuEChERS involves the extraction of pesticides from various matrices, especially fruits, vegetables, and other food products. Combining a liquid-liquid extraction (LLE) and a dispersive solid phase extraction (d-SPE) clean up, QuEChERS provides a clean sample for analysis by gas chromatography (GC) or liquid chromatography (LC) and is commonly used for samples with complex matrices.

The goal of this work was to expand the research that has been previously performed using QuEChERS, particularly in the area of GC analysis by exploring both the fundamental chemistry involved in the method as well as expanding its applications. The first original portion of the research performed involved investigating the chemistry in QuEChERS using a model study, the extraction of caffeine from tea. QuEChERS parameters have been optimized in the past but those optimized parameters have yet to be studied in depth to provide a deeper understanding of the chemistry involved in both the LLE and d-SPE portions of the method.

Study parameters such as pH, salt amount and type, solvent amount and type, temperature, extraction kinetics, and the partition coefficient of the final optimized method were evaluated. The findings from studying these parameters were then applied to several original applications performed during the entirety of this research, including the extraction of glucocorticoids from water and herbal medicinal products using gas chromatography triple quadrupole mass spectrometry (GC-MS/MS) and high performance liquid chromatography (HPLC), the extraction of hormones from water using GC-MS/MS and GCxGC-TOFMS including a comparison of QuEChERS to solid phase microextraction (SPME) using GC-MS/MS, and finally the extraction of drugs of abuse from synthetic urine.

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