Tesis sobre el tema "Extractive capital"
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Gilbert, Paul Robert. "Money mines : an ethnography of frontiers, capital and extractive industries in London and Bangladesh". Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/60593/.
Rizek, Maytê Benicio. "Efeitos da exposição ao mercado de produtos florestais não madeireiros sobre o capital social de comunidades extrativistas da Amazônia brasileira". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/90/90131/tde-03112010-015234/.
The belief in the capacity of Non Timber Forest Products (NTFPs) to reconcile the double aim of providing for the well-being of extractive communities and conserving tropical forests resulted in the implementation of various programs with this purpose in the Brazilian Amazon. Among these programs it is increasingly common the adoption of partnerships between extractive communities and companies to trade NTFPs. Recently, however, several studies have highlighted the shortcomings of trading NTFP, regarding both biological conservation and the well-being of communities. Within the context of well-being impacts, there is a fear the increased integration of largely autarkic communities into NTFP markets can disrupt cooperation strategies and sharing practices, which have economic and social functions to peasant economies, particularly for more vulnerable households. In this study, we focus on this issue and advance the hypothesis that increased trade in NTFP may disrupt those cooperative institutions, bringing negative consequences to the security of the most economically vulnerable subgroups. To test this hypothesis, we compare two communities of the Médio Juruá Extractive Reserve, Brazilian Amazonia, which share the same historical background and similar environmental and geographic conditions, but differ in relation to NTFP trade. While Roque community trades vegetable oils with cosmetics companies, Pupuaí carries on with previous economic practices. Data gathering techniques included random systematic observations, household surveys, participatory rural appraisal and structured and semi-structured interviews. The results indicate that the community integrated into NTFP markets has fewer cooperative events than the community less market integrated. Despite that, no pattern is observed when we compare the association between levels of market participation among households. Therefore, we concluded the hypothesis was only partially accepted, because the changes in sharing practices are observable only at the community level. When we evaluate the effects of cooperation networks on more vulnerable households, we find two main results. First, we find a different pattern between the two communities as regards vulnerable households. While more vulnerable households benefit more from cooperative events in the community integrated into NTFPs, the opposite is observed in the community less exposed to markets. Even so, because the frequency of cooperation is much lower in the community trading NTFPs, these differences mean more vulnerable households still get fewer payoffs from cooperation than in the community less market integrated. Secondly, households from the community trading NTFPs, besides cooperating less frequently, also do so with a smaller number of different households when compared with the community less integrated to markets, which means their networks of social capital are weaker. It is therefore not yet clear in which community the human needs of vulnerable households are better fulfilled in order to ascertain whether the reduction on cooperative behavior diminishes their well-being.
Lisi, Cosimo. "Paris et l'origine coloniale de la ville contemporaine : accumulation primitive, production de l'espace, pratiques artistiques, production de subjectivité (XIXe et Xxe siècles)". Electronic Thesis or Diss., Paris 8, 2022. http://www.theses.fr/2022PA080012.
In this research, I genealogically trace the progressive emergence of an articulation between artistical-cultural production and capitalist pro- duction in the urban shaping of Paris. I retain a long time (19th and 20th centuries) . At first, I consider how the early 2000s smart city model ab- sorbed and domesticated the radical claim by 1960s aesthetic movements to overcome art as a contemplative relationship. Whereas those move- ments posited the intimate connection between aesthetic and social pro- duction, the city following the capitalist restructuration present itself as a« fantasmagoric » unity. I then retrieve the deep conflicts structuring such apparent unity showing how contemporary urbanscape directly reorgan- ized colonial technologies, such as cartography and identification. The colonial matrix of urban governance highlights that segregating policies are at the heart of the aesthetic model of structuring both social partici- pation and neo-colonial exclusion within the contemporary urban space. Continuous primitive accumulation is a reading key of the process taken into consideration
Taylor, Grantley J. "Determinants of financial instrument disclosure patterns of Australian listed resource firms pre- and post-IFRS adoption". Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/516.
Mack, Andrew Robert. "Rethinking the dynamics of capital accumulation in colonial and post-colonial Indonesia: Production Regulation". Thesis, The University of Sydney, 2001. http://hdl.handle.net/2123/498.
Mack, Andrew Robert. "Rethinking the dynamics of capital accumulation in colonial and post-colonial Indonesia: Production Regulation". University of Sydney. Political Economy, 2001. http://hdl.handle.net/2123/498.
Quintana, Ashwell Nicolas Efrain. "Essays on optimal extraction of groundwater in Western Kansas". Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38153.
