There is currently no published method for the analysis of the herbicide quizalofop-p-tefuryl or its matabolite quizalofop in biological matrices. Quizalofp-p-tefuryl is a relatively new herbicide with apparent low toxicity and is readily degraded. Its metabolite also has herbicide activity. Quizalofop-p-tefuryl is a aryloxyphenoxypropionate and is a post emergence herbicide used for pulses and vegetables. This work reports on a method for the analyses of this pesticide residue and its metabolite in soybean using HPLC on a C-18 column with UV detection at 332 nm. Several methods are tried including some involving the use of solid phase extractors like silica, Florisil and strong cationic exchange cartridges. The main method developed uses an extraction solvent hexane: acetone: acetic acid for extracting the quizalofop-p-tefuryl and quizalofop from the ground soybean. The extracts are then made alkaline with NaOH and this deprotonates the quizalofop separating it from the hexane phase which contains the quizalofop-p-tefuryl. The hexane phase is extracted with ACN and quizalofop-p-tefuryl partitions into this phase. The quizalof-p-tefuryl is repartitioned into a fresh diethyl ether: hexane phase by adding a large quantity of H2O and NaCL to the ACN layer. The organic phase is washed and evaporated to dryness before being made up to volume with ACN for direct analysis by UV detection or by derivatising it to methoxychloroquinoxaline for fluorescence detection. Using the method that directly detects the analytes, for quizalofop-p-tefuryl and quizalofop at spike levels, the method has average recoveries. The precision of recoveries for both compounds is about 9%. The method is fairly robust. Time of analysis per analyte is about 2 hrs. / Master of Science

The goals of this research were first to examine flame quenching in tubing smaller than the quench diameter, and then to place lower size limits on microcombustor and microreactor systems by studying a catalytic microcombustor burning propane. In the first set of experiments, flame quenching was examined as a function of wall temperature for various hydrocarbon fuels. This was accomplished by creating a wall temperature profile along a tube, allowing a flame to propagate down the tube, and measuring the temperature of the tube wall coincident with the flame front. This wall quench temperature was plotted as a function of both the equivalence ratio and tube diameter. Fuels tested included propane, hexane, kerosene and diesel. Results showed that quench diameter was reduced by elevating the wall temperature and that the quench temperature increased for increasing mixture flow velocities. Flames were produced in tubes down to 0.8 mm in diameter. In the second set of experiments, a catalyst was used in combination with fuel preheating to obtain a self-sustaining combustion reaction in a chamber approximately 0.25 mm³ in size. Propane was used in this experiment. Results demonstrated that a stable self-sustaining reaction can be obtained in the microscale regime and that reaction temperatures are on the order of 900°C. This research not only aided in the characterization of hydrocarbon combustion in small diameter channels but also showed promise for development of microcombustor systems. / Graduation date: 2002

Tuberculosis (TB) is the disease arising from infection by Mycobacterial tuberculosis and kills millions of people every year. Difficulties in the treatment of TB and the emergence of multiple-drug resistant and extreme-drug resistant M. tuberculosis strains have increased interest in finding new antimycobacterial agents. The cell wall of mycobacteria is essential for the survival of these bacteria and enzymes involved in its assembly are key targets for anti-mycobacterial chemotherapy. One of the largest components of the cell wall is the arabinogalactan, which is composed of arabinofuranose (Araf) and galactofuranose (Galf) residues. These monosaccharides are incorporated into the polysaccharide by arabinosyltransferases and galactosyltransferases that employ decaprenolphophoarabinose (DPA) and uridine diphospho-galactofuranose (UDP-Galf) as the donor substrate, respectively. The synthesis of analogues of DPA and UDP-Galf as potential inhibitors of mycobacterial glycosyltransferases is presented in the thesis. Carbohydrate mimics of Araf and Galf that have a bicyclo[3.1.0]hexane at the core were prepared. Key steps involved the formation of bicyclo[3.1.0]hexane system via an intramolecular displacement reaction followed by a separation by converting a mixture of enantiomers into diastereomers. The absolute configuration of these species was confirmed by X-ray analysis of a crystalline derivative of the Araf analogue. The bicyclo[3.1.0]hexane based mimics were then alkylated with various aldehydes through reductive amination to form the DPA and UDP-Galf analogues. The synthesis of the sulfonium ion analogs of Galf was also carried out. The precursor of these compounds, a cyclic sulfide, was synthesized in nine steps from D-arabinitol. The key step is a conversion of an olefin into hydroxymethyl group thus establishing a stereogenic centre that is essential in forming a molecule that is a mimic of the galactofuranose ring. This sulfide was then coupled with alkyl halides to form sulfonium ion compounds in good yields. All of the DPA and UDP-Galf analogues were tested for their ability to inhibit GlfT2, a key galactofuranosyltransferase involved in the synthesis of the galactan portion of the mycobacterial arabinogalactan. Most of the compounds showed weak inhibition of the enzyme; however, a few were moderately active and are the mode of inhibition of these analogues is currently being studied.

