Les recherches menées au cours de cette thèse constituent une première étape de développement de méthodes expérimentales de concentration de nanoparticules à l'aide de composants micro-nanofluidiques. L'objectif principal est donc d'explorer différentes architectures de systèmes micro-nanofluidiques où l'étape de concentration est effectuée par effet d'exclusion stérique et/ou ionique sous l'application d'un champ de pression et/ou électrique. Une attention toute particulière a été portée sur les méthodes de caractérisation, comprenant notamment les méthodes de particule Tracking Micro-PIV et de microscopie par fluorescence pour mesurer la répartition en nanoparticules et quantifier les facteurs de concentration. Le premier axe concerne la concentration de nanoparticules dans des architectures de type « Bypass ». Dans le cas de la filtration stérique, une modélisation par méthode de différence finie permet de prédire l'apparition d'une zone localisée où la concentration est d'une centaine à un millier de fois plus élevée que la concentration initiale après une heure d'opération. Des composants micro-nano fluidique en silicium ont été réalisés afin de mener une étude paramétrique. En accord avec le modèle proposé, cette étude montre que le nombre de Peclet est le paramètre déterminent dans le choix du design et des conditions d'expérimentations optimums. Concernant la préconcentration par effet électrocinétique, les expérimentations ont essentiellement consisté à explorer le phénomène d'ICP (Ion Concentration Polarisation) et d'appliquer cette technique pour la concentration de nanoparticules. Enfin le type de géométries « Bypass » a été testé sous différentes conditions. Ainsi, le couplage avantageux de phénomènes électro-hydrodynamiques tel que le « streaming potentiel » permet d'ouvrir la voie à des systèmes de préconcentration à actionnements manuels, rapides et très simples d'utilisation. Le deuxième axe d'étude est quant à lui dédié à la conception et l'utilisation de configuration micro-nanofluidique plus originales. Y sont notamment étudiés des systèmes à configuration radial offrant une meilleure stabilité lors des étapes de préconcentration électrocinétiques. Sur la base des performances et limitations des différents systèmes micro-nanofluidiques réalisés, le dernier chapitre est une mise en perspective des champs d'applications potentiels, notamment pour les laboratoires sur puces. / The researches conducted during this thesis consist in a first step for the development of experimental methods applied to the concentration of nanoparticles using micro-nanofluidic devices. The main aim is to explore different system architectures where the préconcentration step are achieved using steric and/or ion exclusion under the influence of a pressure and/or electric field. A special attention is directed toward the characterization methods including Micro-Particle Image Velocimetry micro-PIV and fluorescent microscopy to measure the nanoparticles repartition and to quantify the concentration folds. The first axis deals with the preconcentration of nanoparticles within « Bypass » like architectures. Concerning the steric filtration, a theoretical model using finite element method allows to predict the rising of a located preconcentration zone where the local concentration is enhanced 1000 fold as compared to the initial concentration after 1h of concentration operation. Silicon Micro-nanofluidic devices were fabricated in order to conduct a parametric study. According to the proposed theoretical model, this study shows that the Peclet number is a key parameter to choose the optimal design and experimental conditions. Concerning the electrokinetic preconcentration, the experiments mainly consisted in exploring the ICP phenomenon (Ion Concentration Polarization) and in using this technic to preconcentrate nanoparticles. Finally the Bypass geometry was tested in many conditions. Thus, the advantageous coupling of electro-hydrodynamic phenomena such as the so called “streaming potential” opens new ways to fast, simple and manual preconcentration systems suitable for LOC applications. The second axis is dedicated to the conception and utilization of original micro-nanofluidic configurations. Will also be studied radial micro-nanofluidic devices offering better stability during electrokinetic preconcentration. On the basis of the performances and limitations inherent to each systems, the last chapter will focus on the potential applications relative to LOC.

Orientador: Marco Aurelio Zezzi Arruda / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T21:48:44Z (GMT). No. of bitstreams: 1 Coelho_LucianaMelo_D.pdf: 3258414 bytes, checksum: bf5794c1897da59a91597510c34ed02a (MD5) Previous issue date: 2005 / Doutorado / Quimica Analitica / Doutor em Quimica

This diploma thesis deals with an optimization technique for the determination of semimetals in selected samples of food, which consists of sample digestion, preconcentration and detection of the elements. Preconcentration is usually chosen because these elements are contained in foods only in trace amounts, which are undetectable for some techniques. This work also made characteristics of semimetals, in terms of their functions in the body, of the occurrence in food and the consequences for the organism on their surplus or shortage. The chosen technique of preconcentration in this work was the preconcentration of titanium dioxide. When optimizing the techniques, however, was unlike the results published in literature, obtained low yield of elements sorbed on titanium dioxide, therefore the samples were measured by inductively coupled plasma mass spectrometry directly after their mineralization, wet digestion with low temperature. The results of this work indicate that the elements arsenic, boron and selenium are given technique detectable without preconcentration, whilst set germanium content in all samples failed, due to very low concentrations and therefore in these cases would be required preconcentration.

