M.Sc. / The disinfection of drinking water is an important step in the water treatment process. However, toxic (unwanted) disinfection by-products (DBPs) are often produced during the disinfection of drinking water. One such group of DBPs are the nitrosamines such as N-Nitrosodimethylamine (NDMA). Nitrosamines, particularly NDMA, are highly carcinogenic, mutagenic and teratogenic. The US Environmental Protection Agency (USEPA) placed these compounds into the group B2, which indicates compounds of probable human carcinogens. The USEPA integrated risk information system (IRIS) database lists an estimated 10-6 lifetime cancer risk level for NDMA in drinking water of 0.7 ng/L. The formation of NDMA during drinking water disinfection, particularly chloramination, has been linked to the formation of NDMA through a reaction between monochloramine and organic nitrogen precursors via unsymmetrical dialkylhydrazine intermediates, such as unsymmetrical dimethylhydrazine (UDMH). UDMH is oxidized by dissolved oxygen to form NDMA. Therefore, it is also crucial to remove NDMA precursors (UDMH and dimethylamine (DMA)), before disinfection is carried out. Also, the chlorination of secondary wastewater can result in the formation of NDMA. In this research project, determination of nitrosamines, especially NDMA was done at four different water treatment plants in South Africa. Water samples collected from Midvaal, Sedibeng, Magalies (Vaalkop and Klipdrift) and Rand Water treatment plants were qualitatively analysed for the presence of NDMA. Also, the determination of possible NDMA precursors such as dimethylamine and UDMH was investigated in water samples collected from Sedibeng water treatment plant. The water samples were collected before and after each drinking water treatment process (coagulation, sedimentation, filtration, chlorination and chloramination or ozonation). Solid phase microextraction (SPME) was employed in the extraction of the water samples. Polydimethylsiloxane/divinylbenzene (PDMS/DVB) proved to be the most efficient fibre for the SPME extraction procedure. The water samples vi were then qualitatively analysed using gas chromatography-mass spectrometry (GC-MS). Very small amounts of NDMA were detected in water samples collected from Sedibeng water treatment plant. There was no detectable presence of NDMA or other nitrosamines in water samples collected from the other treatment plants. Water-insoluble cyclodextrin (CD) polyurethanes were then used to ascertain how much of the NDMA they would remove. The CD polymers showed capacity to remove NDMA and dimethylamine (which is a known NDMA precursor) in the water samples with 80% removal efficiency for NDMA (when comparing peak area before and after treatment with CD polymers) and approximately 98% removal rate for DMA.

M.Sc. / Safe drinking water is an essential resource for human survival, health, dignity and development. However, this vital resource has become scarce mainly due to population growth, economic activity, climate change and pollution. Treatment of polluted water is expensive and does not always ensure delivery of safe drinking water to humans. Reports on the detection of pollutants such as organics, bacteria, inorganics and the occurrence of toxic disinfection byproducts in treated water in distribution systems have necessitated further research in improving water treatment methods. Metal impregnated carbon nanotube incorporated into cyclodextrin polyurethanes were synthesised by first functionalising carbon nanotubes and then impregnating them with metal nanoparticles. The resultant product was confirmed using Transmission electron microscopy (TEM). The metal nanoparticles were found to have a diameter range of 6 to 35 nm. The metal impregnated carbon nanotubes were then polymerised to produce cyclodextrin polyurethanes. The polymers were characterised using various techniques such as Scanning electron microscopy (SEM), Emission dispersive X-ray spectrometry (EDX) and Brunauer-Emmet-Teller analysis. The metal nanoparticles were found to be part of the polymers through EDX and the polymers’ surface areas were measured to be 0.78 and 0.3383 m2/g for silver and copper polymers, respectively. The synthesised polymers were tested for their efficacy at destroying pathogenic bacteria from water. The polymers were found to inactivate bacteria by up to 4 logs from spiked water samples. These metal impregnated polymers when compared to native carbon nanotubes and cyclodextrin polymers had an enhanced antibacterial property. In environmental samples, metal impregnated polymers destroyed up to 3 logs of bacteria. There was complete removal of bacteria from filtered environmental water samples. Factors affecting the polymers’ efficacy were turbidity, nature of sample and the ratio of bacterial cells removed per gram of polymer.

