• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 37
  • 25
  • 21
  • 5
  • 3
  • 3
  • 3
  • 1
  • 1
  • Tagged with
  • 113
  • 113
  • 33
  • 32
  • 23
  • 23
  • 17
  • 15
  • 11
  • 9
  • 8
  • 8
  • 8
  • 7
  • 7
  • 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.
101

Planejamento experimental aplicada a um novo separador l?quido-l?quido utilizado no tratamento de ?guas residuais contaminadas com petr?leo

Fernandes J?nior, Wilaci Eutr?pio 05 April 2002 (has links)
Made available in DSpace on 2014-12-17T15:01:20Z (GMT). No. of bitstreams: 1 WilaciEFJ.pdf: 1838358 bytes, checksum: 40ec11f34b65cc0544a9b15c91dae65a (MD5) Previous issue date: 2002-04-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work had as objective to apply an experimental planning aiming at to improve the efficiency of separation of a new type of mixer-settler applied to treat waste water contaminated with oil. An unity in scale of laboratory, was installed in the Post-graduation Program of Chemical Engineering of UFRN. It was constructed in partnership with Petrobras S.A. This called device Misturador-Decantador a Invers?o de Fases (MDIF) , possess features of conventional mixer-settler and spray column type. The equipment is composed of three main parts: mixing chamber; chamber of decantation and chamber of separation. The efficiency of separation is evaluated analyzing the oil concentrations in water in the feed and the output of the device. For the analysis one used the gravimetric method of oil and greases analysis (TOG). The system in study is a water of formation emulsified with oil. The used extractant is a mixture of Turpentine spirit hydro-carbons, supplied for Petrobras. It was applied, for otimization of the efficiency of separation of the equipment, an experimental planning of the composite central type, having as factorial portion fractionary factorial planning 2 5-2, with the magnifying of the type star and five replications in the central point. In this work, the following independents variables were studied: contents of oil in the feed of the device; volumetric ratio (O/A); total flowrate ; agitation in the mixing chamber and height of the organic bed. Minimum and maximum limits for the studied variables had been fixed according previous works. The analysis of variance for the equation of the empirical model, revealed statistically significant and useful results for predictions ends. The variance analysis also presented the distribution of the error as a normal distribution and was observed that as the dispersions do not depend on the levels of the factors, the independence assumption can be verified. The variation around the average is explained by 98.98%, or either, equal to the maximum value, being the smoothing of the model in relation to the experimental points of 0,98981. The results present a strong interaction between the variable oil contents in the feed and agitation in the mixing chamber, having great and positive influence in the separation efficiency. Another variable that presented a great positive influence was the height of the organic bed. The best results of separation efficiency had been obtained for high flowrates when associates the high oil concentrations and high agitation. The results of the present work had shown excellent agreement with the results carried out through previous works with the mixer-settler of phase inversion / O presente trabalho teve como objetivo otimizar a efici?ncia de separa??o de um novo aparelho do tipo misturador-decantador aplicado ao tratamento de ?guas residu?rias contaminadas com petr?leo. Foi utilizado um equipamento em escala de laborat?rio, instalado no Programa de P?s-gradua??o em Engenharia Qu?mica da UFRN, que foi constru?do em parceria com a Petrobras S.A. Este aparelho denominado Misturador-Decantador ? Invers?o de Fases (MDIF), possui caracter?sticas de um misturador-decantador convencional e de uma coluna tipo spray. O equipamento ? composto de tr?s partes principais: c?mara de mistura; c?mara de decanta??o e c?mara de separa??o. A efici?ncia de separa??o ? avaliada analisando-se as concentra??es de ?leo em ?gua na alimenta??o e na sa?da do aparelho. Para a an?lise utilizou-se o m?todo da an?lise de ?leo e graxas (TOG) por gravimetria. O sistema em estudo ? uma ?gua de forma??o emulsionada com ?leo. O extratante utilizado ? uma mistura de hidrocarbonetos denominada de Aguarr?s, fornecido pela Petrobras. Aplicou-se, para a otimiza??o da efici?ncia de separa??o do equipamento, um planejamento experimental do tipo central composto, tendo como por??o fatorial o planejamento fatorial fracion?rio 2 5-2, com a amplia??o do tipo estrela e cinco repeti??es no ponto central. Neste trabalho, estudam-se as seguintes vari?veis independentes: teor de ?leo na ?gua residu?ria de carga da coluna; rela??o volum?trica org?nico/aquoso (O/A); vaz?o efetiva total; agita??o na c?mara de mistura e altura do leito org?nico. Foram fixados limites m?nimos e m?ximos para as vari?veis estudadas de acordo com trabalhos realizados anteriormente. A an?lise de vari?ncia para a equa??o do modelo emp?rico, mostrou-se estatisticamente significante e ?til para fins preditivos. A an?lise de vari?ncia tamb?m apresentou a distribui??o do erro como uma distribui??o normal e observou-se que como as dispers?es n?o dependem dos n?veis dos fatores, a suposi??o de independ?ncia pode ser verificada. A varia??o em torno da m?dia ? explicada por 98,98%, ou seja, igual ao valor m?ximo explic?vel, sendo o ajuste do modelo em rela??o aos pontos experimentais de 0.98981. Os resultados apresentam uma intera??o muito forte entre as vari?veis teor de ?leo e agita??o na c?mara de mistura, tendo grande e positiva influ?ncia na efici?ncia de separa??o. Outra vari?vel que apresentou-se com grande e positiva influ?ncia foi a altura do leito org?nico. Os melhores resultados de efici?ncia de separa??o foram obtidos para altas vaz?es quando associadas a altas concentra??es de ?leo e alta agita??o. Os resultados obtidos no presente trabalho mostraram excelente concord?ncia com os resultados de trabalhos anteriores realizados com o misturador-decantador ? invers?o de fases
102

Estendendo a caracterização dos compostos nitrogenados em resíduo de vácuo por FT-ICR MS / Extending the characterization of nitrogen compounds in vacuum residue by FT-ICR MS

