This dissertation investigates three major problems in IC, ranging from the practical to the theoretical. The first is of interest to the field of quantitative analysis. Since ion chromatography is primarily a quantitative technique, the linear range of the detector is of particular interest. The linear range was determined to be nearly five orders of magnitude for several common ions. The probes used were fluoride, chloride, sulfate, sodium, and potassium with concentrations ranging from 10 ppb to 1000 ppm. This portion of the dissertation describes the first attempt made to elucidate the linear detection range in ion chromatography using micro-membrane suppression. The Iinearity experiments demonstrate the versatility of ion chromatography with respect to quantifiable concentrations. However, a major problem is encountered when attempting to determine a trace ion concentration in the presence of a high concentration of a similarly charged ion (matrix ion). The second part of this dissertation offers a solution to this problem. In ion chromatography, the large excess of a matrix ion affects not only the ions expected in that region of the chromatogram, but also destroys the chromatographic exchange process. One objective of this study was to develop a rapid quantitative method to determine 5 ppm chloride in the presence of 100,000 ppm sulfate. A standard anion exchange column will completely lose resolution between chloride and sulfate at a sulfate concentration of approximately 2500 ppm. The apparatus designed and built by the author uses two analytical ion—exchange columns coupled in series by a high pressure switching valve. ln order to complete the system, the author designed and built y a high pressure conductivity detector cell to monitor the conductivity of the effluent from the first column. The system works by overloading the first column and then allowing the effluent to pass onto the second column. When the trace chloride in on the second column, the first column is switched out of line. This process allows the trace chloride to be separated from the residual sulfate. The column switching study brought to light several theoretical questions about the inner workings of the packing materials used in ion chromatography. These questions include the effects that flow rate and temperature have on capacity and efficiency in ion chromatography separations. Using chloride and sulfate as probes, the chromatographic efficiency was shown to decrease from 30° to 60° C. Even more surprising was the result that sulfate retention increased with increasing temperature while chloride retention decreased under the same conditions. Detailed studies as well as possible explanations are included in the third part of this dissertation. / Ph. D.

Means of achieving rapid, efficient separations of analytes are explored in detail, with particular emphasis on the use of chromatographic and electrophoretic theory as an aid in system design and optimization. The benefits of miniaturization of chromatographic systems are assessed. First, the utility of semi-micro Ion Chromatography is explored by the manufacture of 2mm ID analytical and suppressor columns and a micro-conductivity cell. The quality of the columns and detector cell are evaluated by the separation of a test mixture and the calculation of peak variance contribution of the detector cell. The use of readily available analytical scale instrumentation for semi-micro IC is demonstrated. Next, a further downsizing of the IC system is described, in which 530μm ID fused silica tubing is utilized for column manufacture. In this case, a suppressor column is not used and UV detection is employed in the analysis of nucleoside monophosphates. Again, column performance characteristics are measured and noted. Application of this system to the separation of a hydrolysed nucleic acid sample demonstrates the feasibility of the technique to the analysis of volume-limited samples in low concentration with notable sensitivity. The benefits of a miniaturized liquid chromatographic system under pressure-driven flow is studied and the improved permeability of micropacked capillary columns is exploited in the manufacture of several 25 to 30cm columns which achieve high efficiencies with relatively low pressure drops. Van Deemter plots illustrate the performance characteristics of the columns. Finally, electroosmotic flow is studied as the motive force for liquid chromatographic separations. This combination of two techniques, packed capillary liquid chromatography and capillary electrophoresis, results in a system which achieves good resolving power through maximization of selectivity and efficiency. / Ph. D.

The advantages and disadvantages of packed capillary columns for high performance liquid chromatography are examined. Historically, the advantages are smaller sample and phase consumption, enhancement in sensitivity, easy column synthesis, higher obtainable efficiency, and easier interfacing to other techniques. These points are explored through experiments in microbore ion chromatography, packed fused silica columns, and capillary zone electrophoresis. These studies also address the disadvantages of microscale HPLC which are stringent instrument design, brittle or weak columns, poor column stability, and the lack of commercial instrumentation. The results of these investigations indicate the following. First, the purported sensitivity enhancement is really attributable to solute focusing and not to column miniaturization. Second, column synthesis is still a difficult procedure that requires experience. Third, higher efficiencies are realized, especially when the column diameter to particle diameter ratio is optimized. Fourth, interfacing to other techniques is simplified because of the lower volumetric flow rates. Finally, the only real disadvantages are stringent instrument design and brittle columns in some instances. This thesis offers means for circumventing these difficulties. / Ph. D.

