Dissertation (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: DFT calculations employing the B3LYP functional were done to investigate the mechanism for the Ni-catalyzed hydrocyanation of ethylene as proposed by Tolman. Although this reaction is an important industrial process, its mechanism has never been studied computationally, apart from calculations pertaining to ligand tailoring. This study comprises a detailed configurational analysis of each step of the reaction cycle, charge decomposition analysis of pertinent species and analysis of the activation barriers involved at each step. A model ligand, PH3, is employed, due to its electronic similarity to the experimental ligand most widely used, P(O-o-tolyl)3, and its small size, which makes it amenable for calculations at this level. It was found that oxidative addition of HCN to the precursor complex (ethylene)NiL2 (L=PH3) can take place in one step and that it is the rate-determining step in the gas phase. The resulting adduct has H+ (which becomes a hydride) and CN- coordinated in the cis configuration. Ligand dissociation yields three configurations of (ethylene)-NiHCNL, of which only two can participate in the catalytic cycle. It is shown that this is because migration-insertion of ethylene into the Ni-H bond takes place before, or concomitant with, association of a second ethylene molecule, contrary to expectation. This path therefore requires that ethylene and hydrogen are coordinated in the cis configuration, something only possible for two of the three isomers of (ethylene)NiHCNL. The calculations support the mechanism of associative reductive elimination and shows that elimination can only take place if the ethyl and cyanide groups are in the cis configuration. Analysis of the energetic profile of the reaction shows that entropy effects play a very important role in the propagation of the cycle, at least in the gas phase. Preliminary work on the effect of Lewis acids the catalytic cycle is presented, with structural and energetic analysis. An important general conclusion is that the standard way of representing the energy profile of reactions where intermolecular transitions (as opposed to intramolecular transitions only) take place can be misleading. It will be argued that the implicit assumption that two species which are minimum energy structures on distinct potential energy surfaces will also be an energy minimum on one potential energy surface skews the energy profile of the reaction. The consequence of this is that care must be taken in representing energy profiles for reactions where more than one distinct species participates. / AFRIKAANSE OPSOMMING: Die meganisme, soos deur Tolman voorgestel, van die Ni-gekataliseerde hidrosianering van etileen word ondersoek met behulp van Kohn-Sham elektrondigtheidsteorie (density finctional theory, DFT) berekeninge waarin die B3LYP-funksionaal gebruik word. Alhoewel die reaksie ‘n belangrike proses is in die industrie, is die volle me-ganisme nog nooit met behulp van berekeninge bestudeer nie. Daar is egter wel al werk gedoen aangaande sekere aspekte van die reaksie, byvoorbeeld ligandontwerp. Hierdie studie behels ‘n noukeurige konfigurasionele analise van elke stap van die reaksie-siklus, ladingsverdelingsanalise (charge decomposition analysis, CDA) van sekere belangrike spesies asook die analise van die energiestappe betrokke by elke stap. Fosfien is gekies as ‘n modelligand, omdat dit elektronies ooreenstem met P(O-o-toliel)3, die ligand wat meestal in eksperimentele werk gebruik is. Die klein grootte van fosfien maak dit ook geskik vir be-rekeninge op hierdie vlak. Daar is bevind dat die oksidatiewe addisie van HCN aan die voorgangerkompleks (etileen)-NiL2 (L=PH3) in een stap kan plaasvind en in die gasfase snelheidsbepalend is. Die adduk (ettileen)NiHCNL2 bevat H+ (wat ‘n hidried word) en CN- in die cis-posisie relatief tot mekaar. Liganddissosiasie lewer drie isomere van (etileen)NiHCNL. Daar is bevind dat slegs twee van dié isomere aan die katalitiese reaksie kan deelneem, omdat die migrasie-inplasing (migration-insertion) van etileen in die Ni-H-binding voor, of saam met, die assosiasie van ‘n tweede etileen-molekule plaasvind. Dit is slegs moontlik indien waterstof en etileen cis teenoor mekaar is, wat geld vir twee van die isomere. Die meganisme van assosiatiewe reduktiewe eliminasie word deur die berekeninge gerugsteun. Voorts blyk dit vanuit die berekeninge dat die etiel- en sianiedgroepe cis teenoor mekaar moet wees voordat reduktiewe eliminasie van propionitriel kan plaasvind. Analise van die energetiese profiel van die reaksie toon dat entropie-effekte ‘n belangrike rol speel in die voortsetting van die reaksie in die gasfase. Die invloed van Lewissure op die katalitiese siklus word, met behulp van strukturele en energetiese analise bespreek. ‘n Belangrike algemene gevolgtrekking is dat die standaardvoorstelling van die energetiese profiel van reaksies waarin intermolekulêre oorgange (teenoor slegs intramolekulêre oorgange) voorkom, misleidend kan wees. Dit word gestel dat die implisiete aanname dat twee spesies wat minumum-energiestrukture verteenwoordig op twee verskillende potensiële energie-oppervlaktes ook ‘n minimum-energiestruktuur voorstel op een potensiële energie-oppervlakte, die energieprofiel skeeftrek. Gevolgtrekkings vanuit hierdie energieprofiele van reaksies waar meer as een onderskeibare spesie deelneem, moet dus met omsigtigheid gemaak word.