Vasconcelos, Géssica Adriana 10 March 2016 (has links)
Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2016-08-17T21:37:32Z No. of bitstreams: 2 Dissertação - Géssica Adriana Vasconcelos - 2016.pdf: 2159448 bytes, checksum: a3e5f1ad74eff4a8b0472438d2a2bbf0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Cláudia Bueno (claudiamoura18@gmail.com) on 2016-08-17T21:39:28Z (GMT) No. of bitstreams: 2 Dissertação - Géssica Adriana Vasconcelos - 2016.pdf: 2159448 bytes, checksum: a3e5f1ad74eff4a8b0472438d2a2bbf0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-08-17T21:39:28Z (GMT). No. of bitstreams: 2 Dissertação - Géssica Adriana Vasconcelos - 2016.pdf: 2159448 bytes, checksum: a3e5f1ad74eff4a8b0472438d2a2bbf0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-10 / Outro / Petroleomics by FT-ICR MS was able to characterize petroleum and its derivatives at molecular level. The most used ionization source on the analysis of these compounds is electrospray. However, species that are more basic or more acidic suppress the ionization of other compounds with less strength. This disadvantage consists of, especially in positive mode, only detecting compounds with higher pKa values preventing the mass spectrometer from reading less basic species that is also present in the sample. In view of this, the development of new methods whose purpose is to minimize these effects is essential. An alternative is to use fast techniques of extraction and separation followed by analysis by FT-ICR MS. This study pursued two goals: first, to perform an extraction of vacuum residue into basic and neutral nitrogen compounds using different methods, and second, to fractionate the basic nitrogen compounds present in RV according to their mass/ratio. Three methods were tested to achieve the first objective: solvent extraction (LLE), column chromatography (LC), and solid phase extraction (SPE). The results showed that LLE was the less selective technique among all three studied procedures. SPE and LC showed similar results, and they allowed to partially separate the basic nitrogen compounds from neutral species. To accomplish the second goal, a fractionation using SPE was applied to the vacuum residue sample. This procedure permitted to detect compounds that apparently were not present in the untreated sample as a consequence of a reduction on ion suppression effect. Electrospray ionization and high resolution mass spectrometry (FT-ICR MS) were employed on the analysis of each sample. / A petroleômica por FT-ICR MS foi capaz de caracterizar o petróleo e seus diferentes derivados a nível molecular. A fonte de ionização mais utilizada na análise destes compostos é o electrospray. Componentes mais básicos e mais ácidos, entretanto, suprimem a ionização de outras espécies com menor força. A grande desvantagem deste fato consiste, especialmente no modo positivo, detectar somente os compostos com elevado pKa impedindo a leitura das espécies menos básicas presentes na mesma amostra. À vista disso, é fundamental o desenvolvimento de novos métodos que tenham por finalidade minimizar estes efeitos. Uma alternativa é fazer o uso de técnicas rápidas de extração e separação seguida pelas análises por FT- ICR MS. Desta forma, este estudo teve dois objetivos principais: primeiro, realizar uma extração dos compostos nitrogenados de resíduo de vácuo em suas frações básica e neutra utilizando diferentes métodos e, segundo realizar um fracionamento dos compostos nitrogenados básicos presentes em RV de acordo com a sua massa. Para se alcançar o primeiro objetivo, três métodos foram testados: Extração líquido-líquido (LLE), cromatografia em coluna clássica (LC) e extração em fase sólida (SPE). Os resultados mostraram que o LLE foi a menos seletiva dentre os três procedimentos estudados. SPE e LC apresentaram resultados semelhantes e foi possível separar parcialmente os compostos básicos das espécies neutras. Para alcançar o segundo objetivo, um fracionamento utilizando extração em fase sólida foi empregado na amostra de resíduo de vácuo. Este procedimento permitiu detectar compostos que aparentemente não estavam presentes na amostra não tratada como consequência da redução do efeito de supressão iônica. A ionização por electrospray e por espectrometria de massa de alta resolução (FT-ICR MS) foram utilizados na análise de cada amostra.
103

Novos dispositivos de microextração e pré-concentração para eletroforese capilar utilizando membranas microporosas ou processos eletroquímicos e sua potencialidade na análise de aminas e metais / New devices to extraction and preconcentration with microporous membranes and electrochemical procedures prior to capillary electrophoresis: some applications to amines and metals analysis

