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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Studies in preparative chromatography /

Zhang, Ling. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2004. / Printout. Includes bibliographical references. Also available on the World Wide Web.
2

Design and Development of Soft Landing Ion Mobility: A Novel Instrument for Preparative Material Development

Davila, Stephen Juan 08 1900 (has links)
The design and fabrication of a novel soft landing instrument Soft Landing Ion Mobility (SLIM) is described here. Topics covered include history of soft landing, gas phase mobility theory, the design and fabrication of SLIM, as well as applications pertaining to soft landing. Principle applications devised for this instrument involved the gas phase separation and selection of an ionized component from a multicomponent gas phase mixture as combing technique to optimize coatings, catalyst, and a variety of alternative application in the sciences.
3

Isolamento em escala preparativa de ácidos anacárdicos provenientes do líquido da casca da castanha do caju (LCC)

Oiram Filho, Francisco 29 August 2017 (has links)
OIRAM FILHO, F. Isolamento em escala preparativa de ácidos anacárdicos provenientes do líquido da casca da castanha do caju (LCC). 2017. 64 f. Dissertação (Mestrado em Engenharia Química)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by pgeq ufc (pgeq@ufc.br) on 2017-10-26T17:27:44Z No. of bitstreams: 1 2017_dis_foiramfilho.pdf: 2261095 bytes, checksum: 44ef008226fa11ae68fc6ea4d6a09d08 (MD5) / Rejected by Marlene Sousa (mmarlene@ufc.br), reason: Prezado Oiram, Existe uma orientação para que normalizemos as dissertações e teses da UFC, em suas paginas pré-textuais e lista de referencias, pelas regras da ABNT. Por esse motivo, sugerimos consultar o modelo de template, para ajudá-lo nesta tarefa, disponível em: http://www.biblioteca.ufc.br/educacao-de-usuarios/templates/ Vamos agora as correções sempre de acordo com o template: 1. Na folha de dedicatória nenhuma informação deve ficar em negrito e as dedicatórias devem iniciar no centro da folha na parte inferior, com alinhamento a esquerda. Veja modelo no template. 2. Na folha de agradecimentos coloque parágrafos ao iniciar as frases. 3. A citação também deve iniciar no centro da folha na parte inferior, com alinhamento a esquerda. Veja modelo no template. 4. A ABNT não orienta a fazer lista de Apêndices. Estes devem ser inseridos no sumário. 5. No sumário não dê recuo na margem, para não caracterizar divisão em capítulos. No sumário, observe o alinhamento da margem dos títulos, de modo que ao aumentar o número de dígitos estes fiquem no mesmo alinhamento de quando tinham apenas um dígito. Quando o título não couber na mesma linha, sua continuação deve ficar na mesma margem da primeira letra da linha de cima e não voltar para a margem do numeral. Ex. 1 INTRODUÇÃO 3.13.1 Extração da lignina 3.13.2.1 Microscopia Eletrônica de Varredura 4.6 Avaliação de estratégias.... sacarificação e fermentação simultâneas 5 CONCLUSÃO REFERÊNCIAS APÊNDICE A - PERFIL CROMATOGRÁFICO.... ATENÇÃO! Colocar a palavra CONCLUSÃO no singular. Use a palavra REFERÊNCIAS e não referencias bibliográficas. Corrigir e reenviar arquivo para o secretário de seu curso. Att. Marlene Rocha 3366-9620 mmarlene@ufc.br on 2017-11-03T12:01:27Z (GMT) / Submitted by pgeq ufc (pgeq@ufc.br) on 2017-11-06T17:46:57Z No. of bitstreams: 1 2017_dis_foiramfilho.pdf: 2261032 bytes, checksum: 269a0f76af7bd7648c411c4a819df137 (MD5) / Approved for entry into archive by Marlene Sousa (mmarlene@ufc.br) on 2017-11-07T13:23:50Z (GMT) No. of bitstreams: 1 2017_dis_foiramfilho.pdf: 2261032 bytes, checksum: 269a0f76af7bd7648c411c4a819df137 (MD5) / Made available in DSpace on 2017-11-07T13:23:50Z (GMT). No. of bitstreams: 1 2017_dis_foiramfilho.pdf: 2261032 bytes, checksum: 269a0f76af7bd7648c411c4a819df137 (MD5) Previous issue date: 2017-08-29 / The shells of cashew nut are raw material for obtaining cashew nut shell liquid (CNSL) , a brownish viscous substance with important applications in the chemical and pharmaceutical industry . Several compounds are found in CNSL, such as cardol, cardanol, methyl - cardol and anacardic acids (AnAc). The A nAc are compounds considered as phenolic lipids, due they have a long carbonic chain with different degrees of instauration. Studies in several sc ientific areas show positive results of A nAc for the treatment and prevention of some diseases and their vectors. Therefore, there is a need for more specific studies to monitor, quantify and isolate these compounds in the CNSL. In this work a chromatograp hic separation method was developed, able to isolate the A nAc present in the CNSL . A fractionation of the CNSL was also performed to obtain a fraction containing only A n A c . Samples of CN SL were solubilized in methanol, injected into a high performance liquid chromatograph coupled a diode array detector (HPLC – DAD), monitored at 280 nm, equipped with C 18 column , using as the mobile phase acetonitrile, H 2 O, acetic acid in isocratic mode . The chromatographic method developed showed