Le toluène (TOL), le n-hexane (HEX), le cyclohexane (CHX) et l'isooctane (ISO) sont des composés organiques volatils (COVs) omniprésents dans les milieux industriels et résidentiels. L'exposition aux mélanges soulève de nombreuses interrogations en regard des possibilités d'interaction. L'inhibition métabolique étant le mécanisme d'interaction le plus plausible, pourrait aboutir à une augmentation de leur concentration interne et donc de leur toxicité. L'objectif de cette étude était de caractériser les interactions métaboliques entre le TOL, l'HEX, le CHX et l'ISO, en utilisant les préparations microsomiales de foie de rat. Nous avons donc étudié le potentiel d'inhibition du métabolisme du TOL par HEX, CHX et ISO, aussi bien que l'inhibition du métabolisme du HEX par TOL, CHX et ISO. Initialement, la mesure du coefficient de partage milieu : air (pm : air) a aussi été faite pour permettre une estimation des concentrations des inhibiteurs et des substrats dans le milieu d'incubation (CHX : 0,23 ISO : 0,21 TOL : 2,35 et HEX : 0,04). Aussi en mesurant le taux de disparition des substrats par chromatographie en phase gazeuse après des incubations de 45 min. pour TOL et de 4 min. pour HEX, le taux de métabolisme a été déterminé pour ces 2 composés incubés individuellement ou en présences des autres COVs. Les résultats suggèrent que le métabolisme du TOL est inhibé de façon compétitive par HEX et de façon incompétitive par CHX et ISO (Ki égale respectivement 0,49, 1,84 et 1,798 μM). L'inhibition de HEX par TOI est de type mixte (Ki = 4,5339 μM), alors que le CHX et l'ISO agissent sur le métabolisme de l'HEX par inhibition compétitive (Ki respectif de 0,75 et 1,54 μM). Ces données in vitro sur les interactions métaboliques pourront être intégrées dans un modèle pharmacocinétique à base physiologique (PBPK) pour prédire la dose interne résultant d'une exposition à ces mélanges chimiques. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : toluène, hexane, cyclohexane, isooctane, métabolisme in vitro

No description available.

Universiẗat, Diss.--Paderborn, 1999.

n-Hexane and its metabolites are neurotoxic to animals and man. Studies have revealed a progressive neuropathy which affects the distal regions of motor and sensory peripheral nerves. This paper describes efforts to determine whether 2-hexanone or 2,5-hexanedione is more neurotoxic to rats when given in drinking water. Our results show that 2,5-hexanedione is more neurotoxic than 2-hexanone and that it first affects the distal axon. Concentrations of 20 mM produced no effects after 3 weeks but 40 mM increased distal latency after 2 weeks.

A vapor phase impregnation technique with Pt(acac)₂ has been developed and used to load Pt into aluminosilicate (KL, BaKL, KBaKL, NaY, CsNaY, FAU, EMT, ZSM-12 and SSZ-24) and aluminophosphate (AIP0₄-5 and VPI-5) molecular sieves. ¹³C MAS NMR, TEM and H₂ chemisorption measurements reveal that Pt can be loaded into the micropores of molecular sieves with both charged and neutral frameworks. Pt containing molecular sieves were tested as catalysts for the aromatization of n-hexane at 460 - 510°C and atmospheric total pressure in order to study the influence of Pt cluster size and support acidity/basicity, microstructure and chemical composition on activity and selectivity. High selectivity to benzene over most of the zeolite samples demonstrates that support acidity/basicity and microstructure do not contribute directly to the aromatization selectivity over Pt catalysts. A clear trend of increasing benzene selectivity with decreasing Pt cluster size is found. These observations suggest that the exceptional reactivity of Pt/KL for the aromatization of n-hexane results from the lack of any acidity in the support and the ability of zeolite L to stabilize the formation of extremely small Pt clusters. Pt/AIP0₄-5 and Pt/VPI-5 show high selectivity to n-hexane with little formation of benzene while opposite is observed for Pt/SSZ-24. The differences in catalytic behavior are attributed to variations in the environment of Pt clusters which are situated in either an aluminophosphate or silicate micropore. See document for rest of abstract. / Ph. D.