Osmar Antunes Junior 13 October 2008 (has links)
A eletroforese capilar (CE) é uma técnica de separação eficiente, que tem merecido grande atenção nas últimas duas décadas, e que oferece soluções analíticas alternativas ou complementares à cromatografia líquida num número crescente campos de aplicação, incluindo análises de fármacos, compostos biológicos e biogênicos, dentre outros. Entre as vantagens comparativas da técnica figuram separações mais rápidas com pequeno dispêndio de amostras, solução tampão (e solvente orgânico, se usado), baixo custo de operação e manutenção. Todavia, a exigüidade de amostra no capilar tem como reflexo, via de regra, limites de detecção menos favoráveis que os da HPLC, uma limitação significativa na análise de traços, suplantável por técnicas e procedimentos de extração/acumulação prévia dos analitos. Nesta tese concebeu-se e implementou-se a combinação inédita entre a CE e a préconcentração eletroquímica de metais. Novos dispositivos para extração líquido/gás/líquido mediada por membranas microporosas também foram propostos e aplicados à analise de aminas voláteis, sempre utilizando detector de condutância medida sem contato direto com a solução (C4D, contactless capacitively coupled conductivity detection). Primeiramente, sem recorrer à preconcentração, definiu-se condições de análise para 16 aminas (metilamina, dimetilamina, trimetilamina, propilamina, n-butilamina, s-butilamina, t-butilamina, hexilamina, DMAE, etanolamina, dietanolamina, trietanolamina, 1,3-diaminopropano, 1,4-diaminobutano, 1,5-diaminopentano e 1,6-diaminohexano) juntamente com íon amônio, e, para análise de 9 metais (TI++, Cd2+, Pb2+,Cr3+, Zn2+, Ag+, Cu2+, Co2+ e Ni2+). Um método completo para análise de dimetilaminoetanol em formulações cosméticas por CE-C4D foi desenvolvido e validado. Os estudos de extração e pré-concentração líquido/gás/líquido foram realizados utilizando filamento oco de Oxyphan preenchido com solução coletora. Foi construída cela para extração gasosa constituída de recipiente fechado no qual se introduz amostra com analitos voláteis, ou volatilizáveis pela adição de reagente e/ou aquecimento (pervaporação). A bobina coletora de filamento oco preenchido com solução coletora foi montada na parte interna da tampa da cela. Testes realizados com amostras de tecidos de peixe demonstraram o funcionamento do sistema, que poderá ser aperfeiçoado e aplicado, por exemplo, à análise de aminas biogênicas primárias de baixo peso molecular, indicadoras de decomposição de certos alimentos. Criou-se também extrator microvolumétrico em que o filamento de Oxyphan é montado concentricamente no interior de um capilar de sílica fundida, para realização de estudos de extração líquido/gás/líquido em fluxo. Um sistema em fluxo compreendendo válvulas e microbombas foi montado e colocado sob controle de um programa de computador (Labview), que, entre outras funções, controla o deslocamento da solução coletora exposta no filamento oco (13 µL) até o ponto exato da interface em que se dá a injeção no capilar da CE. Pela primeira vez recorreu-se à acumulação eletroquímica (ECPC) de analitos num sistema FIA-CE-C4D - uma configuração baseada inteiramente na eletroquímica -, visando expandir os limites de detecção das determinações e eliminar interferência de matriz por troca de meio. Implementou-se a pré-concentração catódica seguida de redissolução anódica com uma célula eletroquímica especial, em que o capilar da eletroforese é posicionado junto ao eletrodo de trabalho, feito de ouro obtido a partir de CD\'s graváveis. Uma célula microfluídica ECPC-FIA-CE-C4D também foi construída. Tomando íons Cu2+ como sistema modelo, demonstrou-se o aumento do sinal referente aos íons cobre(lI) no eletroferograma para tempos crescentes de acumulação eletroquímica. Para a solução de alto teor salino contendo mistura dos íons Cd(II), Pb(II), Zn(lI) e Cu(II), comprovou-se a eliminação da interferência da matriz por troca de meio antes da redissolução anódica. Os testes iniciais indicam que os novos dispositivos e sistemas propostos nesta tese para uso em conjunto com a CE têm potencialidade para desencadear novas pesquisas, desenvolvimento de métodos e aplicações, sendo passíveis também de miniaturização e automação. / Capillary electrophoresis (CE) is an efficient separation technique that evolved rapidly in the last couple of decades, now offering complementary or alternative analytical solutions to liquid chromatography for an expanding number of application fields including drugs, biological and biogenic compounds. Some comparative advantages of CE are faster separation, very low consumption of buffer solutions and samples (and organic solvents, if any), lower maintenance and operational costs. However, the quantification of a few nanoliters of analyte in a capillary, as a rule, compromises the detection limits attainable by HPLC, a shortcomming in trace analysis, suplantable by extraction/preconcentration of the analytes from the sample. The combination of electrochemical preconcentration (ECPC) with CE is first proposed in this thesis and tested with metal ions. New devices for liquid/gas/liquid extraction based on microporous filaments filled with a collector solution were proposed and applied to the analysis of volatile amines, The detector of choice was the C4D (capacitively coupled contactless conductivity detection) and CE-C4D working conditions were defined for the separation and determination of: i) 16 amines (methylamine, dimethylamine, trimethylamine, propylamine, n-butylamine, s-butylamine, t-butylamine, hexilamine, ethanolamine, diethanolamine, triethanolamine, DMAE, 1,3-diaminopropane, 1,4- diaminobutane, 1,5-diaminopentane and 1,6-diaminohexane) plus ammonium, ii) nine metallic ions (Tl+, Cd2+, Pb2+, Cr3+ Zn2+, Ag+, Cu2+, Co2+ e Ni2+). A complete method of analysis for Dimethyl-amino-ethanol (DMAE) in cosmetic formulations was established and validated. Liquid/gas/liquid extraction studies were based on the use of a polypropylene microporous filment (Oxyphan® ) filled with the collection solution. A closed cell was devised in which an Oxyphan® coil is installed beneath the cap and volatilization of sample components can be promoted by heating (pervaporation) or addition of a reactant. The device was successfully tested with fish samples by the detection of primary low molecular weight biogenic amines, a procedure of special interest in fast checking of fish or other foods for decomposition. A microvolumetric version of the liquid/gas/liquid extractor was created with an Oxyphan® hollow fiber mounted concentrically inside a silica capillary. A flow system comprising the micropumps, solenoid valves and the microextrator was designed, automatically operated under software control (Labview). This FIA-CE system was tested by the extraction/enrichment of volatile amines in the collecting solution (13 µL) followed by accurate displacement to the interface with the CE capillary by the micropumps. Pioneering work with ECPC-FIA-CE-C4D an all-electrochemical system was conducted in this thesis aiming expanded detection limits and matrix effect reduction. An electrochemical cell for the interface with FIA-CE system was built in acrylic using gold electrodes made from gold-sputtered CD-Rs. A microfluidic version of the cell interfaced with the CE capillary was also conceived. The full system was evaluated by using Cu2+ as a model specie; an increase in analytical signal was observed as a function of the cathodic deposition time before stripping. For a mixture of Cd2+, Cu2+, Zn2+ and Pb2+ in a high saline media, elimination of the matrix interference by medium exchange before stripping was demonstrated. Initial favorable evaluations show that the devices and systems proposed in 12 the thesis have the potential to engender further research of methods and applications as well as miniaturization and automation of procedures.
104

Comparação entre analisadores com fluxo constante ou pulsado: aplicação a amostras de relevância farmacêutica, agronômica e/ou ambiental / Comparison of flow analyzers exploiting constant or pulsed flows: application to samples of pharmaceutical, agronomical and/or environmental relevance