Thesis (PhD)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Radiochemical research involving ion exchange chromatography is of paramount importance to the future of radionuclide production at the Radionuclide Production Group (RPG) of iThemba LABS. It is required for the production of high-activity yields of radionuclides to effectively remove impurities and for the safety of the operators performing such productions. The radiochemical separations of some new products from their target material, as well as experiments to determine whether production is viable, are described. 67Ga is currently being produced at the RPG and makes use of zinc targets. With the production of ultra-pure 67Ga, it was necessary to remove any Fe(III) impurities from the final product, such that it may be possible to label peptides with this product. The use of Amberchrom CG161M for this purpose was found to be satisfactory. Interest was shown in 88Y by an overseas company for the manufacture of sources. While a method involving extraction of the radionuclide and the ion exchange thereof using Chelex 100 chelating resin had been published, problems with the production persisted. Three methods, using ion exchange chromatography, were devised to produce the radionuclide, with two of them being adopted for production purposes. Thick-target nuclear data have also recently been accumulated in collaboration with colleagues from ATOMKI, Debrecen, Hungary. There is a large demand for 82Sr for the manufacture of 82Sr/82Rb generators for medical use. A method was developed to manufacture this radionuclide with thicker (32 g) target material, bombarded in the Vertical Beam Target Station (VBTS), and to separate 82Sr from its target material with the use of Purolite S950 chelating resin. 68Ge/68Ga generators are becoming increasingly important in the world of radiopharmaceuticals. A project to develop a local generator was funded by the Innovation Fund and research was performed to produce 68Ge, such that the generator could be manufactured. This involved bombarding thicker Ga targets in the VBTS and performing the chemical separation using AG MP-1 anion exchange resin. The final product was loaded onto generators, although tests performed on different materials to the ones being marketed are also reported in this work. A project was initiated to study the cluster radioactive decay of 223Ac via 14C and 15N emission. To produce 223Ac for these observations, a Th target was bombarded. The 227Pa was separated from the target material using AG MP-1 macroporous anion exchange resin and used as a source, which decayed to 223Ac. The chemical separation and the drying of the final product onto a source plate were completed within approximately 70 minutes from the end of bombardment. The work was performed in collaboration with JINR, Russia, and University of Milan and INFN, Italy. 133Ba has a half-life of over 10 years and is an expensive radionuclide to produce. It has been used in medical and biological studies and there still appears to be a demand for it. A method was devised, utilizing AG50W-X4 cation exchange resin, to separate 133Ba from its CsCl target material. Agricultural specialists in the past have shown an interest in 28Mg, to determine the uptake of the element in fruit. It has long been regarded by some of the local researchers as an interesting project to investigate. It has been determined that the product can be produced in reasonable quantities using LiCl target material, with ten targets being bombarded in series using a 200 MeV proton beam delivered by the Separated Sector Cyclotron. A method, involving the use of Purolite S950 chelating resin, was devised to separate 28Mg from its target material. / AFRIKAANSE OPSOMMING: Radiochemiese navorsing, wat ioonuitruiling chromatografie behels, is van uiterste belang vir die toekoms van die produksie van radionukliede by die Radionukliedproduksiegroep (RPG) van iThemba LABS. Dit is nodig vir die hoë aktiwiteit opbrengs van radionuklied produkte om onsuiwerhede te verwyder en vir die veiligheid van die operateurs wat die produksies moet uitvoer. Die skeiding van nuwe produkte van hulle skyfmateriaal, sowel as eksperimente om vas te stel of ‘n produksie uitvoerbaar is, word in die werk beskryf. 67Ga word tans by RPG vervaardig en maak gebruik van sink as skyfmateriaal. Vir die produksie van “ultra-suiwer” 67Ga was dit belangrik om enige Fe(III) onsuiwerhede uit die finale produk te verwyder om sodoende peptiede merking te kan uitvoer. Die gebruik van Amberchrom CG161M hars was voldoende vir dié eksperiment. ‘n Oorsese maatskappy het belangstelling getoon in 88Y vir die vervaardiging van bronne. Alhoewel ‘n metode wat die ekstraksie van die radionuklied en die ioonuitruiling daarvan met die gebruik van Chelex 100 chelerende hars reeds gepubliseer was, het probleme met die produksie voortgeduur. Drie metodes is opgestel om 88Y te produseer, waarvan twee van die metodes tans gebruik word vir produksie doeleindes. Dik-skyf kerndata is ook versamel in samewerking met kollegas van ATOMKI, Debrecen, Hongarye. Daar is ‘n groot aanvraag vir 82Sr vir die vervaardiging van 82Sr/82Rb generators vir mediese doeleindes. ‘n Metode is ontwikkel om die radionuklied te vervaardig van dikker skyfmateriaal (32 g), in die Vertikale Bundelstasie gebombardeer, en om 82Sr van sy skyfmateriaal te skei met die gebruik van Purolite S950 chelerende hars. 68Ge/68Ga generators is besig om toenemend belangrik te word in die wêreld van radiofarmasie. iThemba LABS kry baie navrae om die produk te vervaardig. Die projek was ook deel van die voorlegging aan die “Innovation Fund” en ‘n manier is ondersoek om 68Ge te vervaardig, wat benodig word om so ‘n generator te laai. Dik Ga skyfmateriaal word in die Vertikale Bundelstasie gebombardeer en ‘n chemiese skeiding is uitgevoer deur gebruik te maak van AG MP-1 anioonuitruiling hars. Die finale produk is op die generators gelaai vir toetsdoeleindes. Toetse is ook op ‘n ander tipe generator uitgevoer en word in die werk beskryf. ‘n Projek is begin om “cluster” radioaktiewe verval van 223Ac, via 14C en 15N emissie, te bestudeer. ‘n Th-skyf is met protone gebombardeer om die 223Ac te produseer vir die eksperiment. 227Pa is vervaardig en geskei van die skyfmateriaal. Dit is gedoen met die gebruik van AG MP-1 makroporeuse anioonuitruiling hars en drooggemaak op ‘n bronplaat, waar dit verval het na 223Ac. Die chemiese skeiding en die droogmaak van die finale produk op ‘n bronplaat is uitgevoer binne 70 minute na Einde van Bombardering (EVB). Die werk is deel van ‘n samewerking met kollegas van JINR, Rusland, en die Universiteit van Milaan, sowel as INFN, Italië. 133Ba het ‘n halveertyd van oor die tien jaar en is ‘n duur produk om te vervaardig. Dit is al gebruik in mediese en biologiese studies en daar is deesdae ‘n redelike aanvraag daarvoor. ‘n Metode is uitgewerk om 133Ba te skei van die CsCl skyfmateriaal met die gebruik van AG50W-X4 katioonuitruiling hars. Spesialiste in landboustudies het in die verlede belangstelling getoon in 28Mg. Dit word gebruik om die absorpsie van dié element in vrugte te ondersoek. Die produk kan vervaardig word met die gebruik van LiCl skyfmateriaal: tot soveel as tien skywe (agter mekaar) word gebombardeer met ‘n 200 MeV protonbundel te iThemba LABS. ‘n Metode, wat Purolite S950 behels, is daargestel om 28Mg van die skyfmateriaal te skei.