Stir bar sorptive extraction and gas chromatography : mass spectrometry for the analysis of biological matrices

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dc.contributor.advisor Sandra, P. J. F.
dc.contributor.advisor Crouch, A. M.
dc.contributor.advisor Burger, B. V. Stopforth, A.
dc.contributor.other University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. 2008-04-14T09:55:35Z en_ZA 2010-06-01T08:13:34Z 2008-04-14T09:55:35Z en_ZA 2010-06-01T08:13:34Z 2007-12
dc.description Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2007.
dc.description.abstract This study describes the development of simplified analytical methods for the analysis of trace quantities of selected naturally occurring target compounds in complex biological matrices by stir bar sorptive extraction (SBSE) and gas chromatography/mass spectrometry (GC/MS). SBSE facilitates the direct extraction of organic compounds from aqueous samples by allowing the solutes to partition between the aqueous phase and a glass stir bar that is coated with a layer of polydimethylsiloxane (PDMS). The partitioning of polar compounds into the PDMS coating was enhanced by using different derivatization techniques in combination with SBSE. The derivatization of polar functional groups was performed with ethyl chloroformate, acetic acid anhydride, and O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine directly in the aqueous samples. Headspace derivatization of compounds containing a secondary alcohol group was performed directly on the stir bar coating in the presence of acetic acid anhydride vapors. The derivatized compounds were thermally desorbed (TD) and analyzed on-line by GC/MS. A number of experimental parameters, including salt addition, temperature and time were optimized to improve the recovery of the derivatized compounds by SBSE. The optimized methods were validated in terms of linearity, precision, and detection and quantitation limits prior to performing the quantification. Trace levels of tuberculostearic acid, a marker of tuberculosis, was detected in sputum samples that were decontaminated and concentrated before being analyzed by SBSE-TD-GC/MS. The method is sufficiently sensitive to detect the marker without the need to culture the organisms, namely M. Tuberculosis. The analysis of 4-hydroxynonenal has also been demonstrated by detecting trace levels of this oxidative stress marker in urine samples obtained from healthy volunteers. Furthermore, abnormally low testosterone/epitestosterone ratios were detected in a group of HIV positive patients by means of SBSE-TD-GC/MS. Further research is required to determine the clinical significance of this finding in the context of HIV infection. Finally, the excessive urinary excretion of estrone and 17β-estradiol following the administration of a high dose of the conjugated equine estrogens to a female volunteer has also been demonstrated. en
dc.format.extent 2550740 bytes en_ZA
dc.format.mimetype application/pdf en_ZA
dc.language.iso en
dc.publisher Stellenbosch : University of Stellenbosch
dc.subject Dissertations -- Chemistry en
dc.subject Theses -- Chemistry en
dc.subject Gas chromatography en
dc.subject Mass spectrometry en
dc.subject Extraction (Chemistry) en
dc.title Stir bar sorptive extraction and gas chromatography : mass spectrometry for the analysis of biological matrices en
dc.type Thesis
dc.rights.holder University of Stellenbosch
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