Milton Katsumi Sasaki 24 November 2015 (has links)
Sistemas de análises químicas em fluxo com multi-impulsão empregam bombas solenoide como unidade propulsora de fluidos, as quais proporcionam fluxos pulsados. Estes provêm um eficiente transporte radial de massas, o que garante boa homogeneização das soluções envolvidas, mesmo em situações de dispersão limitada. O objetivo principal deste trabalho foi então comparar o desempenho de metodologias envolvendo reagentes imobilizados em sistemas de análises em fluxo com fluxos constantes ou pulsados. Para isto, foram selecionadas as determinações espectrofotométricas de ácido ascórbico em produtos farmacêuticos, utilizando reator tubular de polietileno (50 cm) com MnO2(s) imobilizado, e reação com formaldoxima (0,25 mol L-1); e de carbaril em águas naturais, explorando extração líquido-líquido com xileno imobilizado em membrana de PVDF, e solução de NaOH a 0,1 mol L-1 como fluxo aceptor. Adicionalmente, compararam-se os dois tipos de fluxo em uma nova titulação em fluxo, a titulação monitorada por traçador; a determinação de acidez total em vinagres foi selecionada e utilizaram-se as titulações por injeção em fluxo e programada em triângulo, ambas empregando solução de NaOH a 0,01 mol L-1 como titulante e fenolftaleína como indicador ácido-base, com monitoramento por traçador empregando azul brilhante FCF (ca. 6 mg L-1). Na determinação de ácido ascórbico, o desempenho do sistema com fluxos pulsados foi superior àquele com fluxos constantes quanto ao limite de detecção: 0,33 contra 0,60 mg L-1 (critério 3,3 ?), e à repetibilidade: d.p.r. estimado como 2,5 contra 5,6% (n = 20); quanto à exatidão, não foi encontrada diferença estatisticamente significativa entre o método proposto e o da Farmacopeia Britânica ao nível de confiança de 95%. Na determinação de carbaril, o uso de fluxos pulsados favoreceu a extração do analito, obtendo-se uma sensibilidade 9,3% maior relativamente ao emprego de fluxos constantes, além de uma melhor linearidade da curva analítica; entretanto, o método mostrou-se susceptível a interferência de outros metilcarbamatos, o que comprometeu sua aplicação à análise de águas naturais. Na determinação de acidez total, a exploração de fluxos pulsados proporcionou menores variações da razão dos valores de absorbância relativos ao monitoramento do traçador e do indicador; não foi encontrada diferença estatística entre as titulações em fluxo propostas e o método titulométrico de referência ao nível de confiança de 95% / Multi-pumping flow systems use solenoid pumps as fluid propelling devices, which deliver pulsed flows. These flows provide an efficient radial mass transport, thus good mixing conditions even in limited sample dispersion situations. The main objective of this work was then to compare the performance of methodologies involving immobilized reagents in flow systems with constant or pulsed flows. To this end, the spectrophotometric determinations of ascorbic acid in pharmaceutical products using a 50-cm polyethylene tubular reactor with immobilized MnO2(s) with further colour-forming reaction with 0.25 mol L-1 formaldoxime; and carbaryl in natural waters exploiting liquid-liquid extraction with xylene immobilized in a PVDF membrane and a 0.1 mol L-1 ¬¬NaOH solution as acceptor stream, were selected. Moreover, constant and pulsed flows were compared in relation to a novel strategy for flow titration, named tracer-monitored titration; the determination of total acidity in vinegars was selected and flow injection and triangle-programmed titrations were applied, both using a 0.01 mol L-1 NaOH solution as titrant, phenolphtalein as acid-base indicator and ca. 6 mg L-1 brilliant blue FCF as tracer. Regarding ascorbic acid determination, the pulsed flow system was superior in relation to the constant flow system for detection limit: 0.33 against 0.60 mg L-1 (3.3 ? criterion), and for repeatability: r.s.d. estimated as 2.5 against 5.6% (n = 20); in relation to accuracy, no significant differences between the proposed method and that of the British Pharmacopoeia were found at the 95% confidence level. Regarding carbaryl determination, use of pulsed flows favored the analyte extraction, leading to a 9.3% sensitivity improvement in relation to use of constant flows; besides the attainment of better linearity of the analytical curve. The method was however susceptible to interference of other methylcarbamates, thus the application to natural water analyses was impaired. Regarding total acidity determination, pulsed flows exploitation provided lower variations in the ratio of absorbance values related to the monitoring of tracer and indicator; no significant differences between the proposed titrations and the reference method were found at the 95% confidence level
105

Interfaces liquides / liquides actives : apport de l’optique non linéaire et de la tensiométrie / Active Liquid/liquid Interfaces : contributions of non linear optics and tensiometry

Gassin, Pierre-Marie 21 June 2013 (has links)
Dans le cadre de la séparation sélective pour le traitement et la valorisation des combustibles nucléaires usés, l’extraction liquide/liquide est largement utilisée au niveau industriel. Néanmoins, ce procédé est encore mal compris en ce qui concerne les phénomènes physico-chimiques qui se produisent à l’interface liquide/liquide. Ce travail porte sur la compréhension de la dynamique de l’interface liquide nanométrique durant le transfert d’une espèce entre une phase aqueuse et une phase organique. Deux techniques expérimentales ont principalement été utilisées: la mesure de tension interfaciale et l’optique non linéaire. Ce travail a également donné lieu au développement d’un modèle numérique de dynamique de transfert de phase prenant en compte à la fois des phénomènes de transport diffusif proche de l’interface et une cinétique chimique sur l’interface décrivant les processus d’adsorption/désorption. Des systèmes modèles constitués de molécules surfactantes et/ou chromophores et/ou complexantes ont été étudiés aux interfaces air/liquide et liquide/liquide. L’adsorption/désorption, l’agrégation en surface, la complexation d’ion à une interface liquide et la structuration des systèmes ont ainsi pu être étudiées tant d’un point de vue des états d’équilibre que de la dynamique. Enfin, ces études ont été appliquées à un système d’intérêt industriel utilisé dans le procédé de dépollution DIAMEX / Liquid-liquid extraction processes are widely used in the industrial fields of selective separation. Despites its numerous applications, the microscopic mechanisms which occur during a liquid liquid extraction processes are really unknown specially at the liquid/liquid interface. Thus, this work deals on the understanding of the phenomena which drive the mass transfer across a liquid/liquid interface. Two experimental techniques were used in this work: dynamic interfacial tension measurement and non-linear optical experiments. Along with the use of this experimental approach, a numerical model describing the mass transfer dynamic has been developed. This model works under the assumption that both diffusion and a chemical step describing adsorption and desorption processes contribute to the global transfer kinetics. Model systems of surfactant molecules, chromophore molecules and complexing molecule were investigated at liquid/liquid and air/liquid interface. Interfacial phenomena like adsorption, surface aggregation and ion complexing were studied. Finally, the methodology developed in this work was applied to studied an extractant molecule with potential industrial application
106