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / Video 1: Twin-bearing Döhne Merino ewe butting only one of her lambs in typical rejection behavior. Rejection of one twin is not a common phenomenon. (Video by Dr Marlize Viviers) / Video 2: Twin-bearing ewe # 22 accepting alien lamb # 179. The alien lamb wears a jacket her other lamb has been wearing for the preceding 24 hours. The excessive sniffing at the jacket, bleating and looking around show that the ewe is not totally satisfied with the situation. (Video by Dr Marlize Viviers) / Video 3: Ewe # 22 rejecting alien lamb # 179 after removal of the jacket it has worn in the previous video. (Video by Dr Marlize Viviers) / ENGLISH ABSTRACT: Sheep husbandry substantially contributes to South Africa’s economy. Lamb mortality is regarded as a major constraint to sustainable sheep production, and an important factor in lamb survival is the strong ewe–lamb bonding. This is a well-known phenomenon in all sheep races and strong evidence exists that the selective ewe–lamb bond formation has a pheromonal basis, in that the ewe can distinguish her lamb by its unique, familiar smell. Sheep farmers and scientists have examined various methods of making alien lambs acceptable to foster ewes. The survival rate of offspring could be substantially increased if a reliable method could be devised to prevent ewes from rejecting their own lambs or if ewes could be induced to accept alien lambs. A better understanding of the semiochemicals involved in this communication between ewe and offspring could facilitate the development of a method by which ewes can be coaxed into adopting foster lambs. This would positively contribute to efficient sheep production in South Africa. The objective of this study was to characterise the volatile constituents present in the wool and the amniotic fluid collected from the Döhne Merino lambs to achieve a better understanding of the ewe–lamb semiochemical communication. The volatile organic constituents associated with the wool and amniotic fluid were characterised and a total of 133 volatile organic compounds were identified. Several compound classes are represented in these samples and the majority of these compounds have previously been identified in the excretions and secretions of numerous mammalian species. A number of different aspects of ewe–lamb kin recognition were investigated. First, the odour profiles of twin lambs were compared to those of other twins. The results of these analyses revealed that the wool volatiles of twin lambs are qualitatively as well as quantitatively practically identical, but different from those of other lambs in the flock. Second, the change in the odour profiles of lambs was studied over a seven-day period. It was found that the odour profiles of lambs are not fixed, and for as long as a ewe makes use of olfactory recognition as the main mode of identification of her lamb she has to continue learning the odour of her lamb. Third, the amniotic fluid was investigated as a possible source of maternal labels, i.e. as chemical codes consisting of mixtures of compounds in specific quantitative ratios that are imprinted on lambs by their mothers at birth. It was found that the amniotic fluids of first- and second-born lambs are qualitatively and quantitatively different. It is possible that the duration of the lambing birth process could contribute to this change in amniotic fluid composition. Fourth, the role of residual proteins in the dissemination of the semiochemicals involved in ewe– lamb communication was investigated and six proteins were identified as amniotic fluid and wool-associated proteins. Bioassays carried out during the lambing season of 2009 confirmed the role of the odour of the lamb in ewe-lamb recognition, but bioassays carried out with synthetic pheromone formulations gave inconclusive results. / AFRIKAANSE OPSOMMING: Skaapboerdery lewer aansienlike bydrae tot die ekonomie van Suid Afrika, maar lamsterftes is een van die kwellende probleme waarmee kleinveeboere te kampe het. Die eksklusiewe band wat binne die eerste paar uur na 'n lam se geboorte tussen die ooi en haar lam ontwikkel, is die hooffaktor waarvan lammers se oorlewing afhang. Hierdie sterk binding tussen lam en ooi is 'n bekende verskynsel in alle skaap-rasse en dit is bekend dat 'n feromoon wat deur die lam vrygestel word, dit vir die ooi moontlik maak om haar lam aan sy unieke reuk uit te ken. Lamsterftes sou aansienlik verminder kon word as hierdie feromoon geïdentifiseer en gebruik kan word om ooie te verhoed om hulle eie lammers te verwerp en om die aanvaarding van vreemde lammers deur ooie moontlik te maak. Die doel van hierdie studie was die chemiese karakterisering van die vlugtige organiese verbindings aanwesig in die amniotiese vloeistof en wol van Döhne Merino lammers ten einde 'n beter begrip van die semiochemiese kommunikasie tussen ooie en lammers te verkry. In die amniotiese vloeistof is 70 vlugtige organiese verbindings geïdentifiseer. Dieselfde verbindings asook 'n verdere 63 verbindings is in lammerwol geïdentifiseer. Die meerderheid van hierdie verbindings is reeds voorheen in verskeie soogdierafskeidings gevind. Die studie het verskeie interessante aspekte van hierdie semiochemiese kommunikasie aan die lig gebring. Eerstens is daar gevind dat die samestelling van die vlugtige organiese materiaal in die wol van tweelinglammers, oftewel hul reukprofiele, feitlik identies is. Verder verskil die reukprofiele van 'n tweeling van dié van ander tweelinge en enkelinge in die trop. Tweedens is gevind dat die reukprofiel van 'n lam nie by geboorte vasgelê word en so behoue bly nie, maar dat dit geleidelik verander oor ten minste die periode van sewe dae waaroor hierdie verskynsel bestudeer is. Dit noodsaak die ooi om haar geheue met betrekking tot die lam se reuk voortdurend te verfris gedurende die tydperk wat sy hoofsaaklik van haar reuksin gebruik maak om haar lam te herken. Derdens is die amniotiese vloeistof ondersoek as moontlike