adequate selectivity to be able to separate anacardic acids triene (15:3 ) , diene ( 15:2 ) and monoene ( 15:1) efficiently presents in the CNSL at the retention times 7.68, 11.09 and 17.85 min, respectively. For the preparative scale chromatographic conditions was used a HPLC – DAD mon itored at wavelength 280 nm, equipped with a C 18 column , using as the mobile phase methanol, H 2 O, acetic acid in isocratic mode . The method was mathematically adjusted to obtaining a greater similarity with the analytical method. The calibration curve w ith linear interval (50 to 1000 μg.mL - 1 ) and validation of the analytical method were made from the external anacardic acid standard (15: 3). The results obtained for method validation were satisfactory for intra - day (CV = 0.60 %) and inter - day (CV = 0.67 %) precision, linearity (y = 2670.8x - 26949, r 2 > 0.9998), repeatability for the retention time (CV = 1.02 %) and area (CV = 0.24 %), selectivity and limits of detection (19,8 μg.mL - 1 ) and quantification (60.2 μg.mL - 1 ). The recovery results obtained by th e purification of the anacardic acid on a preparative scale were 94.02, 87.63 and 97.35 %, for the triene, dieno and monoene, respectively . The data for purity were 99.11, 95.56 and 92.59 % , for the triene, diene and monoene, respectively. The s olvent consumption was 60.52 and 11.09 mL.mg - 1 for analytical and preparative scale, respectively. The productivity was 0.06 and 1.63 g.h - 1 by each g of adsorbent to analytical and preparative scale, respectively. The chromatographic method developed and i ts respecti ve scale - up were adequate for the quantification, monitoring and isolation of the an acardic acids present in the CNSL. The method was validated according to the required standards and the isolation of the analytical standard s was obtained with a n high degree of purity, recovery, low solvent consumption and good productivity. / A casca da castanha de caju é matéria-prima para obtenção do líquido da casca da castanha (LCC), uma substância viscosa de coloração amarronzada, com importantes aplicações na indústria química e farmacêutica. Diversos compostos são encontrados no LCC, tais como, cardol, cardanol, metil-cardol e os ácidos anacárdicos (AcAn). Os AcAn são compostos considerados lipídeos fenólicos, pois possuem uma cadeia carbônica longa com diferentes graus de instauração. Estudos em diversas áreas da ciência mostram resultados positivos dos AcAn para tratamento e prevenção de algumas doenças e seus vetores. Portanto, há uma necessidade de estudos mais específicos para monitorar, quantificar e isolar esses compostos no LCC. Nesse trabalho foi desenvolvido um método de separação cromatográfica, capaz de isolar os AcAn presentes no LCC. Também foi executado um fracionamento do LCC para obter uma fração contendo apenas AcAn. Amostras de LCC natural foram solubilizadas em metanol, injetadas em um cromatógrafo líquido de alta eficiência acoplado a um detector de arranjo de diodo (CLAE-DAD) monitorado a um comprimento de onda de 280 nm, equipado com uma coluna C18, utilizando como fase móvel acetonitríla, H2O e ácido acético, em modo isocrático. O método cromatográfico desenvolvido apresentou seletividade adequada, sendo capaz de separar os ácidos anacárdicos trieno (15:3), dieno (15:2) e monoeno (15:1) de maneira eficaz, presentes no LCC nos tempos de retenção de 7,68, 11,09 e 17,85 min, respectivamente. Para as condições cromatográficas em escala preparativa, foi usado um CLAE-UV/VIS monitorado à um comprimento de onda de 280 nm, equipado com uma coluna C18 em escala preparativa, utilizando como fase móvel metanol, H2O e ácido acético, em modo isocrático. O método em escala preparativa foi ajustado matematicamente para obter maior similaridade com o método analítico. A curva de calibração com intervalo linear (50 a 1000 µg.mL-1) e validação do método analítico, foram feitos a partir do padrão externo do ácido anacárdico (15:3). Os resultados obtidos para validação do método foram satisfatórios, para precisão intra-dia (CV = 0,60 %) e inter-dia (CV = 0,67 %), linearidade (y = 2670,8x - 26949, r2 > 0,9998), repetibilidade para o tempo de retenção (CV = 1,02 %) e área (CV = 0,24 %), seletividade e limites de detecção (19,8 µg.mL-1) e quantificação (60,2 µg.mL-1). Os resultados da recuperação do isolamento em escala preparativa dos AcAn foram 94,02, 87,63 e 97,35 %, para os AcAn trieno, dieno e monoeno, respectivamente. Os valores de pureza foram 99,11, 95,56 e 92,59 %, para treino, dieno e monoeno, respectivamente. O consumo de solvente foi de 60,52 e 11,09 mL.mg-1, para escala analítica e preparativa, respectivamente. A produtividade foi de 0,06 e 1,63 g.h-1 por cada g de adsorvente para escala analítica e preparativa, respectivamente. O método cromatográfico desenvolvido e sua respectiva ampliação de escala foram adequados para a quantificação, monitoramento e isolamento dos ácidos anacárdicos presentes no LCC. O método foi validado de acordo com as normas exigidas e o isolamento dos padrões analíticos foi obtido com elevado grau de pureza, recuperação, baixo consumo de solvente e boa produtividade.
4