Synthèse et coordination de dérivés calixarène et de thiacalixarène en conformation 1,3-alternée / Synthesis and coordination of calixarene and thiacalixarene derivatives in 1,3-alternate conformation

Noamane, Mohamed Habib 13 December 2013 (has links)
Les récepteurs moléculaires sont des architectures maintenues par des liaisons covalentes et capables de fixer sélectivement des substances (ioniques et/ou moléculaires) au moyen d’interactions intermoléculaires diverses, aboutissant ainsi à la formation d’un assemblage d’au moins de deux espèces nommé complexe moléculaire. Au cours de ce travail, des stratégies de synthèse de dérivés de calix[4]arène et de son analogue thiacalix[4]arène en conformation 1,3-alternée ont été mises au point. Ces composés ont été fonctionnalisés par des groupements pyridine, catéchol, imidazole, pyrazole et pour la première fois oxamate. Les composés obtenus ont été caractérisés à la fois en solution par RMN et à l’état cristallin. Les propriétés complexantes vis-à-vis des métaux de transition en solution sont présentées. Pour certains dérivés, le pouvoir extractant envers les métaux de transition a été étudié et discuté. Enfin, la formation de réseaux de coordination à l’état cristallin par auto-assemblage de dérivés de calixarène ou de thiacalixarène et le cation argent est présentée et commentée. / Molecular receptors are preorganised architectures held by covalent bonds and capable of binding selectively ionic and / or molecular substrates via various intermolecular interactions, leading to the formation of molecular complexes composed of at least two species.In this work, the synthesis of a library of calix[4]arene and its analogue thiacalix[4]arene in 1,3-alternate conformation based ligands and tectons has been investigated. These two types of platforms have been equipped with pyridine, catechol, imidazole, pyrazole and, for the first time, oxamate units as coordinating sites. All compounds prepared were characterized in solution and in some cases in the crystalline state. Their binding propensity in solution towards transition metals has been determined and discussed. For some derivatives, their metal extracting properties have been investigated and presented. Finally, the formation of extended periodic architectures of the coordination network type in the crystalline state by self-assembly of calixarene based tectons and silver cation was achieved and presented.
107

Extraction d'un acide organique à partir de co-produits issus de l'industrie de la canne à sucre / Extraction of carboxylic acid from sugar cane industry by-products

Pislor, Emilie 05 July 2011 (has links)
La canne à sucre est une plante sucrière dont le jus contient des molécules naturelles pouvant être valorisées comme l’acide aconitique. Cet acide, présent en grande quantité dans le jus de canne, se retrouve tout au long du procédé sucrier et dans les co-produits issus de cette industrie. Dans le cadre du projet V2ARUN, il a été envisagé d’extraire l’acide aconitique à partir d’un des co-produits issus de l’industrie de sucrière de La Réunion. La précipitation, l’extraction liquide-liquide et les résines échangeuses d’ions sont les trois techniques d’extraction envisageables pour récupérer l’acide aconitique à partir de mélasse ou de vinasse issues de l’industrie sucrière réunionnaise. Suite à une comparaison de ces trois techniques d’extraction, il a été choisi de récupérer l’acide aconitique par chromatographie sur résines échangeuses d’ions à partir de vinasse de distillerie, car ce co-produit n’est pas encore valorisé à La Réunion. Deux résines anioniques ont été retenues pour cette extraction. Après avoir identifié les mécanismes de fixation de différents acides carboxyliques sur ces résines en réacteur agité, des essais sur colonne ont été réalisés et une proposition de procédé d’extraction d’acide aconitique à partir de vinasse sur une résine faiblement anionique a été élaborée. / Sugar cane juice contains lot of natural molecules which can be recovered, such as saccharose or carboxylic acids. The aconitic acid, which is the predominant molecule besides sugar, is found throughout sugar process and into by-products from sugar cane industry of La Reunion Island, has been considered. Precipitation, liquid-liquid extraction and ion exchange resins are three possible extraction process to recover carboxylic acid from molasse and distillery stillage (vinasse) coming from La Reunion sugar industry. After studying this three extraction process, the choice has been made to recover aconitic acid from vinasse by ion exchange resins. This by-product has been chosen because it is still not promoted in La Reunion Island. Amongst height ion exchange resins tested, two anionic resins showed better performance to recover aconitic acid from this by-product. The fixation mechanisms of different carboxylic acids onto those two resins have been identified using aqueous solutions of lactic, malic, citric and aconitic acids. Some column experiments of aconitic acid extraction from sugarcane vinasse have been done on laboratory scale with the two anionic resins and on semi-industrial scale with the weakly anionic resin. Finally, a complete aconitic acid extraction process has been proposed.
108

Déformulation de matrices complexes : vers une méthodologie raisonnée adaptée aux matrices issues des procédés de valorisation de la biomasse / Reverse engineering on complex matrices : towards a rationalized methodology dedicated to biomass conversion samples