No / A microemulsion electrokinetic chromatography (MEEKC) method has been developed and validated for the determination of 4-hydroxybenzoates and their impurities. These materials are commonly known as parabens and are widely used as preservatives in foods, cosmetics and pharmaceuticals. The method was shown to be selective and quantitative for the methyl, ethyl, propyl and butyl esters of 4-hydroxybenzoic acid. An internal standard, 4-hydroxyacetophenone, was employed to improve injection precision and detector linearity. In addition, 4-hydroxybenzoic acid, the major degradent, could also be monitored at the 0.1% (m/m) level. The method was successfully validated for assay and detection of the impurities in 4-hydroxybenzoic acid methyl ester and 4-hydroxybenzoic acid propyl ester samples and for the determination of 4-hydroxybenzoic acid methyl ester in a liquid pharmaceutical formulation. The determination of paraben content by MEEKC in a liquid sample was consistent with HPLC analysis. This work is the first reported validated MEEKC method and shows that the methodology can be successfully implemented into routine quality control testing.

No / The first report of the formation of an acetyl disulfide sialoside during the synthesis of thioglycosides is described. This compound is a by-product in the synthesis of the 2-thioacetyl sialoside commonly used in thioglycoside preparation. Our investigations into the identification of this novel disulfide are described.

No / RATIONALE: 5,6-Dimethylxanthenone-4-acetic acid (DMXAA) is a low molecular weight drug of the flavonoid group, which has an anti-vascular effect in tumours causing endothelial cell apoptosis and activation of cytokines. Flavonoid-based compounds have been reported to lead to an upregulation in the expression of lysophosphatidylcholines (LPC)-type lipids in solid tumours. A study employing TLC/MALDI-MS and MALDI-MS imaging to examine LS174T colorectal adenocarcinoma xenografts following administration of DMXAA has been conducted into this effect. METHODS: LS174T colorectal adenocarcinoma xenografts grown in male immune-deficient mice were treated with 27.5 mg/kg DMXAA. The control (before treatment) and 4 h and 24 h post-treatment tumours were excised and divided into two. MALDI-MS imaging experiments were carried out on 12 microm cryosections sections taken from one half of the tumours and from the other half the lipids were extracted and analysed by TLC/MALDI-MS. These experiments were carried out in triplicate. RESULTS: Statistical analysis of the MALDI-MS imaging data set indicated an increased amount of LPC in the 24 h post-treated sample and a decreased amount of PC in the 24 h post-treated sample, compared with the 4 h post-treated sample and the control. These effects were confirmed by the TLC/MALDI-MS data. The lipid extracts were separated into six spots on the TLC plate. These were identified as arising from different lipids classes, i.e. LPC, sphingomyelins (SM), phosphatidylcholines (PC) and phosphatidylethanolamines (PE). The TLC/MALDI-MS data indicated that LPC were highly expressed in the 4 h and 24 h post-treated tumour samples compared with the control. Examination of the mass spectrometric images confirms this increase and demonstrates additionally that the increase in the signals arising from LPC appears to be localised primarily within the central areas of the xenograft. CONCLUSIONS: An increase in expression of LPC lipids in solid tumours treated with DMXAA has been demonstrated and shown to be localised in the central area of the tumour.