Réflexions sur la notion de contrat préparatoire / The notion of preparative contract

Sarvary-Bene, Peter 14 December 2015 (has links)
La notion de contrat préparatoire est étudiée en tant que telle dans cette étude, plus que les contrats préparatoires individuellement. L’objectif était de découvrir la légitimité de la notion de contrat préparatoire. La notion de contrat préparatoire est une notion née de la doctrine, enrichie par la pratique, délaissée par la jurisprudence et inexistante dans le cadre de la loi. Ceci étant, la notion existe. Son identification n’est pas aisée. Elle est parfois assimilée à d’autres notions existantes telles que celle d’avant-contrat, parfois opposée à ces mêmes notions. Les contours de la notion de contrat préparatoire sont flous pour la doctrine, très partagée. Définir des critères d’identification négatifs et positifs est une tâche complexe tant les contrats préparatoires diffèrent selon la conception que l’on en a. Des critères ont été dégagés. La notion de contrat préparatoire recouvre l’ensemble des contrats ayant pour objet la préparation de la conclusion du contrat définitif. Prise ainsi, la définition semble large et permet d’inclure un grand nombre de contrats. L’étude de la pertinence de la notion de contrat préparatoire aboutit toutefois à une réduction drastique de ce qu’est la notion. L’absence de régime commun propre à la catégorie que pourrait être la notion de contrat préparatoire nous conduit à réduire sa pertinence à un usage pratique et pédagogique, la notion n’étant point pertinente en tant que telle. Tel est le cas tout au moins jusqu’à la prochaine réforme du droit des contrats qui pourrait créer un régime commun de sanction des contrats préparatoires propre à dégager des critères effectifs de la notion. / The concept of preparatory contract is considered as itself in this work, more than preparatory contracts separately. The objective was to discover the legitimacy of the concept of preparatory contract. The concept of preparatory contract is a concept born to the doctrine, enriched by practice, neglected by the courts and non-existent under the law. Whereas, the concept exists. His identification is not easy. It is sometimes equated with other existing concepts such as pre-contract, sometimes opposed to those concepts. The determination of the concept of preparatory contract is unclear for very divided doctrine. Define negative and positive identification criteria is a complex task when the preparatory contracts differ so much depending on the conception that we have. Criteria have been cleared, the notion of preparatory contract covers all contracts relating to the preparation of the conclusion of the final contract. Taken like that, the definition seems wide and is used to include a large number of contracts. Only the study of the relevance of the concept of preparatory contract eventually leads to a drastic reduction of what the concept is. The lack of clean common system to the category could be the notion of preparatory contract leads us reduce its relevance to practical and educational purposes, the notion being legally relevant points ; until the next implementation of the reform of contract law which could create a common system of punishment of preparatory own contracts to generate effective criteria of the concept .
5