Deux zéolithes nanocristaux de type *BEA et CP814E commerciales avec de différentes propriétés texturales, et une zéolithe microcristaux de type *BEA qui a été synthétisée durant cette thèse, ont été modifiées par une desilication en utilisant de différents traitements alcalins. Toutes les zéolithes parentes et certaines désilicées ont été sélectionnée pour le craquage du n-hexane, où aucune amélioration significative de la conversion n'a été observée après la désilication. Toutes les zéolithes parentes et quelques désilicées sélectionnées ont été transformés en leur forme bifonctionnelle par imprégnation du platine pour d'étudier l'impact de la désilication dans l'hydroisomérization de n-C10. On a constaté que l'amélioration des propriétés texturales par la désilication n'était pas toujours la cause d'une augmentation ou d'une diminution de l'activité et de la sélectivité du catalyseur, mais plutôt de la localisation des particules de Pt et leur distance prédite des sites acides. Cependant, la présence des mésopores inter- et intracristallins, en plus de la distance de Pt-H+, sont des importants caractéristiques qui affectent l'activité et la sélectivité. Nous avons également étudié l'impact de la longueur de chaîne dans l'hydroisomérization de n-C12 et de n-C14. Un phénomène spécial dans le cas de n-C12 est apparu, où le rendement d'isomérisation semblait inférieur à celui obtenu sur n-C10 et n-C14, ce qui suggère que cela résulte de l'effet de confinement. La série microcristaux a montré une amélioration de l'activité dans la transformation n-C14, mais une diminution de la sélectivité des isomères à cause des limites de diffusion potentielles. / Two commercial nanocrystal *BEA zeolites with different textural properties and a microcrystal synthesized *BEA zeolite, were desilicated using different alkaline treatment; classical in presence of Noah alone, or incorporated with a pore directing agent. All parent zeolites and some selected desilicated samples were chosen for catalytic cracking of n-hexane, where no significant improvement of n-hexane conversion was observed after desilication. To investigate the impact of desilication on the hyrdoisomerization of n-C10, all parent and the some selected desilicated zeolites were transformed into their bifunctional form by platinum loading. The improvement of the textural properties by desilication using the different pore directing agents, was not always the cause behind an increase or decrease in the activity and selectivity of the catalyst, but rather was more the location of the Pt particles and their predicted distance from the acidic sites. However, the synergetic effect of both the textural and bifunctional characteristics was positive. Tests on hydroisomerization of n-C12 and n-C14 to investigate the impact of chain length were done. In the nanocrystal series, a special phenomenon on n-C12 appeared where the isomerization yield seemed to be less than that obtained on n-C10 and n-C14, suggesting that this would be due the confinement effect, which was shown to be more effective in case of n-C12. The microcrystal series showed an improvement of the activity over all the catalysts in case of n-C14 transformation, but a decrease in isomers selectivity as observed due to probable diffusional limitations within the channels of these series catalysts.

O presente trabalho teve como objetivos principais utilizar reações enzimáticas para a degradação de resíduos de laboratório e na síntese de álcoois quirais. Na primeira parte foi realizada uma triagem de microrganismos e enzimas hidrolíticas, objetivando a biorreciclagem de hexano presente no resíduo contendo uma mistura hexano-acetato de etila. Esta mistura é largamente utilizada para purificação de compostos químicos por cromatografia líquida. O método de biorreciclagem consistiu na hidrólise enzimática do acetato de etila, viabilizando, dessa forma, a recuperação do hexano puro de forma simples e rápida, pois os produtos dessa reação são altamente solúveis na fase aquosa. Na segunda parte do trabalho, avaliamos o potencial catalítico de diversas plantas comestíveis em reações orgânicas de óxido-redução visando à síntese enantiosseletiva de álcoois quirais. As reações escolhidas, para tal propósito, foram a redução de cetonas pró-quirais e a resolução cinética de álcoois via oxidação enantiosseletiva. Em muitos casos, os enantiômeros foram obtidos, separadamente, com pureza enantiomérica de até 99% dependendo da planta utilizada como biocatalizador. / The present work had as main goals the use of enzymatic reactions to degrade laboratory residues and to synthesize chiral alcohols. In the first part, it was carried out a screening of microorganisms and hydrolytic enzymes aiming the biorecycling of hexane from laboratory residues (a mixture of hexane-ethyl acetate). This misture is widely employed to purify chemicals by liquid chromatography. The biorecycling consists of enzymatic hydrolysis of ethyl acetate in a biphasic system. Due to the high solubility of the undesired products from this reaction in the aqueous phase, the hexane was easily recovered. To evaluate the possibility of treatment of effluents in a high amount, we carried out the biorecycling in a continuous system with tubular reactor using immobilized lipase (Novozyme 435). By the use of this system, the hydrolysis ratio was around 70% with no lost of enzyme stability along 6 hours work. In the second part of the work, we evaluated the catalytic potential of several edible plants in oxido-reduction reactions aiming the enantioselective synthesis of chiral alcohols. The chosen reactions were the reduction of prochiral ketones and the kinetic resolution by enantioselective oxidation. In several cases, depending of the plant employed as biocatalyst, the (R) or (S)- enantiomer were obtained in high enantiomeric purity (up to 99%). For example, the Arracacia xanthorrhiza B. (mandioquinha) performed an efficient enantioseletive reduction of 1-(4-bromophenyl)ethanone to the (S)-1-(4-bromophenyl)ethanol with 98% e.e. (enantiomeric excess), while the a Manihot esculenta (mandioca) gave the (R)-1-(4-bromophenyl)ethanol with 90% e.e. Some plants showed a good oxidative performance. For example, Coriandrum sativum L. (coentro) gave the quantitative oxidation of 1-(4-methyphenyl)ethanol to the 1-(4-metilphenyl)ethanona.