Date of Award

Spring 5-15-2017

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

Wyatt R. Murphy, Ph.D

Committee Member

Cecilia Marzabadi, Ph.D

Keywords

NSAIDs using solid phase microextraction; SPME; comprehensive gas chromatography-time of flight-mass spectrometry; SPME-GCxGC-TOF-MS; water analysis, SPME-GC-MS-MS, GC-VUV

Abstract

The selectivity of a method is defined by its ability to determine a particular analyte without interference in a complex mixture. Selectivity in gas chromatography (GC) can be obtained at different points in the analysis including the sample preparation, sample introduction, separation on column and detection. In GC, the first dimension of selectivity can be obtained in sample preparation; the second dimension in chromatographic separation and the third dimension in detection. This research focuses on the relationships between selectivity in these different dimensions, studied using some non-steroidal anti-inflammatory drugs, glucocorticoids, fatty acid methyl esters and polycyclic aromatic hydrocarbons. Recent methodologies used for selective sample preparation such as supercritical fluid extraction, QuEChERs extraction and solid phase microextraction (SPME) are ‘greener’ approaches. Column selectivity is explained using comprehensive gas chromatography (GCxGC), using various column combinations. Detector selectivity is explained using new detection technologies, including multidimensional mass spectrometry (MS-MS) and vacuum ultraviolet detection (VUV), which show potential for better detection at low detection limits using MS-MS, and better separation of isomers using VUV. In method development, considering selectivity in all separation dimensions can provide the most efficient, and most sensitive method.

The goal of this work was to expand the multidimensional analysis of drugs using different extraction (SPME), separation (GCxGC-TOFMS) and detection (GC-MS-MS) technology in gas chromatographic analysis which is less explored in the pharmaceutical applications as compared to applications in fuel and natural gas industry. The research focused on separation of non-steroidal anti-inflammatory drugs (NSAIDs) in water without derivatization using SPME as extraction technique with a comprehensive two dimensional gas chromatography time of flight mass spectrometer (GCxGC-TOFMS) to separate a complex mixture. Extraction parameters such as pH, temperature, time of extraction, time of desorption were evaluated using gas chromatograph coupled with a triple quadrupole mass spectrometer (GC-MS-MS). Here, the same class of drugs, NSAIDs were separated using two mass spectrometers in series. Also to study the selectivity, an application of GCxGC on fatty acid methyl esters (FAMEs) using different column combinations were evaluated for the effect of modulation time and temperature and effect of the hot pulse. This research was extended to different applications to separate a mixture of polycyclic aromatic hydrocarbons (PAHs) to show the selectivity of extraction combined with detection, using GC-MS-MS. Another application involves a new detector technology, gas chromatography with vacuum ultraviolet detector (GC-VUV) with the use of glucocorticoids as a class of drugs and to determine the water content from the sample preparation in SPME for NSAIDs to represent unique selectivity. This detector is sensitive to water, allowing water detection using GC which has been a major limitation, and this detector is complementary to MS.

All these techniques when combined together can provide an enormous amount of information on extraction, separation and detection on a different class of analytes.

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