bron van ‘n sogenaamde moedermerk, waardeur chemiese mengsel van verbindings wat in ‘n spesifieke kwantitatiewe samestelling by geboorte deur die ooi op haar lam agter gelaat word. Ten opsigte van kwalitatiewe en kwantitatiewe samestelling, verskil die vlugtige organiese fraksie van die amniotiese vloeistof van die tweelinglam wat eerste gebore word van die amniotiese vloeistof van die lam wat tweede gebore word. Dit is onwaarskynlik dat amniotiese vloeistowwe wat ten opsigte van hul vlugtige organiese fraksies van mekaar verskil, nagenoeg identiese moedermerke op tweeling lammers sou kon laat. Vierdens is vasgestel dat spore van ses proteïene uit die amniotiese vloeistof op die wol van lammers agtergelaat word. Daar kon ongelukkig nie vasgestel word of hierdie proteïene 'n rol in die vrystelling van semiochemiese inligting speel nie. Gedragstoetse wat tydens die lamseisoen van 2009 uitgevoer is, het bevestig dat die lam se reukprofiel deurslaggewende rol in ooi-lam herkenning speel, maar gedragstoetse wat met sintetiese feromoonmengsels uitgevoer is, het onbesliste resultate opgelewer.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Polyacrylonitrile, (PAN), polymers are of interest due to their many unique characteristics in comparison to most other fibre forming polymers. The focus of this study was the effect of electrospinning variables and additives on their unusual thermal properties and internal molecular morphology with the objective of improving the performance of this fibre in industrial application, or at least contributing to the understanding of how the fibre processing variables affect the thermal performance. The process of electrospinning was used to process samples of PAN fibres with additives in order to determine their effect on the molecular orientation and crystallinity of the resultant nano- and micronsized fibres. The effect of additives in the forms of low molecular weight oligomers, blends of conductive polymers and nanoparticles and conductive salts (mainly copper and lithium based) on the molecular structure and thermal properties is reported. In addition the effect of certain electrospinning processing variables such as the PAN polymer grade, the type of solvent, the temperature, the spinning voltage and the spinning distance were evaluated in terms of their effect on the resultant fibre molecular structure. The crystallinity and molecular orientation are quantified using various analytical techniques including: Fourier-Transform Infra-Red Spectroscopy (FTIR); Differential Scanning Colorimetry; (DSC) Thermal Gravimetric Analysis, TGA, Scanning and Transmission Electron Microscopy; Wide-Angle X-ray Diffractometry, XRD, Small-angle Neutron Scattering; SANS, Solid-state 13C Nuclear Magnetic Resonance Spectroscopy; NMR, and Electron-spin Resonance Spectroscopy, ESR. The researcher has ascertained in this study that the orientation of electrospun PAN is comparable to that in commercial wet-spun fibres when the electrospinning field strength is greater than 0,75 kV per cm. The process of electrospinning leads to chemical degradation of the PAN polymer only previously noted by other fibre scientists after heating PAN fibres to more than 280 C. This is due to the high mechanical stress on the high surface area electospun fibres spun into an oxygen rich air atmosphere. The addition of certain salts, particularly lithium chloride and copper nitrate, to the PAN electrospinning dope by the researchers produced fibres with improved thermal stability in comparison to the control PAN samples with no additives. In addition these salts lower the endotherm for the production of carbonized fibres from PAN fibres and will therefore make more structured, stronger, high tenacity carbon fibres. The XRD revealed that through the addition of certain salts to disrupt the dipole interations in PAN, that fibres with a 2D hexagonal crystal structure can be electrospun and have a structure similar to wet spun PAN. It is shown that fibres in a non-aligned electrospun mat have a 3D crystal structure and lower molecular orientation that wet spun fibres. Some industrial applications of electrospinning using PAN fibres are developed and reported. / AFRIKAANSE OPSOMMING: Polyakrilonitrielpolimere (PAN) is van belang weens die baie unieke eienskappe wat hulle het in vergelyking met die meeste ander vesel-vormende polimere. Die fokus van hierdie studie op die effek van verskeie veranderlikes en byvoegmiddels op hul buitengewone termiese eienskappe en interne molekulêre morfologie, met die doel om die werksverrigting van hierdie vesel in industriële toepassings te verbeter, of ten minste by te dra tot die begrip van hoe die vesel-prosesveranderlikes die termiese werksverrigting beïnvloed. Die elektrospinproses is gebruik om monsters van PAN met bymiddels te prosesseer om vas te stel wat die effek sou wees op die molekulêre oriëntering en kristalliniteit van die gelewerde nano- en mikrongrootte vesels. Verslag word gelewer oor die effek van bymiddels in die vorm van oligomere met „n lae molekulêre gewig, mengsels van geleidende polimere en verskillende nano-partikels en geleidende soute (meestal koper- en litium-gebaseerd). Die effek van sekere veranderlikes in die elektrospinproses, soos die PAN polimeer-graad, die temperatuur, die tipe oplosmiddel, die spin-spanning en spin-afstand, is geëvalueer in terme van hulle effek op die vesels wat gelewer word. Die kristalliniteit en molekulêre oriëntering word gekwantifiseer deur verskeie analitiese tegnieke te gebruik, onder meer: Fourier-Transform Infrarooispektroskopie; Differensiële Skandeerkolorimetrie; Termiese Gravimetriese Ontleding; Skandeeringelektronmikroskopie; Transmissie Elektron Mikroskopie; Wye-hoek X-straal Diffraktometrie; Klein-hoek Neutronstrooiing; Vaste-toestand 13C Kern Magnetiese Resonansiespektroskopie; en Elektronspin Resonansiespektroskopie. Dit is in hierdie studie vasgestel dat die oriëntering van elektro-gespinde PAN vergelykbaar is met kommersiële nat-gespinde vesels as die elektro-spin veldsterkte groter is as 0,75 kV per cm. Die elektro-spin proses lei tot chemiese degradasie van die PAN polimeer, wat voorheen slegs deur ander vesel-wetenskaplikes waargeneem is nadat PAN tot meer as 280 C verhit is. Dit word veroorsaak deur die hoë