The contamination of water by organic compounds has resulted in an escalation in research efforts to combat this problem. These organics can be harmful to human health and the environment in general, and they pose unique challenges to several industrial applications. Even when present at very low concentrations, they tend to bioaccumulate and interact with endocrine systems. However, due to the chemical nature of these compounds, current technologies are still challenged to effect their removal from water. Of currently used technologies, activated carbon and reverse osmosis can remove most of the organic pollutants but fail to remove them to very low concentrations (ng/L levels). Recent studies have explored the capabilities of nanoporous cyclodextrin (CD) polymers, a class of nanomaterials that show great potential to absorb organic contaminants from water. The project reported in this dissertation was undertaken to further explore the efficacy of these polymers in order to assist industries and municipalities in their quest to solve the problem of water contamination by organic species. The ability of these polymers to remove selected organic contaminants from water at varying concentrations was studied. The investigated pollutants were chlorinated disinfection by-products (DBPs), taste and odour causing compounds (geosmin and 2-methylisoborneol) and humic acid, which was used to mimic natural organic matter (NOM). Water samples were pre-concentrated using solid phase extraction (SPE) and subsequently quantified by Gas Chromatography-Mass Spectrometry (GC/MS). The CD polymers demonstrated absolute efficiency at quenching organics at very low concentrations compared to granular activated carbon (GAC). The recyclability efficiency of the CD polymers was also investigated. Most of the work was carried out using rapid small scale column tests (RSSCTs) that were designed in our laboratories. The general design of the study and pathway that was followed while conducting these experiments is shown in the flow diagram on the next page. / Dr. B.B. Mamba

Orientador: Francisco Benedito Teixeira Pessine / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T11:44:21Z (GMT). No. of bitstreams: 1 Calderini_Adriana_M.pdf: 3626167 bytes, checksum: 65a0e866a04669d0055a59e424f4d2c5 (MD5) Previous issue date: 2006 / Mestrado / Físico-Química / Mestre em Química

Luminescence sensors based on LED were prepared by modification of LED poly- carbonate surface and following binding of luminescence dyes on this surface. Two methods of modification were utilized. The first one was the oxidation of the surface yielding free carboxylic groups. Such modified LEDs were then covered by cationic cresyl violet dye. The second modification consisted of nitration and consequent reduction to free amino groups followed by binding of anionic sulforhodamine dye. The stability of emission and the stability of dye binding were studied. Then, the response of constructed sensors to toluene as analyte in gas and liquid phase was measured.

Thirty Bacteroides strains from the human colon were tested for ability to degrade cyclodextrins (CD). Twenty four strains were able to degrade CD. Cyclodextrinase in two of these strains B. ovatus 3524 and B. distasonis Cl8-7 has been studied. Organisms were grown on a minimal medium containing CD (0.5%), and cyclodextrinase activity was assayed by measuring the increase in reducing sugar (as glucose) when CD was incubated at 37℃ for 4 h with crude enzyme preparations. Cyclodextrinase activity was predominantly cell bound and induced in both organisms by growth on CD. Analysis via high performance liquid chromatography showed that products of CD hydrolysis by the crude enzyme preparations from the 2 strains were sharply different. B. ovatus 3524 cyclodextrinase yielded glucose only, while the B. distasonis Cl8-7 enzyme catalyzed production of a series of maltooligomers. Cyclodextrinase of both strains was stable at 4℃ for at least 48 h. B. distasonis Cl8-7 cyclodextrinase showed greater than 75% retention of activity at temperatures up to 55℃ after 48 h, whereas the B. ovatus 3524 enzyme was labile above 25℃. Optimum activity and stability of cyclodextrinase from both strains occured at pH 7.0. Salt precipitation and chromatographic methods were utilized in an attempt to purify the enzyme(s) in crude cyclodextrinase. No enzymes were purified to homogeneity, but a 15- to 17-fold increase in specific cyclodextrinase activity was obtained via hydrophobic interaction chromatography. Also, the products obtained by the action of cyclodextrinase from B. ovatus 3524 were markedly altered during purification, suggesting that the crude cyclodextrinase contains a mixture of enzymes. / M.S.

"December 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 221-233) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The first three, pure, single-isomer, 6-O-sulfo a-cyclodextrins, the sodium salts of hexakis(6-O-sulfo)-a-CD (HxS), hexakis(2,3-di-O-methyl-6-O-sulfo)-a-cyclodextrin (HxDMS) and hexakis(2,3-di-O-acetyl-6-O-sulfo)-a-cyclodextrin (HxDAS) have been synthesized, analytically characterized and utilized as chiral resolving agents in capillary electrophoresis. The purity of each synthetic intermediate and of the final product was determined by HPLC-ELSD and indirect UV-detection capillary electrophoresis. The structural identity of each intermediate and final product was verified by 1D and 2D NMR, and mass spectrometry.HxS, HxDMS and HxDAS have been used to separate a series of neutral, basic, ampholytic and acidic enantiomers in pH 2.5 and pH 9.5 aqueous and acidic methanol background electrolytes using capillary electrophoresis. Rapid separations with satisfactory peak resolution values were obtained for most of the analytes, indicating that HxS, HxDAS and HxDMS can serve as chiral resolving agent for a wide range of analytes. The observed separation patterns follow the predictions of the CHArged Resolving agent Migration (CHARM) model. The separation patterns observed with HxS, HxDAS and HxDMS as chiral resolving agent were compared with those of (1) b-cyclodextrin analogues, such as, heptakis(6-O-sulfo)-b-cyclodextrin (HS), heptakis(2,3-di-O-acetyl-6-O-sulfo)-b-cyclodextrin (HDAS) and heptakis(2,3-di-O-methyl-6-O-sulfo)-b-cyclodextrin (HDMS); (2) g-cyclodextrin analogues, such as, octakis(6-O-sulfo)-g-cyclodextrin (OS), octakis(2,3-di-O-acetyl-6-Osulfo)- g-cyclodextrin (ODAS) and octakis(2,3-di-O-methyl-6-O-sulfo)-g-cyclodextrin (ODMS). The effects of the structure of the analytes, and those of the pH and the solvent of the background electrolyte were also studied.