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Interest in microchip capillary electrophoresis (CE) is growing due to the rapid analysis times provided and small sample input requirements. However, higher-concentration samples are typically needed because of the small (~pL) detection volumes in these devices. I have made membrane-based protein preconcentration systems in capillary and microchip designs to increase the detectability of low-concentration biological samples. A photopolymerized ion-permeable membrane interfaced with a microchannel in poly(methyl methacrylate) (PMMA) formed the preconcentrator. When a voltage was applied between the sample reservoir and the ionically conductive membrane in a capillary-based system, R-phycoerythrin was concentrated more than 1,000 fold, as determined by laser-induced fluorescence measurement. An integrated system that combines analyte preconcentration with microchip CE has also been developed using two different fabrication methods: polymerization and solvent bonding. In both approaches, microchannels within the PMMA substrates were interfaced with an ion-permeable hydrogel. When an electrical potential was applied along the channel, greater than 10,000-fold preconcentration was achieved for R-phycoerythrin. Concentrated protein samples were also injected and separated in these integrated microdevices. Membrane-based protein preconcentration devices can significantly increase the concentration range of biological samples that can be analyzed by microchip CE.

Detection of disease specific biomarkers is of great importance in diagnosis and treatment of diseases. Modern bioanalytical techniques, such as liquid chromatography with mass spectrometry (LC-MS), have the ability to identify biomarkers, but their cost and scalability are two main drawbacks. Enzyme-linked immunosorbent assay (ELISA) is another potential tool, but it works best for proteins, rather than peptide biomarkers. Recently, microfluidics has emerged as a promising technique due to its small fluid volume consumption, rapidness, low fabrication cost, portability and versatility. Therefore, it shows prominent potential in the analysis of disease specific biomarkers. In this thesis, microfluidic systems that integrate monolith columns for preconcentration and on-chip labeling are developed to analyze several protein biomarkers. I have successfully fabricated cyclic olefin copolymer (COC) microfluidic devices with standard micromachining techniques. Monoliths are prepared in situ in microchannels via photopolymerization, and the physical properties of monoliths are optimized by varying the composition and concentration of monomers to achieve better flow and extraction. On-chip labeling of protein biomarkers is achieved by driving solution through the monolith using voltage and incubating fluorescent dye with protein retained in the monolith. Subsequently, the labeled proteins are eluted by applying voltages to reservoirs on the microdevice and detected by laser-induced fluorescence. Finally, automation of on-chip preconcentration and labeling is successfully demonstrated.

Heavy metals, despite their essential roles as minerals in biological systems, pose a significant threat to human health and the environment due to their toxic properties. Even at low concentrations, heavy metals such as lead, mercury, arsenic, and cadmium can cause adverse effects on humans and animals. Consequently, stringent regulations have been established to limit heavy metal concentrations in water resources. However, existing laboratory-based analytical methods for heavy metal detection are time-consuming, expensive, and require skilled personnel. The current detection limit required by several health organizations around the globe is below 10 ppb for Lead, Mercury, Chromium, and Arsenic. The current state of the art which can accomplish low levels of detection is either expensive to operate or incapable of achieving the required trace level sensing. This thesis aims to address the need for a simple, cost-effective, and portable method for detecting heavy metals in water. The thesis begins by reviewing the current state-of-the-art heavy metal sensing methods, highlighting their limitations and the requirement for sample preconcentration. Various preconcentration techniques are discussed, emphasizing their performance parameters and advancements in trace-level detection. Furthermore, the thesis identifies the gaps in current technology, particularly in the context of developing a reliable and user-friendly method for testing heavy metal concentrations in drinking and surface waters. The primary objective of this thesis is to develop a preconcentration-based colorimetric method for detecting heavy metals in water. This method aims to overcome the limitations of existing techniques by offering high sensitivity and a limit of detection below regulatory ranges without the need for complex equipment or extensive sample preparation. The thesis contributes to the advancement of the state-of-the-art by providing a simplified, portable, and efficient solution for in-line detection of heavy metal contamination in water resources. This has been achieved through the design and deployment of sensor utilizing a novel architecture, measuring heavy metal ions down to the sub ppb level. we were able to detect ions such as copper and Lead at concentrations below 0.5 ppb with a limit of detection (LOD) of 0.14 ppb. Overall, this thesis combines knowledge from the fields of analytical chemistry, sensor technology, and environmental science to address the pressing need for a practical and accessible method for monitoring heavy metal concentrations in water. By achieving this goal, the research will contribute to safeguarding public health and promoting sustainable water resource management. / Thesis / Doctor of Philosophy (PhD) / Heavy metals can be found naturally and are needed in small amounts for our bodies to function properly. However, many heavy metals are toxic and can cause serious health problems even at very low concentrations. These metals can contaminate water sources through activities like mining and improper waste disposal. Currently, detecting heavy metals in water requires expensive equipment and skilled experts in a laboratory setting. This process is time-consuming and not easily portable for on-site testing. The existing methods also have limitations such as low sensitivity or the need for complex procedures. This thesis aims to improve the way we detect harmful heavy metals in water. The goal of this thesis is to develop a simpler and more sensitive method for detecting heavy metals in water. The focus is on using color-changing dyes that react to the presence of heavy metal ions. However, these dyes often have detection limits higher than what is considered safe, so the thesis also explores ways to concentrate the samples to improve sensitivity. By addressing these challenges, the thesis aims to contribute to the development of a reliable and easy-to-use method for testing heavy metal concentrations in drinking and surface waters, helping to protect public health and identify potential sources of contamination.