meganiese spanning op die hoë-oppervlakarea vesels wat in „n suurstofryke lug-atmosfeer gespin word. Die byvoeging van sekere soute, veral litiumchloried en kopernitraat, by die PAN elektro-spin spinlak (dope) deur die navorser het vesels gelewer met verbeterde termiese stabiliteit in vergelyking met die kontrole PAN-monsters sonder bymiddels. Verder verlaag hierdie soute die endoterm vir die produksie van gekarboniseerde vesels uit PAN-vesels, en dit sal daarom meer gestruktureerde, sterker koolstofvesels met hoë taaiheid lewer. X-straaldiffraksieanalise het gewys dat gewone elekrospin vesels ‟n driedimensionele struktuur het maar as gevolg van die byvoeging van sekere soute, wat die dipoolinteraksies in PAN opbreek, dat vesels wat 'n soortgelyke tweedimensionele struktuur het as dié van groot skaalse kommersiële nat-spin vesels, maklik d.m.v. die elektrospinproses berei kan word. Enkele nywerheidstoepassings van elektrospin is ontwikkel, en beskryf.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / Electrochemical behaviour of Ce, Fe, Cr,V and Mn in the presence of DTPA, EDTA, EDDS, NTA ligands were investigated by using cyclic voltammetry, a rotating disc electrode and electrochemical impedance spectroscopy for use in redox flow battery (RFB) systems. RFB is currently used for energy storage, the vanadium, which is used in most of the RFB’s, however suffers from species crossover and sluggish reactions, which limit the lifetime of the battery. These various ligands and metal complexes mentioned above where all examined to identify the suitable and favoured electrolyte that can be used for a RFB system. Kinetic parameters such as potential, limiting current, transfer coefficient, diffusion coefficients, and rate constants were studied. RDE experiments confirmed that the parameters measured by CV are similar under hydrodynamic conditions and can be used to determine the kinetic parameters of the redox couples. The use of DTPA as a ligand for complexation of Ce(IV) gave more favourable results compared to other ligand with various metal complexes used in this study [1-3]. The results of kinetic studies of Ce(IV)–DTPA complex shows promise as an electrolyte for a redox flow battery. The separation of V(IV)/(V), Fe (III)/(IV),Cr(III)/(IV),Mn (III)/(IV) and Ce(III)/(IV) with various ligands (EDTA, EDDS, NTA and DTPA) were also investigated using capillary electrophoresis. To understand the speciation of these metal complexes as used in this study and particularly the vanadium, for the reason that it has a complicated (V) oxidation state. The charge/discharge performance of all electrolytes used in this work was determined and a high voltage achieved when Ce-DTPA was used, and it is compared to that of the vanadium electrolyte currently in use. This was evaluated with systems studied previously. Therefore, Ce-DTPA will be a suitable electrolyte for redox flow battery systems.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The sungazer, Cordylus giganteus, is an endangered lizard species belonging to the family Cordylidae. It has been speculated that the function of semiochemical communication is performed by two types of skin glands, the femoral glands and the generation glands, which are also found in this family of lizards. Other skin glands and also the cloacal glands are further possible sources of semiochemicals. The investigation of these potential sources of chemical messages in C. giganteus, served as a starting point towards a better understanding of the chemical communication of lizard species belonging to the family Cordylidae. In continuation of this study the femoral gland secretion of the Cape girdled lizard, C. cordylus, was also investigated. Gas chromatography, low resolution GC-MS, GC-HR-MS, MO-TMS derivatisation and retention time comparison were used as analytical techniques in the chemical characterization of the femoral and generation gland secretions of C. giganteus and the femoral gland secretion of C. cordylus. Some compounds were not identified because of their low concentration in the secretions and/or mass spectra could not be obtained for pure compounds because of co-elution with other compounds. Compounds identified in the femoral gland secretion include the following: Carboxylic acids - saturated and unsaturated Alcohols Ketones Aldehydes - saturated and unsaturated Esters - saturated and unsaturated Hydrocarbons - saturated and unsaturated Nitriles Amides - saturated and unsaturated y-Lactones Squalene u-Tocopherol Steroids Quantitative analysis of the femoral and generation gland secretions of a number of sungazers indicated distinct differences between the secretions of males and females (in the case of the femoral gland secretions), but no apparent trend could be found in the differences between the femoral and generation gland secretions of individual lizards of the same gender. Qualitative seasonal differences were however observed in the femoral gland secretions of all individuals of C giganteus. / AFRIKAANSE OPSOMMING: Die ouvolk, Cordylus giganteus, is 'n bedreigde akkedisspesie van die familie Cordilidae. Daar is gespekuleer dat twee soorte velkliere wat by hierdie familie akkedisse voorkom, naamlik die femorale- en generasiekliere, betrokke is by semiochemiese kommunikasie van hierdie diere. Ander velkliere, asook die kliere in die akkedisse se kloaka, is ook potensiele bronne van semiochemiese verbindings. Die bestudering van hierdie potensiele bronne van chemiese boodskappe by C. giganteus is as 'n beginpunt gebruik om die semiochemiese kommunikasie van die akkedisse van die familie Cordilidae beter te verstaan. Ter uitbreiding van hierdie studie is die femorale klierafskeiding van die Kaapse gordelakkedis, C. cordylus, ook ondersoek. Die femorale en generasieklierafskeidings van C. giganteus en die femorale klierafskeidings van C. cordylus is chemies gekarakteriseer deur van analitiese tegnieke, naamlik gaschromatografie, lae resolusie GC-MS, GC-HR-MS, MO- TMS derivatisering en retensietydvergelyking, gebruik te maak. Talle verbindings is nie geidentifiseer nie omdat hulle in 'n baie lae konsentrasie in die afskeidings voorkom, en/of saam met ander komponente elueer, wat veroorsaak dat daar nie massaspektra vir hierdie suiwer komponente verkry kon word nie. Verbindingstipes wat in die afskeidings voorkom, sluit die volgende in: Karboksielsure - versadig en onversadig Alkohole Ketone Aldehiede - versadig en onversadig Esters - versadig en onversadig Koolwaterstowwe - versadig en onversadig Nitriele Amiede - versadig en onversadig y-Laktone Skwaleen a-Tocopherol Steroiede Kwantitatiewe analises van die femorale en generasieklierafskeidings van verskeie ouvolk akkedisse het getoon dat daar duidelike kwantitatiewe verskille tussen die afskeidings van mannetjies en wyfies is (in die geval van die femorale klierafskeidings), maar dat daar geen duidelike patroon in die verskille tussen die femorale en generasieklierafskeidings van individuele akkedisse van dieselfde geslag is rue. Daar is kwalitatiewe seisoenale verskille tussen die femorale klierafskeidings van individue van C. giganteus gevind.