Dubuis, Alexis 07 November 2019 (has links)
La conversion de la biomasse lignocellulosique en biocarburants et molécules biosourcées produit des matrices liquides complexes thermosensibles qui couvrent une large gamme de polarités et de masses moléculaires. Les outils analytiques développés dans la littérature donnent une description partielle de ces matrices oxygénées. Pour en comprendre la réactivité et mieux guider le développement des procédés de conversion, une meilleure caractérisation est nécessaire. L’objectif de cette thèse est de démontrer l’apport d’une dimension de fractionnement pertinente en amont de techniques séparatives pour accéder à la caractérisation à l’échelle moléculaire d’échantillons ex-biomasse. Une déformulation complète et structurée par familles chimiques est visée, sans perte ni modification des composés. Deux voies de fractionnement ont été investiguées : (1) fractionnement par solubilité à l’aide de l’extraction liquide-liquide (LLE) et de la chromatographie de partage centrifuge (CPC) et (2) fractionnement par taille avec la chromatographie d’exclusion stérique (SEC). Ces techniques se veulent complémentaires à une analyse par chromatographie liquide à polarité de phase inversée avec détection par spectroscopie ultraviolet-visible et spectrométrie de masse haute résolution (RPLC-UV/HRMS). Des méthodes de fractionnement LLE, CPC et SEC ont été développées sur molécules modèles afin d’identifier les mécanismes et la sélectivité chimique mis en jeu. Des cartographies 2D inédites ont ainsi été obtenues, assurant un gain important en pouvoir résolutif et une structuration nouvelle des chromatogrammes en comparaison à l’approche RPLC-UV/HRMS. Dans un second temps, le potentiel des couplages SECxRPLC-UV/HRMS et CPCxRPLC-UV/HRMS pour la description de matrices complexes a été illustré via l’étude de deux échantillons issus d’expérimentations en unités pilotes et de compositions chimiques très différentes, représentant deux voies possibles de transformation (biochimique et thermochimique) de biomasse lignocellulosique. La complémentarité entre les approches de séparation mises au point a ainsi permis de doubler le nombre de pics détectés tout en bénéficiant de l’organisation chimique des composés. Cette aide précieuse à l’identification a été renforcée par les informations structurales délivrées via les différents modes de détection, en particulier l’HRMS. La compréhension de la structuration des cartographies 2D a été présentée et discutée afin de proposer la stratégie la plus adaptée pour déformuler complètement un échantillon en s’appuyant sur la mesure de descripteurs pertinents. Enfin, l’une des approches développée dans cette thèse a été mise en œuvre pour l’isolement sélectif et l’élucidation structurale de molécules clefs au sein d’une matrice complexe à l’aide d’expériences en fragmentation MS et spectroscopie de résonance magnétique nucléaire (RMN) / The conversion of lignocellulosic biomass into biofuels and biosourced molecules produces complex thermosensitive liquid matrices which cover a wide range of polarity and molecular weight. Analytical tools developed in the literature only give a partial description of these oxygenated matrices. To understand the reactivity of these samples and optimize the development of conversion processes, a better characterization is required. The objective of this thesis is to demonstrate the interest of a relevant fractionation step prior to separation techniques to help the molecular characterization of biomass samples. The reverse engineering proposed for the sample is desired complete and chemically controlled (without loss or sample modification). Two fractionation pathways were investigated: (1) solubility fractionation with liquid-liquid extraction (LLE) and centrifugal partition chromatography (CPC) and (2) size fractionation with size exclusion chromatography (SEC). These techniques intend to be complementary to reversed-phase liquid chromatography hyphenated to ultraviolet-visible spectroscopy detection and high resolution mass spectrometry (RPLC-UV/HRMS). LLE, CPC and SEC methods were developed on model molecules to understand mechanisms involved and control the chemical selectivity. 2D contour plots were obtained, improving the resolving power and structuring chromatograms in comparison with RPLC-UV/HRMS. Then, SECxRPLC-UV/MS and CPCxRPLC-UV/MS hyphenations were applied to describe two complex samples from different substrates produced on experimental pilot units from two possible conversion pathways of lignocellulosic biomass (biochemical and thermochemical). The complementarity of separation modes allows to double the number of peaks detected, benefiting from the chemical organization of compounds. This constitute a support to identification also enhanced by multi-detection which provide additional structural information on compound detected, especially HRMS. Chemical organization in 2D contour plots were presented and discussed to propose the most adapted strategy to fully fractionate a sample based on the measurement of relevant descriptors. Finally, one of the fractionation approach developed in this thesis was used to isolate and structurally elucidate key molecules of a complex sample through MS fragmentation experiments and nuclear magnetic resonance spectroscopy (NMR)
109