The first three, pure, single-isomer, 6-O-sulfo a-cyclodextrins, the sodium salts of hexakis(6-O-sulfo)-a-CD (HxS), hexakis(2,3-di-O-methyl-6-O-sulfo)-a-cyclodextrin (HxDMS) and hexakis(2,3-di-O-acetyl-6-O-sulfo)-a-cyclodextrin (HxDAS) have been synthesized, analytically characterized and utilized as chiral resolving agents in capillary electrophoresis. The purity of each synthetic intermediate and of the final product was determined by HPLC-ELSD and indirect UV-detection capillary electrophoresis. The structural identity of each intermediate and final product was verified by 1D and 2D NMR, and mass spectrometry.HxS, HxDMS and HxDAS have been used to separate a series of neutral, basic, ampholytic and acidic enantiomers in pH 2.5 and pH 9.5 aqueous and acidic methanol background electrolytes using capillary electrophoresis. Rapid separations with satisfactory peak resolution values were obtained for most of the analytes, indicating that HxS, HxDAS and HxDMS can serve as chiral resolving agent for a wide range of analytes. The observed separation patterns follow the predictions of the CHArged Resolving agent Migration (CHARM) model. The separation patterns observed with HxS, HxDAS and HxDMS as chiral resolving agent were compared with those of (1) b-cyclodextrin analogues, such as, heptakis(6-O-sulfo)-b-cyclodextrin (HS), heptakis(2,3-di-O-acetyl-6-O-sulfo)-b-cyclodextrin (HDAS) and heptakis(2,3-di-O-methyl-6-O-sulfo)-b-cyclodextrin (HDMS); (2) g-cyclodextrin analogues, such as, octakis(6-O-sulfo)-g-cyclodextrin (OS), octakis(2,3-di-O-acetyl-6-Osulfo)- g-cyclodextrin (ODAS) and octakis(2,3-di-O-methyl-6-O-sulfo)-g-cyclodextrin (ODMS). The effects of the structure of the analytes, and those of the pH and the solvent of the background electrolyte were also studied.

Cyclodextrins (CDs) are cyclic oligosaccharides of various sizes containing several α-(1→4)-linked D-(+)- glucopyranose units. The commercially available ones comprise six, seven or eight glucose units, named respectively α-CD, β-CD and γ-CD. Their truncated cone-like and well-defined cavity are particularly attractive for the encapsulation of a variety of substrates. As such, they found numerous applications in many areas of chemistry. A recent development, from which the present work is inspired, consisted in covalently linking transition metals to CD cavities in order to perform and study catalytic reactions in a confined environment featuring steric repulsive or attractive noncovalent interactions with the substrate or/and the metal coordination sphere.The first part of this thesis focuses on reviewing transition metal-based cavitands, for which the first and second metal coordination spheres are controlled by their cavity-shaped ligand. The following chapters are concerned with the synthesis, coordination and catalytic properties of two new phosphane ligands built on a large β-CD scaffold. The first one, named WIDEPHOS, is a diphosphine having two phenylphosphinidene "PPh" units capping adjacent glucose units on a methylated β-CD. This ligand features two phosphorus lone pairs pointing to the cavity interior but not aligned. These geometrical features, combined with the large distance separating the two phosphorus atoms, promote the formation of "imperfect" trans-chelate complexes in which the metal centre swings about the ligand. This unprecedented molecular movement, christened "oschelation", allows each phosphorus atom to form an optimal bond in turn with the coordinated d8 and d10 transition metal ions. Further studies on WIDEPHOS proved that it is better suited for coordinating dinuclear fragments within the confinement of the large β-CD cavity. Severe steric constrains on the metal first sphere of coordination result in the formation of single μ-chlorido bridged dinuclear species. In this new type of square planar complexes, non-optimal orbital overlapping measured by the so-called tilt angle was also found to take place for one of the phosphorus atom together with an "oschelation" movement involving non identical donor atoms, namely a phosphorus and an oxygen atom. Static gold(I) dinuclear complexes displaying similar imperfect orbital overlapping for one of the phosphorus atom were also prepared.