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The present study deals in the first instance with the improvement of current analytical techniques for the analysis of the non-volatile content of wines. An improved sample preparation method, using solid phase extraction (SPE), was initially developed for the analysis of organic acids, sugars and phenolic compounds. Consequently, modem analytical methodologies were assessed to obtain optimal techniques for the separation of various non-volatile compounds. A capillary electrophoresis (CE) method, demonstrably more reliable than currently used high performance liquid chromatography (HPLC) and CE methods, is proposed for the analysis of organic acids. HPLC with refractive index (RI) or evaporative light scattering detection (ELSD) proved more suitable than CE for the analysis of sugars in dry wines. Liquid-chromatography-mass spectroscopy (LC-MS) offered superior sensitivity and resolution compared to the relatively new technique of CE-MS for the analysis of wine phenolics. LC-MS was further applied for the efficient and sensitive analysis of non-coloured phenolics and anthocyanins in wine. Negative- and positive electrospray ionisation, respectively, were used in conjunction with an ion-trap mass analyzer, for the identification of 34 phenolics and 31 anthocyanins in red wine samples. Complementary CE and LC methods were developed to allow the identification of artificial dyes in red wines, added illegally to improve their colour. Also, the application of stir bar sorptive extraction (SBSE) with liquid desorption and micellar electrokinetic chromatography (MEKC) for the analysis of bitter acids in beer is reported. In the second part of the thesis, the analytical results obtained for South African red and white wines were evaluated. Following comparison of the results with literature reports, several pattern recognition techniques were employed. A classification function obtained by linear discriminant analysis (LDA) was used to classify both red and white wines according to variety, based on their chemical composition. This classification is achieved independent of the factors of wine age or geographical origin, making it useful for authenticity evaluation. / AFRIKAANSE OPSOMMING: Hierdie studie het as primêre doel die verbetering van bestaande analitiese metodes vir die analise van nie-vlugtige komponente in wyn. In die lig hiervan, is eerstens 'n toepaslike monster-voorbereidingstegniek, gebasseer op soliede fase ekstraksie (SPE), ontwikkel vir die gelyktydige analise van organise sure, suikers en fenoliese komponente vanuit die wyn matriks. Vervolgens is moderne analitiese rtietodes ondersoek en gepastde skeidingstegnieke is ontwikkel vir die verskillende chemiese wyn-komponente. Kappillêre elektroforese (CE) en hoë-druk vloeistof-chromatografie (HPLC) in kombinasie met verskeie deteksie-metodes is vergelyk. Hieruit is 'n verbeterde CE metode vir die analise van organise sure is ontwikkel, terwyl HPLC in kombinasie met refraksie-indeks- en verdampings lig verstrooiings deteksie (ELSD) die beste resultate lewer vir die analise van suikers in droë wyne. Die toepasbaarheid van vloeistof-chromatografie met massa spektrometriese deteksie (LC-MS) vir die analise van fenoliese komponente is gedemonstreer, terwyl CE-MS onvoldoende resolusie en sensitiwiteit toon vir die analises. LC-MS is vervolgens ook gebruik vir die identifikasie van 34 fenoliese verbindings en 31 antosianiede in rooi wyn. Komplementêre HPLC en CE metodes is ontwikkel vir die identifikasie van onwettige sintetiese kleurstowwe in' rooi wyn. 'n Addisionele monstervoorbereidingsstap, roerstaaf sorptiewe ekstraksie (SBSE), is saam met vloeistof-desorpsie en misellêre elektrokinetiese chromatografie (MEKC) gebruik vir die analise van hops bitter sure in bier. In die tweede deel van die tesis word die resultate verkry m.b.v. bg. tegnieke vir die analise van Suid-Afrikaanse rooi- en wit wyne, bespreek. Die resultate is vergelyk met waardes uit die literatuur, en verskeie statistiese metodes is gebruik om die data te ondersoek. Met behulp van chemometriese metodes is 'n klassifikasie funksie verkry wat die klassifikasie van Suid-Afrikaanse wyne volgens druifsoort, gebasseer op die chemiese samestelling van die wyne, toelaat. Die klassifikasie is moontlik, onafhanklik van die ouderdom of geografiese oorsprong van die wyne.

Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The black wildebeest, Connochaetes gnou, is a terriorial animal and although it is not generally accepted, it is believed that it defines its territory by scent marking, using interdigital and preorbital secretions, faeces, and urine. The aim of this study was to characterize the chemical constituents of the interdigital secretion. Due to the complexity of the secretion, only one hundred and ten of the approximately 350 compounds could be determined with known techniques. Gas chromatography, low resolution GC-MS and retention-time comparison were the main analytical techniques used. Classes of compounds identified in the interdigital secretion include the following: • Hydrocarbons - Aliphatic (saturated and unsaturated) and aromatic • Alcohols - Aliphatic (saturated, unsaturated, cyclic and diols) • Phenols and Phenylalkanols • Aldehydes - Aliphatic (saturated and unsaturated) and aromatic • Ketones - Aliphatic (saturated, unsaturated, cyclic and diketones) and aromatic • Hydroxy ketones - Aliphatic and cyclic • Carboxylic acids - Aliphatic (saturated, unsaturated and cyclic) and aromatic • An anhydride • Esters - Methyl esters, ethyl and higher esters, unsaturated esters and aromatic esters • Lactams • A steroid Only small qualitative and quantitative differences were found between the male and female interdigital secretions. / AFRIKAANSE OPSOMMING: Die swartwildebees, Connochaetes gnou, is 'n territoriale dier en alhoewel dit nie algemeen aanvaar word nie, word vermoed dat hierdie bokke hul gebied afbaken met behulp van interdigitale en preorbitale afskeidings, en deur faeces en urine. Die doel van hierdie studie was om die chemiese samestelling van die interdigitale afskeiding te karakteriseer. As gevolg van die kompleksiteit van die afskeiding, kon slegs eenhonderd-en-tien van die ongeveer 350 verbindings met bekende bestaande tegnieke geïdentifiseer word. Gaschromatografie, lae resolusie GC-MS en retensietyd-vergelyking was die belangrikste analitiese tegnieke wat gebruik is. Klasse van verbindings wat bepaal is, sluit die volgende in: • Koolwaterstowwe - Alifaties (versadig en onversadig) en aromaties • Alkohole - Alifaties (versadig, onversadig, siklies en diole) • Fenole en Fenielalkanole • Aldehiede - Alifaties (versadig en onversadig) en aromaties • Ketone - Alifaties (versadig, onversadig, siklies en diketone) en aromaties • Hidroksiketone - Alifaties en siklies • Karboksielsure - Alifaties (versadig, onversadig en siklies) en aromaties • 'n Anhidried • Esters - Metiel esters, etiel en hoër esters, onversadigde esters en aromatiese esters • Laktame • 'n Steroïed Slegs klein kwalitatiewe en kwantitatiewe verskille is gevind tussen die bul en koei interdigitale afskeidings.

Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The aim of this thesis is to use tin-mediated reactions to differentiate between the four zones in the myo-inositol ring that consists of five contiguous equatorial and one axial hydroxyl groups. It is expected to give chemical control over the hexitol that can be put to good use in commercializing the phosphate derivatives of myo-inositol that are of pharmaceutical value. As point of departure 1,2-0-cyclohexylidene-myo-inositol (II.I) was synthesized that contains a tetrol with one end adjacent to an axial acetal oxygen and the other end adjacent to an equatorial acetal oxygen. The selective protection of position 3 (Dmyo- inositol) was investigated. Various problems lead to the selective silylation of the acetal at position 5. The silane forms the basis of the subsequent investigation because the cyclitol is now divided into an isolated mono-ol and a trans-diol allowing for easier differentiation between the various hydroxyl groups. It was indeed possible to differentiate the trans-diol from the mono-ol by using carbonylation and allylidenation. Ring closure occurs in both cases. In the carbonylation case the resultant five-membered ring is less stable than that of the allylidene due to the Sp² hybridized carbon atom of the carbonate compared to theSp³ hybridized carbon of the allylidene group. Preliminary work was done on the racerrue 1,2-0-cyclohexylidene-myo-inositol (II.VII) in order to use the acquired technology on the chiral camphor analog. The transition from racemic to chiral proved problematic since the camphor acetal is difficult to prepare and its selective silylation differs from that observed for cyc1ohexylidene. The camphor acetal itself was silylated in the process. (S)-( -)-Camphanic chloride was therefore used as chiral auxiliary in the protection of position six of the racemic 1,2,3,4,5-protected myo-inositol, thus solving the problems encountered in the protection of position six whilst combining the protection and chiral induction steps. The resultant diastereomers could both be used in the synthesis of IP₃ and IP₄ respectively, eliminating the disposal of half ofthe product. This project lead to the development of useful chiral differentially protected myoinositol derivatives, which could be useful in synthesis of various other myo-inositol derivatives. Besides the synthesis of useful chiral differentially protected myo-inositol derivatives, this investigation developed new applications in the tin-mediated derivatization of sugars. The following compounds were synthesized during this investigation. Bold numbers indicates novel compounds. / AFRIKAANSE OPSOMMING: Die doel van hierdie proefskrif is om met behulp van tin-bemiddelde reaksies onderskeid te maak tussen die vier sones in die mia-inositolring, wat bestaan uit vyf aaneenlopende ekwatoriale hidroksigroepe en een aksiale hidroksigroep. Die verwagting was om vinnig, effektiewe chemiese beheer oor die genoemde heksitol te verkry om sodoende chemies en kommersiëel munt te slaan uit die farmaseutiese werking van die fosfaatafgeleides van mia-inositol. As eerste uitgangspunt is 1,2-0-sikloheksilideen-mia-inositol (II.I) berei, wat lei tot die vorming van 'n tetrol waarvan die een punt naasliggend aan 'n aksiale asetaalsuurstofatoom en die ander punt naasliggend aan 'n ekwatoriale asetaalsuurstof is. As voortsetting is die selektiewe beskerming van posisie 3 (D-mia-inositol) ondersoek. Velerlei probleme lei tot die selektiewe sililering van die asetaal by posisie 5 (II.VII). Die silieleter vorm die basis van al die daaropvolgende ondersoeke omdat dit die siklitol in 'n trans-diol en 'n geïsoleerde mono-ol verdeel en die verskillende hidroksigroepe daarvan makliker van mekaar onderskei kan word. Dit is inderdaad moontlik om die trans-diol van die mono-ol te onderskei deur karbonilering of allilidenering. In albei gevalle vind ringannulering plaas. In die geval van die karbonilering is die gevormde vyflidring minder stabiel as wat die geval is vir die allilideengroep. Die rede hiervoor is dat die karbonaatkoolstofatoom Sp²- gehibridiseer is terwyl die ooreenstemmende koolstofatoom van die allilideen Sp³- gehibridiseer is. Ontwikkelingswerk is op die rasemiese 1,2-0-sikloheksilideen-mia-inositol (II.VII) gedoen ten einde dit op die chirale kamferasetaalanaloog toe te pas. Die oorgang van rasemies na chiraal is egter problematies aangesien die kamferasetaal moeiliker vorm en selfs as dit vorm toon die reaksies, soos byvoorbeeld die sililering, ander selektiwiteit as wat die geval is vir die