M.Sc. / The continued use and popularity of plant based traditional medicine necessitates scientific validation of the therapeutic potential of medicinal plants through phytochemical and pharmacological screening as well as the isolation and identification of bioactive compounds. Since the pharmacological effectiveness of medicinal plants is affected by several intrinsic and extrinsic factors, studies on the variations on chemical composition and biological activity are important as well. These provide a scientific rationale for using plants from different regions for the same medicinal purposes and allow traditional healers and consumers to make informed decisions with regard to the collection and use. Rapanea melanophloeos is a popular medicinal plant from the Myrsinaceae family widely distributed in southern Africa. It‟s bark, fruits and rarely the leaves are used traditionally for ailments ranging from stomach disorders, respiratory problems to disorders of the nervous system. Available chemical information reports on the accumulation of benzoquinones as major compounds, as well as some triterpenoid saponins and tannins. In view of the plant‟s wide distribution and medicinal use of different plant parts, this study comparatively evaluated the chemical composition of various crude extracts of the leaves, fruits and bark of plants collected from six localities. This was coupled with antibacterial tests to evaluate the therapeutic potential of different solvent extracts of the leaves, fruits and bark as well as the isolation of bioactive compounds from the fruits. Plants were collected from six different localities between Swaziland and South Africa and sequentially extracted with petroleum ether, ethyl acetate, methanol and water as a series of increasingly polar solvents. Thin layer chromatography (TLC), Gas-Chromatography/Mass spectrometry (GC-MS) and High Performance Liquid Chromatography (HPLC) were used to obtain a semi-quantitative chemical composition profile of different extracts. The TLC fingerprints of petroleum ether, ethyl acetate and methanol extracts showed the accumulation of non-polar terpenes, benzoquinones, saponins, tannins and flavonoids in the three plant parts. Slight variations in the chemical composition of the leaves, bark, and fruits were noted. Some components occurred in specific plant parts and others occurred in all three plants. The chemical profile of the leaves and bark were quite comparable in most instances with the fruits showing a generally different profile. This confirms previous literature reports on the comparability of leaves and the bark accounting for interchangeable use in traditional medicine.

M.Sc. (Chemistry) / The storage as solid Ag12BI(s) of reactor produced 12BI (t~ = 1.6 x 107 a) in underground respositories can present an environmental problem due to the potential release of radioactive 12BI into the environment over extended storage periods. One process that causes concern is the solubilization of AgI through complexation when brought into contact with underground water, particularly those with high salt content. In this work the charaqterization of the complexation equilibria in the AgI(s)/I-(aq),CI-(aq) system was studied. Solu- I tions containing high CI- and low 1- concentrations were of special interest with regard to the possible formation of ternary complexes. The presence of AgICI22- was indicated experimentally but no evidence of other ternary species like AgI2CI2- or AgIsCIS- could be established. Solubilities were determined radiochemically by using specially prepared 110mAgI. Solubility curves for AgI in different I-/CI- mixtures were adequately explained in terms of models consisting of the species AgCls2-, AgC14S-, AgIs2-, AgI4s- and AgICI22-. Distribution curves were calculated for different I-/CI- mixtures. As an alternative detection mode for silver-determination a flow injection system incorporating a micro-column of activated alumina was used in conjuntion with flame atomic absorption spectrometry for the pre-concentration and determination of silver in water. The procedure was successfully applied to a range of water samples, but no determination of silver in halide or perchlorate media was possible. The limit of detection based on a sample volume of 15 cms was 4.5 ~gdm-3 and the relative standard deviations at 50 and 5 ~gdm-3 were 5.4 and 19%, respectively. In part B of this work a method for the determination of chloride in organic compounds (oils provided by the Atomic Energy Corporation) by using an Parr oxygen bomb and ion chromatography was studied. The combustion products were absorbed in H20. The solution was injected into an ion chromatograph equipped with an anion analytical column, membrane suppressor and conductivity detector. The instrument response was calibrated using different standard solutions. These were prepared from several organic solutions, an organic salt and from sodiumchloride. Calibration curves were linear over a wide range and presented good reproducibility. It differed however according to the type of standard solution used. The limit of detection was 255 ~gdm-3 and the relative standard deviations at 10, 1 and 0.5 ugcm-3 were 0.52, 1.64 and 3.5%, respectively. As an alternative decomposition method wet decomposition within a sealed system (autoclave) was used. Due to the high blank values in this method no analysis of substances could be made in the lower ugcm-3 range.