The effect of organic peroxides on the molecular composition of heterophasic ethylene-propylene impact copolymers

Magagula, Sifiso Innocent 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Heterophasic ethylene-propylene copolymers, also known as impact polypropylene (PP) copolymers (IPCs) or heterophasic copolymers (HECOs), are a unique group of polyolefins produced through the copolymerisation of ethylene and propylene, with the aim of improving the impact properties of the PP homopolymer at low temperatures. Therefore, this polymer comprises of a PP homopolymer matrix with a dispersed rubbery copolymer phase. Due to their unique properties, HECO polymers have become commercially important materials, with a wide range of applications. Therefore a fundamental understanding of the processes and chemistry that affects their final macroscopic properties needs to be expanded. The main focus of this investigation was to understand why specific organic peroxides influence or interact differently with the various phases of HECO polymers, in order to utilize their properties to obtain HECO polymers with optimal and desired properties. Two HECO polymers with different ethylene contents were fractionated into three fractions (30, 100 and 130 °C), using preparative temperature rising elution fractionation (P-TREF). Each individual TREF fraction was degraded with two different types of organic peroxides, and then characterised using four different analytical tools. The changes in the molecular structures of the different fractions were investigated by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The changes in comonomer sequence distributions were investigated by carbon 13 nuclear magnetic resonance spectroscopy (13C-NMR). Moreover, the degradation of the different fractions was investigated by high temperature size exclusion chromatography (HT-SEC). The investigation showed that the HECO polymers with different ethylene contents were uniquely altered. It was evident that the ethylene content influenced the degradation behaviour of the HECO polymers. The ability of the peroxide to affect certain regions of the HECO polymer more than others is highly dependent upon its miscibility with certain regions of the HECO polymers. The “visbreaking” efficiency of a specific organic peroxide appears to be primarily dependent on the number of “peroxy” groups it contains in its molecular structure. Stellenbosch University https://scholar.sun.ac.za / AFRIKAANSE OPSOMMING: Heterofase etileen-propileen ko-polimere, ook bekend as impak PP ko-polimere (IPCS) of heterofase ko-polimere (HECO), is 'n unieke groep poliolefiene geproduseer deur die ko-polimerisasie van etileen en propileen, met die doel op die verbetering in die impak eienskappe van die PP homopolimeer by lae temperature. Hierdie polimeer bestaan dus uit 'n PP homopolimeer matriks met 'n verspreide rubberagtige ko-polimeer fase. As gevolg van hul unieke eienskappe, is HECO polimere van kommersiële belang, met 'n wye verskeidenheid van toepassings. 'n Fundamentele begrip van die prosesse en chemie wat die finale makroskopiese eienskappe beïnvloed moet dus uitgebrei word. Die hooffokus van hierdie ondersoek was om te verstaan waarom spesifieke organiese peroksiede verskillende invloede en interaksies met die verskillende fases van HECO polimere het, om sodoende van hul eienskappe gebruik te maak om HECO polimere te verkry met optimale en gewenste eienskappe. Twee HECO polimere met verskillende etileen inhoud was gefraksioneer in drie fraksies (30, 100 en 130 °C), met behulp van preparatiewe temperatuur styging eluering fraksionering (P-TREF). Elke individuele TREF fraksie was gedegradeer met twee verskillende tipes organiese peroksiede en daarna gekarakteriseer deur vier verskillende analitiese metodes. Die veranderinge in molekulêre strukture van die verskillende fraksies was geondersoek met behulp van Fourier transform infrarooi spektroskopie (FTIR) en differensiële skandering kalorimetrie (DSC). Die veranderinge in ko-monomeer volgorde distribusie was bestudeer deur middel van kern magnetiese resonans spektroskopie (KMR). Verder was die degradasie van die verskillende fraksies met behulp van hoë temperatuur grootte uitsluitingschromatografie (HT-SEC) bestudeer. Die ondersoek het getoon dat die HECO polimere met verskillende etileen inhoud uniek gedegradeer was. Dus is dit duidelik genoeg dat die etileen inhoud die degradasie gedrag van die HECO polimere beïnvloed het. Die vermoë van die peroksied om sekere areas van die HECO polimeer meer as ander te beïnvloed is hoogs afhanklik van die mengbaarheid met sekere areas van die HECO polimere. Die "visbreking" doeltreffendheid van 'n spesifieke organiese peroksiede is meestal afhanklik van die aantal "peroksie" groepe in die molekulêre struktuur.
6