rasemiese mengsel. Sililering van die kamferasetaallei tot sililering van die kamfer self. (S)-(-)-kamfanoïelchloried is gevolglik as chirale hulpreagens gebruik om posisie 6 van die rasemiese 1,2,3,4,5-beskermde-mia-inositol te beskerm. Hierdie benadering los die problematiek rondom die beskerming van posisie 6 sowel as die induksie van chiraliteit op. Die twee diastereomere wat op hierdie wyse vorm, kan albei in die sintese van onderskeidelik IP₃ en IP₄ gebruik word, wat die verlies aan helfte van die produk verhoed. Behalwe die daarstelling van bruikbare chirale differensiëel-beskermde mioinositolafgeleides wat gebruik kan word om 'n verskeidenheid chirale mioinositolafgeleides te berei, het hierdie ondersoek nuwe toepassings in tin-bemiddelde derivatisering van suikers daargestel. Die volgende verbindings is gedurende die verloop van hierdie ondersoek gesintetiseer, waar verbindings vir die eerste keer gesintetiseer is word dit aangedui deur die verbinding se nommer vet (bold) te druk.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Due to the adverse human health effects associated with mercury (Hg) toxicity, an innovative method for inorganic mercury (Hg2+) determination in aqueous solutions was investigated. The method of Hg2+ determination involved the use of a Hg2+ selective chemosensor immobilised onto an indium tin oxide (ITO) coated electrode in a photoelectrochemical cell. Upon light activation and in the presence of Hg2+ the fluorescent chemosensor absorbed a photon, and charge separation would occur according to the nature of the semiconductive material coated onto the ITO substrate. The charge separators and semiconductors investigated were an n-type carrier TiO2, polyaniline (PANI) and copolymers of polyaniline and 2-bromoaniline (P[A-co-2- BrA]s) with different monomer ratios. The polymer and copolymer coated ITO working electrodes used in the Hg2+ sensitive photoelectrochemical cell were electrochemically evaluated. The results demonstrated that the ITO coated with PANI had superior conductive and semiconductive properties compared to ITO coated with P[A-co-2-BrA]s. The ITO glass substrates were coated with TiO2, PANI or P[A-co-2-BrA]s, followed by the fluorescent chemosensor, a rhodamine 6G derivative (RS). The electrodes were subsequently photoelectrochemically evaluated in a photoelectrochemical cell in the presence of Hg2+. The PANI-RS coated electrode behaved as a photocathode in the presence of Hg2+ under illumination. The PANI-RS photoresponse increased with increasing Hg2+ concentration in the range 10 to 150 μg L-1, with a limit of detection of 6 μg L-1. ITO coated with TiO2 (ITO/TiO2) followed by a composite of PANI and RS had a linear photoanodic response in the Hg2+ concentration range of 10 to 200 μg L-1 and a limit of detection of 5 μg L-1. ITO and ITO/TiO2 coated with the P[A-co-2-BrA]s and RS had considerably lower photoresponses towards Hg2+ in aqueous solutions compared to PANI-RS. The photoresponses decreased with increasing 2-bromoaniline content. The PANI and P[A-co-2-BrA]s coated ITO and ITO/TiO2 electrodes were then also coated with another rhodamine 6G derivative with a thiolactone moiety (RT). The PANI coated electrode yielded a photocathodic response in the Hg2+ concentration range 0.2 to 5 μg L-1. ITO coated with TiO2 had no photoresponse towards Hg2+ due to repulsive forces between TiO2 and the RT molecules. The photoresponses of the working photoelectrodes towards Hg2+ were further evaluated in a custom photoelectrochemical Hg2+ detector. The photoresponses of PANI-RS and PANI-RT gave qualitative results for the presence of Hg2+ in aqueous solutions in concentrations as low as 2 μg L-1. / AFRIKAANSE OPSOMMING: Weens die negatiewe gesondheids aspekte toegeskryf aan Hg2+ vergiftiging is ‘n nuwe innoveerende metode van Hg2+ deteksie in wateroplossings ondersoek. Die voorgestelde metode van Hg2+ deteksie behels die gebruik van ‘n Hg2+ selektiewe chemosensor geimmobiliseer op ITO elektrodes in ‘n fotoelektrochemiese sel. Met lig aktivering en in die teenwoordigheid van Hg2+, absorbeer die fluoreseerende chemosensor ‘n foton, gevolg deur lading skeiding, soos bepaal deur die aard van die halfgeleidende material wat op die ITO platjies bedek is. Die halfgeleiers wat ondersoek was, was TiO2, PANI en ko-polimere van PANI met 2-bromoanilien. Die polimeer en kopolimeer bedekte ITO werkende elektrodes wat in die Hg2+ sensitiewe fotoelektrochemiese sel gebruik is, is elektrochemies geevalueer. Daaruit is gevind dat ITO bedek met PANI superieure geleier en halfgeleier eienskappe het in vergelyking met die ITO wat bedek is met P[A-co-2-BrA] kopolimere. Die ITO glas plaatjies is bedek met TiO2, PANI en die P[A-co-2-BrA] kopolimere gevolg deur die fluoresseerende chemosensor, RS. Die elektrodes is onderskeidelik fotoelektrochemies getoets in ‘n fotoelektrochemiese sel in die teenwoordigheid van Hg2+. Die PANI-RS elektrode het soos ‘n fotokatode opgetree in die teewoordigheid van Hg2+ onder beligting. Die foto-reaksie van die PANI-RS elektrode teeonoor Hg2+ het liniêr toegeneem van 10 μg L-1 tot 150 μg.L-1 met ‘n limiet van deteksie op 6 μg L-1. ITO/TiO2 wat bedek is met ‘n samestelling van PANI en RS het ‘n fotoanodiese reaksie gehad teenoor Hg2+ in die liniêre reeks van 10 tot 200 μg L-1 met ‘n deteksie limiet van 5 μg L-1. ITO en ITO/TiO2 bedek met die P[A-co-2-BrA] kopolimere het heelwat laer fotoreaksies getoon teenoor Hg2+ in waterige oplossings Die fotoreaksie het afgeneem met toeneemende 2-bromoanilien inhoud van die kopolimeer. Die PANI en P[A-co-2-BrA] kopolimere bedekte ITO en ITO/TiO2 elektrodes is verder bedek met ‘n tweede rhodamine 6G afgeleide, RT. Die ITO/PANI bedek met RT het weer ‘n fotokatodiese reaksie gehad teenoor Hg2+ in die konsentrasie interval 0.2 tot 5 μg L-1. Die ITO/TiO2 elektrode bedek met die PANI-RT samestelling het geen fotoreaksie gehad teenoor Hg2+ weens afstotende kragte tussen die TiO2 and RT molekules. Die fotoreaksies van die verskeie werkende elektrodes teenoor Hg2+ is verder getoets in ‘n tuisgemaakte fotoelektrochemiese Hg2+ detektor. Die fotoreaksies van die PANIRS en PANI-RT samestellings op ITO het kwalitatiewe resultate gelewer vir die teenwoordigheid van Hg2+ in waterige oplossings in konsentrasies tot so laag soos 2 μg L-1.