Ph.D. / The main objective of this study was to investigate the presence, variations and the fate of lipophilic extractives during all the stages in the dissolving pulp production process. Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp which are soluble in organic solvents. Their presence in wood and pulp has negative effects on both the pulping process and the quality of the produced dissolving pulp. Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites (Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites and that the woods at the Ixopo site were found to have the highest amount of lipophilic extractives. The quantitative variation of lipophilic extractives in wood was found to be significantly affected by respective sites and tree species. The principal component analysis (PCA) model, which was used to correlate soil parameters and amount of lipophilic extractives in woods per each site, revealed that high amounts of lipophilic extractives were found in trees grown at sites with a high composition of clay soil and organic matter. Thus if the industry is to avoid the high levels of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and unsaturated sterols in particular were found to positively correlate with the Kappa number, thus affecting its measurement.The main objective of this study was to investigate the presence, variations and the fate of lipophilic extractives during all the stages in the dissolving pulp production process. Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp which are soluble in organic solvents. Their presence in wood and pulp has negative effects on both the pulping process and the quality of the produced dissolving pulp. Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites (Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites and that the woods at the Ixopo site were found to have the highest amount of lipophilic extractives. The quantitative variation of lipophilic extractives in wood was found to be significantly affected by respective sites and tree species. The principal component analysis (PCA) model, which was used to correlate soil parameters and amount of lipophilic extractives in woods per each site, revealed that high amounts of lipophilic extractives were found in trees grown at sites with a high composition of clay soil and organic matter. Thus if the industry is to avoid the high levels of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and unsaturated sterols in particular were found to positively correlate with the Kappa number, thus affecting its measurement. Viscosity of pulp which is an important quality parameter was also found to be positively influenced by sterol residues, whereas the reducing properties of pulp were found to be affected by sterols and saturated fatty acids with a carbon chain length of less than C20.

No description available.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / In this dissertation the physical and chemical alterations induced by mastication and manipulation of wax by the worker bee in honeycomb construction, and the subsequent contribution afforded the structural integrity of the nest, are elucidated. In comb building, the freshly secreted wax scales are mandibulated together with a frothy salivary emulsion, and added piece-meal to form honeycomb. Textural modifications were revealed using X-ray crystallography. While virgin scale wax is highly structured, with the crystallites aligned approximately perpendicular to the planar surface, comb wax has a random crystallographic arrangement. This reflects a disruption of the crystallite structure following the mechanical insult of mastication. Chemical analyses included investigation of both lipid and proteinaceous elements. Lipid composition was evaluated by enzyme-catalyzed as well as thin-layer and gas-liquid chromatographic methods. The results indicate a reduction in scale diacylglycerols with a corresponding increase in comb saturated monoaeylglycerols. Such modifications are highly suggestive of lipase activity within the salivary addition. The proteins of comb and scale wax were analyzed electrophoretically, under reduced conditions. Each wax possesses unique polypeptide fractions, in addition to sharing common protein species, It is speculated that those in common represent integral proteins, such as transport molecules, while the disparities noted may be due to salivary enzymatic degradation, or even glycosylation. The effects of these textural and chemical alterations on the mechanical behaviour of the waxes was assessed. Tensile tests were performed on a variety of scale and comb wax preparations over the range of temperatures likely to impinge on the honeybee nest. These investigations reveal the specific structural contributions made by each of the physico-chemical alterations described. Further, they demonstrate that while scales are ideal moulding materials due to their high distensibility and low stiffness, the greater resistance to deformation and lower potential for extension makes comb wax a superior structural material. The mechanical advantage for including propolis and cocoon silk within the comb structure was also investigated. Tensile testing indicates that the resultant composite material is structurally superior, largely due to the presence of silk reinforcement. / Andrew Chakane 2018

Hemoglobin, from the erythrocytes of adult and fetal pigs, was isolated and analyzed by carboxymethylcellulose column chromatography and electrophoresis on polyacetate. These techniques demonstrate the existence of four fetal components (F0, F1A, F1B, F1C) and two adult components (A0, A1) based on their elution pH values and electrophoretic mobilities. The shift from-fetal to adult forms is initiated sometime between eight weeks after birth and one year. The change is not completed until sometime after one year and the major fetal forms (F0, F1A) maintain a 15% level in a mature adult. This report is in contrast with the results of early work that indicated that pig hemoglobin was homogeneous in nature. It conforms to the work by other researchers on other animals by showing that pig hemoglobin is heterogeneous.