Tripodale Azaliganden - Ambivalente Rezeptoren für Kationen und Anionen

Wenzel, Marco 28 April 2008 (has links)
Das Ziel der vorliegenden Arbeit bestand in der Synthese von neuen funktionalisierten tripodalen Azaliganden auf Basis von Tris(2-aminoethyl)amin (Tren) und ihrer Charakterisierung als Rezeptoren und Extraktionsmittel für Kationen, Anionen sowie Salze. Die Komplexbildungs- und Phasentransfereigenschaften gegenüber den Kationen Ag(I), Co(II), Ni(II), Cu(II), Zn(II) und Cd(II) sowie den Anionen Cl-, Br-, I-, H2PO4-, SO42- und HCrO4- wurden durch Flüssig-Flüssig-Extraktion und Flüssigmembrantransport, 1H-NMR-Spektroskopie sowie Silberpotentiometrie untersucht; Struktur-Wirkungsbeziehungen für die jeweiligen Wirt/Gast-Systeme wurden abgeleitet. Röntgenkristallstrukturanalysen ausgewählter Komplexe mit den Kationen Ag(I), Ni(II) und Cu(II), den Anionen Br- und BF4- sowie dem Salz Hg(ClO4)2 ergänzten die gewonnenen Aussagen durch detaillierte Informationen zur Struktur und zu den auftretenden Wechselwirkungen. In die Betrachtungen wurden vergleichende Untersuchungen zur Ag(I)-Bindung durch strukturverwandte tripodale Schiffsche Basen einbezogen. Zusammenfassend wird der Einfluss der unterschiedlichen ligandspezifischen Charakteristika sowie der Substratspezies auf die Komplexbildung in Lösung und die Festkörperstruktur diskutiert. Die untersuchten tripodalen Aminverbindungen auf Basis von Tren zeigten in Abhängigkeit von ihrer Struktur ein differenziertes Extraktionsverhalten im System Metallsalz-Puffer-Wasser/Ligand-Chloroform. Als wesentliche Einflussfaktoren auf die Extraktion erwiesen sich Art, Anzahl und Anordnung der Donoratome sowie die differenzierte Lipophilie der Liganden. Die Zusammensetzung der extrahierten Komplexe in der organischen Phase ergab sich in den meisten Fällen zu 1:1 (Ag(I) : Ligand). Die bestimmte Reihe steigender Komplexstabilität für die 1:1-Komplexe von Ag(I) in Methanol unterstreicht in Analogie zu den Extraktionsuntersuchungen den Einfluss der Ligandcharakteristika auf die Komplexbildung. So führten Liganden mit tertiären Aminstickstoffatomen, zusätzlichen O-Donoratomen sowie sterisch anspruchsvollen Substituenten im Molekül zu geringeren Komplexstabilitäten, während zusätzliche S- und Pyridin-N-Donoratome in den untersuchten Aminverbindungen eine deutliche Steigerung der bestimmten Konstanten ergaben. Vergleichende Untersuchungen mit tripodalen Iminopodanden zeigten mit Ausnahme des 2-pyridylmethyl-substituierten Liganden generell niedrigere Stabilitäten der Ag(I)-Komplexe. 1H-NMR-Untersuchungen zur Komplexbildung in Lösung deuten unter veränderten Bedingungen auch auf einen möglichen Wechsel in der Komplexzusammensetzung und im Bindungsmuster für Ag(I) in Abhängigkeit von den im Molekül vorhandenen Donorfunktionen hin. Während für N4-Liganden ohne zusätzliche Donoratome sowie in Anwesenheit von S- und N-Donoratomen eine Zusammensetzung (Ag(I) : Ligand) von 1:1 bestimmt wurde, führen zusätzliche Pyridin-N-Donoratome zu einem stöchiometrischen Verhältnis von 3:2. Die Röntgenstrukturanalysen der Ag(I)-Komplexe von tripodalen Schiffschen Basen mit unterschiedlichen Substituenten unterstreichen die Variabilität der Koordinationsgeometrie von Ag(I) in Abhängigkeit vom Liganden. Interessant ist die Ausbildung von schwachen C-H···Ag-Wasserstoffbrücken in den Ag(I)-Komplexen der benzyl- und 4-biphenylmethyl-substituierten Liganden. Für die Kationen Co(II) und Zn(II) wurden mit den untersuchten Liganden generell nur geringe Extrahierbarkeiten erzielt. Dabei ist der Einfluss von Ligandstruktur sowie Lipophilie der Verbindungen auf die Extraktion stärker ausgeprägt als für Ag(I). Die Extraktion aus einem Gemisch von Co(II), Ni(II), Cu(II), Zn(II) und Cd(II) zeigte generell einen Anstieg der Extraktion in der Reihe Co(II) < Ni(II) < Zn(II) < Cd(II) < Cu(II). Lediglich die Verbindung mit einer OH-Funktion in 2-Position der aromatischen Substituenten führte zu höheren Extraktionsausbeuten für Co(II), Ni(II) und Cd(II) gegenüber Cu(II) und Zn(II). Röntgenstrukturanalysen von vier Cu(II)- bzw. Ni(II)-Komplexen veranschaulichen die bevorzugte höhere Koordinationszahl dieser Metallionen in relevanten Komplexen im Vergleich zu Ag(I). Die höhere Koordinationszahl wird dabei durch eine zusätzliche Koordination von Anionen oder Lösungsmittelmolekülen erreicht. Im Gegensatz zu den Kationen ist die Anionenextraktion wesentlich sensitiver gegenüber wechselnden experimentellen Bedingungen. Das hängt insbesondere mit den veränderten Bindungsverhältnissen in Anionenkomplexen zusammen. So wird die Extraktionsausbeute stark durch die Lipophilie der Liganden beeinflusst; ein signifikanter Anionentransport in die organische Phase wurde lediglich mit lipophilen Liganden erzielt. Die beobachtete Abstufung steigender Extraktion SO42- < Cl- < HCrO4- < I- ist in Übereinstimmung mit der zunehmenden Lipophilie dieser Anionen. In Abhängigkeit von der Natur der vorhandenen N-Donorfunktionen im Liganden und der Struktur der Liganden insgesamt wurde ein ausgeprägter pH-Einfluss auf die Extraktion der Anionen beobachtet. Während für die Liganden mit sekundären Aminfunktionen hohe Extrahierbarkeiten bei einem pH-Wert von ca. 5 auftraten, stiegen die Extraktionsausbeuten für Verbindungen mit tertiären Aminstickstofffunktionen mit abnehmenden pH-Wert kontinuierlich an. Die untersuchten Anionen wurden vorwiegend unter Bildung von 1:1- und 1:2-Komplexen (Anion : Ligand) in die organische Phase überführt. Für den Membrantransport war eine steigende Transportrate entsprechend der Dominanz der Lipophilie in der Reihe H2PO4- < SO42- < Cl- < Br- charakteristisch. Ein bevorzugter Transport von Cl- gegenüber Br- wurde hingegen mit sterisch anspruchsvollen Liganden sowie ausgeprägt lipophilen Verbindungen erreicht. Die Strukturen von zwei Anionenkomplexen mit BF4- bzw. Br- zeigen differenzierte Bindungsmuster. Einmal verhindern in einem Iminopodanden starke intramolekulare Wasserstoffbrücken zwischen dem protonierten Brückenstickstoff und den Iminfunktionen der Podandarme einen Einschluss des BF4--Anions in den vorliegenden Pseudokäfig, so dass die Koordination des Anions lediglich über schwache C-H···F-Kontakte an der Ligandperipherie erfolgt. Im Gegensatz dazu sind in einem N4-Aminliganden die drei Aminfunktionen der Podandarme protoniert. Die Br--Ionen werden sowohl durch ladungsunterstützte N-H···Br- als auch durch C-H···Br-Wasserstoffbrücken vom Liganden koordiniert. Weiterhin konnte in der Arbeit der Nachweis geführt werden, dass durch die Kombination von kationen- und anionenbindenden Funktionseinheiten in einem tripodalen Liganden die simultane Bindung und Extraktion von Kationen und Anionen möglich wird. Die Röntgenkristallstruktur eines Hg(ClO4)2-Komplexes bestätigt dabei die gleichzeitige Koordination von Kation und Anion durch die unterschiedlichen spezifischen Funktionseinheiten im Molekül.
110