Adsorption Studies with Liquid Chromatography : Experimental Preparations for Thorough Determination of Adsorption Data

Edström, Lena January 2014 (has links)
Analytical chemistry is a field with a vast variety of applications. A robust companion in the field is liquid chromatography, the method used in this thesis, which is an established workhorse and a versatile tool in many different disciplines. It can be used for identification and quantification of interesting compounds generally present in low concentrations, called analytical scale chromatography. It can also be used for isolation and purification of high value compounds, called preparative chromatography. The latter is usually conducted in large scale with high concentrations. With high concentrations it is also possible to determine something called adsorption isotherms. Determination of adsorption isotherms is a useful tool for quite a wide variety of reasons. It can be used for characterisation of chromatographic separation systems, and then gives information on the retention mechanism as well as provides the possibility to study column-column and batch-batch reproducibility. If a protein is immobilised on a solid support, adsorption isotherms can be used for pharmacological characterisation of drug-protein interactions. Moreover, they can be used for the study of unexpected chromatographic phenomena. If the adsorption isotherm is known it is also possible to simulate chromatograms, and subsequently optimise the separation process numerically. The gain of a numerically optimised separation process is higher purity or yield of valuable compounds such as pharmaceuticals or antioxidants, as well as reducing the solvent usage. Taken all together, it saves time, money and the environment. However, the process of the adsorption isotherm determination requires a number of careful experimental considerations and preparations, and these are the main focus of the thesis. Important steps along the way include the choice of separation system and of suitable analytes, preparation of mobile phases and sample solutions, calibration, determination of injection profiles and column void, and of course the adsorption isotherm determination method itself. It is also important to keep track of parameters such as temperature and pH. These issues are discussed in this thesis. At the end, a description of useful methods for processing of the raw adsorption isotherm data is presented, as well as a brief passage on methods for numerical optimisation.
7

Purifikace florizinu z listů Malus domestica Borkh. extrakcí na pevné fázi a semipreparativní vysokoúčinnou kapalinovou chromatografií. / Purification of phlorizin from Malus domestica Borkh. leaves by solid-phase extraction and semi-preparative high performance liquid chromatography.