No description available.

This study focuses on the utilization of metal-dependent monoclonal antibodies for large-scale chromatography and addresses an aspect that has been cited to lower immunosorbent performance, namely "orientation" of antibodies on matrices. The antibodies used in this study, the "EDTAdependent" 7D7BlO and the "Ca²⁺ -dependent" HPC4 are directed against human Protein C (PC). The 7D7BI0 antibody was characterized in terms of its metaldependency and specificity. The region of PC (epitope) recognized by 7D7BlO was identified as the first 15 residues in the NH₂-terminal. Immunosorbents made with 7D7BI0 provided highly pure and functional PC. The "orientation" of the antibodies on matrices was addressed in two ways. In the first approach, performance of immunosorbents coupled through carbohydrate moieties were compared with immunosorbents coupled through peptide regions. Coupling via carbohydrate linkages, which is generally believed to be Fc-directed, did not have any advantage in terms of efficiency and recovery over coupling via peptide. / Ph. D.

Atomic emission spectroscopy is a powerful method for chemical analysis because it offers convenient qualitative and quantitative determination of the elemental composition of an analytical sample. Although most frequently used to determine the total concentration of a given analyte, atomic spectroscopy may be coupled with a separation technique to aid in the elemental identification of individual species. Recently, supercritical fluid chromatography (SFC) has gained popularity among the research community partially because SFC is much more tolerant of polar functional groups than is gas chromatorgraphy (GC). SFC can be used in applications where derivatization is not possible due to sample complexity or steric hindrance. However, these polar compounds often require the addition of polar organic solvents to SFC to improve retention characteristics and peak shape. These polar modifiers reduce or eliminate the utility of flame-based detectors. Therefore, researchers have begun to look for alternative detection systems for SFC with polar modifiers. In particular, atomic emission based detectors using plasmas have become popular to fill this void. This research stems from several characteristics that the plasma based detectors possess which make them more appealing than flame-based photometric detectors. These characteristics include improved analytical sensitivity, fewer spectral interferences, a wide dynamic range and the ability to tolerate polar organic modifiers. Possibly the most important attraction of the plasma detector is, with respect to chromatographic analyses, that this detector allows analysis of compounds that co-elute from a column because the detector is element-specific. The evaluation of the high efficiency microwave induced plasma (HEMIP) as an elemental selective detector for packed column supercritical fluid chromatography has been explored in this dissertation. The effect of CO₂ introduction on the analytical parameters of the plasma, the feasibility of coupling packed column supercritical fluid chromatography to the argon HEMIP for the determination of metals, the use of a helium sustained plasma for nonmetal determinations, and the application of the He-HEMIP as a sensitive and selective detector for packed-column SFC. / Ph. D.

An explosive vapor generator which produces transient "clouds" of explosive vapors for use in the evaluation of commercial explosive vapor detection systems has been developed based on a capillary gas chromatograph. The design of the vapor generator replaces a flame ionization detector on the gas chromatograph with an effluent heater system to provide a cloud of explosive vapor while preventing condensation onto the walls of the capillary column. This vapor source has been successfully used to produce vapors of dinitrotoluene (DNT), trinitrotoluene (TNT), and 1,3,5-trinitro-1,3,5- triazacyclohexane (RDX). The chemical composition of the output was confirmed by both ion mobility spectrometry, and quadrupole mass spectrometry. Adsorptive effects of TNT and RDX were studied in order to optimize the injection parameters, achieving detection limits three orders of magnitude lower than previously reported. The quantitative output of the system was verified using thermal tube desorption gas chromatography. / Ph. D.