There is great interest in miniaturized analytical systems for life science research, the clinical environment, drug discovery, biotechnology, quality control, and environmental monitoring and numerous articles have been written which predict the success of microfluidic based systems. It was demonstrated in this work that a microfluidic flow system could be quickly and easily manufactured in a research lab environment without the need for clean room facilities. The microfluidic device was created using polymethylmethacrylate, a CO2 laser and a standard oven. The device was designed, manufactured and ready for use within three hours. This work also investigated a chemiluminescent system which was intended for use in protease assays in the microfluidic device. This work also focused on the use of photoinitiated polymer monoliths, with immobilized tannic acid, as protein preconcentrators. The function of the monolithic devices was demonstrated by pumping low concentration solutions of BSA BODIPY® FL through the monolith. Both loading and elution were done using pressure. It was shown that BSA could be concentrated on and successfully eluted from the monolith. The elution volume for a 125 nl monolith was found to be 4 μl. Therefore an injection of a 60 μl sample of 1 x 10⁻⁹M BSA BODIPY ® FL gave rise to a concentration factor of 15. The pH optimum for the binding of BSA BODIPY ® FL was found to be pH 8.0 and the loading capacity of the tannic acid monolith was found to be 0.6 mg.ml⁻¹.

Hemimicelles and admicelles are well-investigated wonders in modern science; they are surfactant monolayers and surface adsorbed micelles, respectively. Capacitance measurements for monitoring the formation of dodecyl sulfate (DS) surfactant monolayer on positively charged gold substrates (planar gold) and the adsorbance of 2-naphthol onto DS surfactant monolayer were performed. The investigation of the electrical control of DS at various concentrations (4, 6, 16, and 32 mM) below and above the critical micelle concentration (CMC= 8 mM) on gold surfaces for analyte preconcentration, prior to chromatographic analysis, is presented. Charged ionic surfactants, such as DS, drawn to a surface of opposite charge (porous nickel substrates coated with gold) serve as a stationary phase to trap organic analytes. It is believed that these DS assemblies gain stability through surfactant chain–chain interactions. The attachment and the removal of the surfactant are controlled using an electric field. Due to the fact that the surfactantanalyte association is released by electrical control, organic solvents, which are used in conventional solid phase extraction, are not required, making this procedure environmentally friendly. Electrical Impedance Spectroscopy was used to investigate the formation of the DS layer and the preconcentration of 2-naphthol in the presence of an applied electric field. High performance liquid chromatography was used to determine 2- naphthol concentrations. Anthracene and 9-anthracenecarboxylic acid were substituted as additional test molecules as well. Presented are the results of the preconcentration of 2-naphthol, anthracene and 9-anthracenecarboxylic acid using the DS layer with various concentrations of sodium dodecyl sulfate on a gold electrode surface.