Étude sur l'utilisation de liquides ioniques à base imidazolium pour l'extraction sélective de phosphopeptides

Sanon, Samantha Herntz 04 1900 (has links)
La phosphorylation des protéines constitue l’une des plus importantes modifications post-traductionnelles (PTMs) et intervient dans de multiples processus physiologiques tels, la croissance, la différenciation cellulaire, l’apoptose, etc. En dépit de son importance, l’analyse des phosphoprotéines demeure une tâche difficile en raison de leur nature dynamique (car la phosphorylation des protéines est un processus réversible) et de leur faible abondance relative. En effet, la détermination des sites de phosphorylation est souvent difficile car les phosphopeptides sont souvent difficiles à détecter par des méthodes d’analyse chromatographique classique et par spectrométrie de masse (MS). De récentes études ont démontré que les nombreuses méthodes d’enrichissement de phosphopeptides existantes ne sont pas complètes, et que le nombre total de phosphopeptides détectés ne chevauchent pas complètement ces méthodes. C’est pour cela qu’il existe une nécessité de combler les lacunes des méthodes d’enrichissement existantes afin d’avoir des analyses phosphoprotéomiques plus complètes. Dans cette étude, nous avons utilisé les liquides ioniques (LI), plus particulièrement les sels d’imidazolium, comme une technique d’enrichissement alternative, dans le but de favoriser une extraction sélective de phosphopeptides présents en solution. Les sels d’imidazolium ont donc été utilisés en raison de leurs propriétés physico-chimiques "facilement" ajustables selon la nature des substituants sur le noyau imidazolium et la nature de l’anion. Les sels de monoimidazolium et de bis-imidazolium possédant respectivement des chaînes linéaires à 4, 12 et 16 atomes de carbone et ayant différents anions ont été synthétisés et utilisés pour effectuer des extractions liquide-liquide et solide-liquide des phosphopeptides en solution. Dans un premier temps, des extractions liquide-liquide ont été réalisées en utilisant un liquide ionique (LI) ayant une chaine linéaire de 4 atomes de carbone. Ces extractions réalisées avec le bis(trifluoromethanesulfonyl) amide de 3-butyl-1-methylimidazolium (BMIM-NTf2) et l’hexafluorophosphate de 3-butyl-1-methylimidazolium (BMIM-PF6) n’ont pas montré une extraction notable du PPS comparativement au PN. Dans un deuxième temps, des extractions solide-liquide ont été réalisées en fonctionnalisant des particules solides avec des sels d’imidazolium possédant des chaines linéaires de 12 ou 16 atomes de carbone. Ces extractions ont été faites en utilisant un phosphopentapeptide Ac-Ile-pTyr-Gly-Glu-Phe-NH2 (PPS) en présence de 2 analogues acides non-phosphorylés. Il a été démontré que les sels d’imidazolium à chaine C12 étaient meilleurs pour extraire le PPS que les deux autres peptides PN (Ac-Ile-Tyr-Gly-Glu-Phe-NH2) et PE (Ac-Glu-Tyr-Gly-Glu-Phe-NH2) L’électrophorèse capillaire (CE) et la chromatographie liquide à haute performance couplée à la spectrométrie de masse (LC-MS) ont été utilisées pour quantifier le mélange des trois peptides avant et après extraction ; dans le but de mesurer la sélectivité et l’efficacité d’extraction de ces peptides par rapport à la composition chimique du liquide ionique utilisé. / Protein phosphorylation is one of the most important post-translational modifications because it is involved in multiple physiological processes such as growth, differentiation, apoptosis, etc. Despite its importance, the analysis of phosphoproteins remains a difficult task due to their dynamic nature (phosphorylation of proteins is a reversible process) and their low abundance. Indeed, the determination of phosphorylation sites is difficult because phosphopeptides are often difficult to detect by conventional chromatographic analysis and by mass spectrometric (MS) methods. Recent studies have shown that the existing methods of enrichment of phosphopeptides are not complete, and the total number of phosphopeptides detected does not overlap completely with those detected by these methods. The gaps in existing enrichment methods need to be filled in order to have more complete phosphoproteomic analyses. In the current study, ionic liquids (IL), specifically imidazolium salts, have been used in an alternative enrichment technique with potential for selective extraction of phosphopeptides from solution. Imidazolium salts were chosen because their physicochemical properties are readily adjustable depending on the nature of the substituent attached to the imidazolium core and the counter-anion. Monoimidazolium and bis-imidazolium salts with linear chains having respectively 4, 12, and 16 carbon atoms and with different anions were synthesized and used to carry out liquid-liquid and solid-liquid extractions of a phosphorylated peptide from a solution. At first, liquid-liquid extractions were carried out using an ionic liquid (IL) with a linear chain of 4 carbon atoms. These extractions performed with bis (trifluoromethanesulfonyl) amide 3-butyl-1-methylimidazolium (BMIM-NTf2) and hexafluorophosphate 3-butyl-1-methylimidazolium (BMIM-PF6) did not show a considerable extraction of PPS comparatively to the PN. Secondly, solid-liquid extractions were done by first functionalizing solid-phase particles with the imidazolium salts. The extractions were carried out using the phosphopentapeptide Ac-pTyr-Ile-Gly-Glu-Phe-NH2 (PPS) and its acidic non-phosphorylated analogues. It has been shown that the C12 chain imidazolium salts were better to extract PPS than the other two peptides PN (Ac-Ile-Tyr-Gly-Glu-Phe-NH2) and PE (Ac-Glu-Tyr-Gly-Glu-Phe-NH2). The extraction efficiency of these peptides was estimated by capillary electrophoresis (CE) and high performance liquid chromatography coupled with mass spectrometry (LC-MS).

Page generated in 0.1184 seconds