Prachařová, Eva January 2018 (has links)
DIPLOMA THESIS Purification of phlorizin from Malus domestica Borkh.by solid-phase extraction and semi-preparative high-performance liquid chromatography Eva Prachařová Charles University, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Botany The aim of this diploma thesis was to find the best conditions for purification of a flavonoid extract from leaves of Malus domestica Borkh., and obtaining the purest fraction of phlorizin. Phlorizin may be used in the treatment of diabetes mellitus type 2 in the future, it has the ability to reduce glycemia by reducing the absorption of glucose in the small intestine and by increasing urinary glucose excretion. The first step was to find an SPE cartridge with a suitable sorbent and a suitable eluent for solid phase extraction. The DPA-6S cartridge and 100% methanol as an eluentwerefound to be the most suitable for SPE. The next step was to find the best possible conditions for semi-preparative HPLC using an ACE 5 C18 column (5 μm, C18, 150 x 10 mm i.d., 150 mm length). The mobile phase consisted of 1% (v/v) acetic acid in water (solvent A) and ethanol 100% (v/v) (solvent B), and a linear gradient elution was used (10-100% B), 0-60 min, the flow: 1mL/min. This method resulted in the 91.05% purity of phlorizin. Keywords: phlorizin, SPE,...
8

Soft Landing Ion Mobility Mass Spectrometry: History, Instrumentation and an Ambient Pressure Application

Birdwell, David 12 1900 (has links)
Preparative mass spectrometry is an important method for the synthesis of new materials. Recently, soft landing mass spectrometry has been used to land ions on surfaces to coat or otherwise alter them. Commercial soft landing instruments do not yet exist, and the physical phenomenon of soft landing has not yet been fully described. For future ion mobility soft landing research, the theory of ion mobility, ion optics and soft landing is discussed, and 2 soft landing instruments have been built and described, along with proof of concept experiments for both instruments. Simulations of the process of ion mobility and ion optics for use in these instruments, as well as some preliminary results for the optics are included. Surfaces described include copper on mica and iron on silicon. Self assembly of soft landed ions is observed on the surfaces. The instruments constructed will be useful for future soft landing research, and soft landing can be used for future materials research with special attention focused on the self-assembly of the landed ions.
9

Elektrochemická oxidace žlučových kyselin na elektrodách na bázi uhlíku. Možnosti využití v elektroanalýze. / Electrochemical oxidation of Bile Acids on Carbon Based Electrodes. The Possible Use in Electroanalysis.

Klouda, Jan January 2015 (has links)
The goal of this master's thesis was to examine the possibility of oxidation of seven selected bile acids and evaluate whether such processes are suitable for analytical purposes. The secondary goal was to describe the oxidation products of bile acid electrolysis. The experiments were carried out in a non-aqueous medium of acetonitrile and in a mixed medium of acetonitrile:water using linear sweep and cyclic voltammetry. The working electrode materials employed for voltammetric experiments were: highly oriented pyrolytic graphite, -cyclodextrin modified glassy carbon and boron doped diamond. Preparative electrolysis was carried out on a platinum electrode in the non-aqueous medium of acetonitrile. Experiments have shown that neither the highly oriented pyrolytic graphite electrode nor the -cyclodextrin modified glassy carbon electrode are suitable for analytical purposes under conditions used. The results achieved on the boron doped diamond electrode, on the other hand, have not yet been described in the literature. Primary bile acids cholic and chenodeoxycholic were oxidized at approximately 0.5 V lower potential in the mixed medium of acetonitrile:water than in the papers using carbon electrodes published until now. Products of oxidation on the platinum electrode were separated by TLC and...
10

QSPR a elektrochemická oxidace derivátů N-benzylsalicylthioamidů / QSPR and Electrochemical Oxidation of N-benzylsalicylthioamides

Kohoutová, Petra January 2013 (has links)
The study of the substituent effect on the voltammetric behaviour of newly synthesized N benzyl-salicylthioamides and the preparation and identification of products of their electrooxidation were the aims of this thesis. The voltametric characteristics were measured by DC voltammetry on a rotating disc electrode in a non-aqueous media. Using QSER, the effect of substituents on the anodic half wave potential was quantified, and statistically valid correlation equations were obtained. The influence of reaction media on the compounds electrooxidation was also studied. Using preparative electrolysis, the electrooxidation products of two selected N benzylsalicylthioamides were obtained. The one (structurally similar) product was identified in both cases. The following general scheme of electrochemical oxidation of N-benzylsalicylthioamides studied was proposed: the electrooxidation starts on sulphur atom by elimination of electrons, followed by translocation of charge on nitrogen atom, then hydrogen sulphite is eliminated, and a new ring is closed between two molecules of appropriate N-benzylsalicylthioamide.

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