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: In this study, the analysis of ammo acids usmg High Performance Liquid Chromatography (HPLC) with pre-column derivatisation was optimised. The derivatisation reagents include o-phthaldialdehyde (OPA), 9- fluorenylmethylchloroformate (FMOC) and iodoacetic acid (IDA). Detection was performed using UV and fluorescence in series. The developed method was utilised for the analysis and quantitation of amino acids in eighteen wines. The application of chemometric data evaluation was initiated. / AFRIKAANSE OPSOMMING: Hierdie ondersoek behels die optimisering van die aminosuuranalise deur gebruik te maak van Hoë Druk Vloeistof Chromatografie (HDVC) in kombinasie met pre-kolom derivatisering. Die derivativatiserings reagense sluit in o-phthaldialdehied (OPA), 9- fluorenielmetielchloroformaat (FMOC) en jodoasynsuur (IDA). Deteksie is gedoen deur gebruik gemaak van 'n ultraviolet (UV) en 'n fluorosensie detektor in serie. Die metode sodoende ontwikkel is gebruik vir die analise en kwantifisering van aminosure in agtien wyne. Die toepassing van chemometriese data evaluasie is ook geïnisieer.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study describes: · Development of analytical tools to investigate the light struck flavour (LSF) in beer by Gas chromatography mass spectrometry (GCMS) and by liquid chromatography mass spectrometry/mass spectrometry (LCMS/MS). Development of a high performance liquid chromatography (HPLC) method to analyse carbohydrates in beer. · The efficiency a pilot scale ultraviolet (UV-C) system at 254 nm to inactivate spoilage microorganisms spiked in commercial beer. Bacteria test were Lactobacillus brevis, Acetobacter pasteurianus and Saccharomyces cerevisiae · A pilot scale UV treatment of commercial and non-commercial lager beers at UV dosage of 1000 J/L. Following the UV treatment, the correlation between chemical analyses and sensory tests conducted by consumers’ tasters were investigated. · A pilot scale UV treatment of non-commercial beer brewed with reduced hops iso-α-acids (tetrahydro-iso-α-acids) at UV dosage of 1000 J/L. Sensory changes and chemical properties were investigated. · The development and optimisation of an UV light emitting diodes (UV-LED) bench scale apparatus. Chemical and microbiological tests were conducted to investigate the effect of UV-LEDs on beer at 250 nm and 275 nm wavelengths. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf: · Die ontwikkeling van analitiese toerusting om die invloed van lig op die smaakontwikkeling in bier te bestudeer m.b.v gaschromatografie massa spektrometrie (GCMS) en vloeistofchromatografie massa spektrometrie/massa spektrometrie, asook die ontwikkeling van ‘n hoë druk vloeistofchromatografiese metode vir die analise van koolhidrate in bier. · Die doeltreffendheid van ‘n toetsskaal ultraviolet (UV-C) sisteem om die nadelige mikroorganismes waarmee die bier geïnnokuleer was, by 254 nm te inaktiveer.. Toetse is uitgevoer met die volgende bakterieë, Lactobacillus brevis, Acetobacter pasteuriants en Saccharomyces cerevisiae. · ‘n Toetsskaal UV behandeling van kommersiële en nie-kommersiële lager biere by ‘n UV dosering van 1000 J/L. Na UV behandeling is die verwantskap tussen chemiese analises en ‘n reeks sensoriese toetse deur vebruikers proeërs ondersoek.. · ‘n Toetsskaal UV behandeling van ‘n nie-kommersiële bier gebrou met verlaagde hops-iso-α-sure (tetrahidro-iso-α -sure) by UV dosering van 1000 J/L. Sensoriese veranderinge asook chemiese eienskappe is ondersoek. · Die ontwikkeling en optimalisering van ‘n UV-lig emissie diodes bankskaal apparaat. Chemiese en mikrobiologiese toetse is uitgevoer om die effek van UV lig op bier by 250 nm en 275 nm te ondersoek.

Lipids are important for the structural and physiological functions of neuronal cell membranes. Alterations in their lipid composition may result in membrane dysfunction and subsequent neuronal deficits that characterise various disorders. This study focused on profiling lipids of aged and LPS-treated rat brain and liver tissue with a view to explore the effect of atorvastatin in neuroinflammation, and examining lipid changes in different areas of rat brain of the Flinders Sensitive Line (FSL) rats, a genetic model of depression. Lipids and other analytes extracted from tissue samples were analysed with proton nuclear magnetic resonance spectroscopy (1H-NMR), gas chromatography (GC) and liquid chromatography-tandem mass spectroscopy (LC/ESI-MS/MS). Changes in the lipid profiles suggested that brain and liver responded differently to ageing and LPS-induced neuroinflammation. In the aged animals, n-3 PUFA were reduced in the brain but were increased in the liver. However, following treatment with LPS, these effects were not observed. Nevertheless, in both models, brain concentration of monounsaturated fatty acids was increased while the liver was able to maintain its monounsaturated fatty acid concentration. Atorvastatin reversed the reduction in n-3 PUFA in the aged brain without reducing brain and liver concentration of cholesterol. These findings further highlight alterations in lipid metabolism in agerelated neuroinflammation and show that the anti-inflammatory actions of atorvastatin may include a modulation of fatty acid metabolism. When studying the FSL model, there were differences in the lipid profile of different brain areas of FSL rats compared to Sprague-Dawley controls. In all brain areas, arachidonic acid was increased in the FSL rats. Docosahexaenoic acid and ether lipids were reduced, while cholesterol and sphingolipids were increased in the hypothalamus of the FSL rats. Furthermore, total diacylglycerophospholipids were reduced in the prefrontal cortex and hypothalamus of the FSL rats. These results show differences in the lipid metabolism of the FSL rat brain and may be suggestive of changes occurring in the brain tissue in depression.

In this experiment, more than one hundred volatile organic compounds were analyzed with the gas chromatograph. Six capillary columns ZB wax plus, ZB 35, TR1MS, TR5, TG5MS and TG1301MS with different polarities have been used for separation of compounds and illicit drugs. The Abraham solvation model has five solute descriptors. The solute descriptors are E, S, A, B, L (or V). Based on the six stationary phases, six equations were constructed as a training set for each of the six columns. The six equations served to calculate the solute descriptors for a set of illicit drugs. Drugs studied are nicotine (S= 0.870, A= 0.000, B= 1.073), oxycodone(S= 2.564. A= 0.286, B= 1.706), methamphetamine (S= 0.297, A= 1.570, B= 1.009), heroin (S=2.224, A= 0.000, B= 2.136) and ketamine (S= 1.005, A= 0.000, B= 1.126). The solute property of Abraham solvation model is represented as a logarithm of retention time, thus the logarithm of experimental and calculated retention times is compared.