O cenário atual das commodities minerais tem obrigado as empresas de mineração a otimizar suas operações e buscar soluções inovadoras para manter a lucratividade desejada de suas minas, controlar os riscos envolvidos e garantir a sobrevivência do negócio. Neste contexto, com a menor disponibilidade de minérios de alto teor, os depósitos minerais remanescentes exigem a lavra e o beneficiamento de grande quantidade de massa por tonelada de metal produzido. Apesar de apresentarem um teor médio decrescente, estes depósitos frequentemente contêm regiões com minério de teor mais elevado incorporados às porções de baixo teor ou mesmo na massa estéril. Por melhor que seja o conhecimento das reservas, a lavra seletiva dessa massa de teor mais elevado é praticamente inviável operacionalmente. A forma mais eficiente de aproveitar estas reservas é por meio do processo de pré-concentração de minério por ore sorting (seleção/classificação de minério). O objetivo deste processo é remover, quanto antes possível, o material com teor não econômico. A consequência imediata é uma potencial redução dos custos de processamento e do consumo de água e energia para a mesma massa de metal produzido. Existem várias tecnologias aplicáveis em pré-concentração; este estudo é focado especificamente na apresentação e discussão dos impactos causados no empreendimento mineiro de Phu Kham (PanAust), a partir da instalação e utilização do equipamento de pré-concentração, bulk ore sorter. Este equipamento faz uso de um sensor de ressonância magnética, e tem por objetivo a separação de grandes volumes de estéril direto no transportador de correias totalmente carregado (in-pit ou correia de alimentação da usina), baseando-se nos teores medidos ou inferidos a partir de seu sensor. A pré-concentração com bulk ore sorter é fundamentalmente utilizada para aumentar a produtividade baseada na capacidade fixa da usina e atenuar os prejuízos causados pelas incertezas nas definições de teores da mina. Isto é, a partir da maior precisão no controle do teor, pode-se reduzir a diluição e a perda de minério oriundas da operacionalização e explotação das reservas minerais, controlar o teor de corte e o teor médio na alimentação da usina ou ainda separar os diversos tipos de minérios para serem tratados em diferentes rotas no processo de beneficiamento. Este trabalho estuda a viabilidade técnica e econômica da aplicação do bulk ore sorter na mina de Phu Kham, no Laos. Inicialmente a tecnologia de sorting é apresentada, juntamente com os sensores disponíveis e o sistema diversor. Os resultados econômicos foram avaliados a partir dos dados de produção da mina no ano de 2014. Sem a possibilidade da realização de estudos de amostragem, a variabilidade do minério foi estimada a partir da variância de dispersão, uma ferramenta geoestatística. A estimativa do desempenho da separação inclui os erros associados a leitura do sensor e do sistema diversor. Avaliações econômicas foram realizadas para diferentes cenários e demonstraram que o bulk ore sorter tem o potencial de aumentar a produção metálica e o lucro. Este sistema de pré-concentração permite a que apenas o material com valor agregado alimente a planta de beneficiamento. / The current scenario of mineral commodities has forced the mining companies to optimize their operations and look for innovative solutions to maintain the desired profitability of their mines, control the risks involved and ensure the survival of the business. In this context, with the depletion of high grade deposits, the remaining lower grade deposits require the mining and processing of larger volumes of material per tonne of product. These low grade deposits often contain a large proportion of barren gangue. The aim of pre-concentration is to remove this barren material at as coarse a particle size and as early in the process as possible. This has the potential to reduce processing costs, energy and water consumption and possibly ore transport requirements. There are several technologies that may be applicable for pre-concentration; this work looks specifically at bulk ore sorting. This involves the separation of a large volume of barren gangue from a fully loaded conveyor belt (in-pit or plant feed belt) based on the grade as measured or inferred from a sensor measurement. Bulk ore sorting may be used to increase the production rate through fixed plant capacity, or reduce the required size of downstream processing equipment. Uneconomic or marginal reserves may be upgraded making them economic to treat and improving the resource utilisation. Bulk ore sorting could also be used to reduce dilution and ore loss in mining operations by improving grade control, or to separate ore types to treat via different process routes. Thus, bulk ore sorting has the potential to improve the profitability and reduce the environmental impact of mining operations and may be applied in different ways. This study investigates three examples of how bulk ore sorting may be employed and the associated economic benefits. The technical and economic viability of bulk ore sorting is evaluated for a copper deposit in Laos. Bulk ore sorting technology is described briefly along with discussion of appropriate sensor and diversion systems for the copper deposit considered. The economic implications were evaluated using the actual mined material and costs from 2014 as the base-case. In the absence of sampling data, ore grade variability was estimated using geo-statistical tools based on mine grade control data. A process model of the sorter was developed considering the accuracy of the sensor measurement and errors associated with material diversion. This was used to simulate the separation performance. Economic evaluations were conducted for a number of different scenarios and demonstrated that bulk ore sorting has the potential to increase the amount of metal in product and annual profit for the operation considered. This is because it is cheaper to sort and reject below cut-off grade material contained in the plant feed than to treat this material through the processing plant. The sorter acts as a gatekeeper - only above cut-off grade material (value-adding) reports to the processing plant.