Department of Agricultural Economics
Jeffrey M. Peterson
Nathan P. Hendricks
The two studies presented in this dissertation examine incentives for groundwater extraction and their resulting effect on aquifer depletion. Both studies apply dynamic optimization methods in a context of irrigated agriculture in arid and semi-arid regions such as in western Kansas. The first study examines the effects of capital subsidies aimed at increasing irrigation application efficiency. The second study examines the effects of changing incentives posed by changes in climatic patterns and by technical progress in the form of increasing crop water productivity. Both studies have significant policy and groundwater management implications. Subsidies for the adoption of (more) efficient irrigation technologies are commonly proposed and enacted with the goal of achieving water conservation. These subsidies are more politically feasible than water taxes or water use restrictions. The reasoning behind this type of policy is that increased application efficiency makes it possible to sustain a given level of crop production per acre with lower levels of groundwater pumping, all else equal. Previous literature argues that adoption of more efficient irrigation systems may not reduce groundwater extraction. Rewarding the acquisition of more efficient --and capital intensive-- irrigation equipment affects the incentives farmers have to pump groundwater. For instance, the farmer may choose to produce more valuable and water intensive crops or to expand the irrigated acreage after adopting the more efficient irrigation system. Hence, the actual impact of the policy on overall groundwater extraction and related aquifer depletion is unclear. The first chapter examines the effects of such irrigation technology subsidies using a model of inter-temporal common pool groundwater use with substitutable technology and declining well-yields from groundwater stocks, where pumping cost and stock externalities arise from the common property problem. An optimal control analytical model is developed and simulated with parameters from Sheridan County, Kansas-- a representative region overlying the Ogallala aquifer. The study contrasts competitive and optimal allocations and accounts for endogenous and time-varying irrigation capital on water use and groundwater stock. The analysis is the first to account for the labor savings from improved irrigation technologies. The results show that in the absence of policy intervention, the competitive solution yields an early period with underinvestment in efficiency-improving irrigation technology relative to the socially efficient solution, followed by a period of over-investment. This suggests a potential role for irrigation capital subsidies to improve welfare over certain ranges of the state variables. In contrast to previous work, the findings are evidence that significant returns may be achieved from irrigation capital subsidies. Finally, a policy scenario is simulated where an irrigation technology subsidy is implemented to explore whether such a program can capture significant portions of the potential welfare gain. Results indicate that the technology subsidy can improve welfare, but it captures a relatively small portion of the potential gains in welfare. The second chapter presents a dynamic model of groundwater extraction for irrigation where climate change and technical progress are included as exogenous state variables-- in addition to the usual state variable of the stock of groundwater. The key contributions of this study are (i) an intuitive description of the conditions under which groundwater extraction can be non-monotonic, (ii) a numerical demonstration that extraction is non-monotonic in an important region overlying the Ogallala Aquifer, and (iii) the predicted gains from management are substantially larger after accounting for climate and technical change. Intuitively, optimal extraction is increasing in early periods when the marginal benefits of extraction are increasing sufficiently fast due to climate and technical change compared to the increase in the marginal cost of extraction. In contrast, most previous studies include the stock of groundwater as the only state variable and, consequently, recommend a monotonically decreasing extraction path. In this study, the numerical simulations for a region in Kansas overlying the Ogallala Aquifer indicate that optimal groundwater extraction peaks 23 years in the future and the gains from management are large (29.5%). Consistent with previous literature, the predicted gains from management are relatively small (6.1%) when ignoring climate and technical change. The realized gains from management are not substantially impacted by incorrect assumptions of climate and technical change when formulating the optimal plan.
Gómez, Andrés. "Resisting abandonment: An ethnography of oil workers' resistance to political violence and capital accumulation in rural Colombia". Thesis, Uppsala universitet, Institutionen för kulturantropologi och etnologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-277715.
Lee, Angela. "Seeding Sustainability Over Extracting Capital: Advancing a Vision for Technology Justice in the Canadian Agri-Food Sector". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42003.
Barreto, Joana Correia. "Financial debt determinants of United Kingdom's crude petroleum extraction companies: an empirical investigation". Master's thesis, Instituto Superior de Economia e Gestão, 2010. http://hdl.handle.net/10400.5/2394.
The main purposes of this research are to test the importance of capital structure determinants (firm size, profitability, liquidity, non-debt tax shields and asset specificity) and to demonstrate their contribution when applied to leverage measures (total debt, short-term debt and long-term debt). An empirical examination of financial data related to United Kingdom's crude petroleum extraction companies during the five years period 2003-2007 was made, modelling the debt ratios as functions of company specific attributes hypothesized by capital structure theories. Using linear regression models, the results achieved demonstrate that: (i) the profitability extensively influence the capital structure of U.K.'s crude petroleum extraction firms; (ii) the results on firm size variable confirmed to be relevant for the leverage explanation (computed as total debt and long-term debt) and indicate that the larger the firm the higher the leverage it is able to achieve and maintain; (iii) the non-debt tax shields results have proven to be aligned with the ones frequently reached since the coefficient obtained is negative for total debt and short-term debt; however, they are only significant for the short-term debt model; and (iv) liquidity and asset specificity are not significant for the measures of leverage explanation.
O presente trabalho tem como principais objectivos aferir a importância dos determinantes da estrutura de capital (dimensão da empresa, rentabilidade, liquidez, poupança fiscal não associada ao endividamento e especificidade dos activos) e demonstrar a sua relevância na explicação dos rácios de endividamento. Foi empiricamente analisada a informação financeira de um conjunto de empresas britânicas, pertencentes ao sector de extracção de petróleo bruto, para o período temporal de 2003 a 2007. As medidas de endividamento foram constituídas como funções que os diversos factores específicos das empresas, enumerados pelas teorias relativas à estrutura de capital, deveriam explicar. Recorrendo a modelos de regressão linear, os resultados alcançados permitem retirar as seguintes conclusões: (i) a rentabilidade influencia a estrutura de capital das empresas de extracção de petróleo bruto do Reino Unido; (ii) os resultados relativos à dimensão da empresa confirmaram a sua relevância para a explicação dos rácios de endividamento total e de longo prazo e indicam que quanto maior a empresa, maior o endividamento que a mesma consegue atingir e manter; (iii) a poupança fiscal não associada ao endividamento apenas influencia significativamente a dívida de curto prazo; contudo os coeficientes obtidos para a dívida total e de curto prazo estão ambos de acordo com a teoria académica uma vez que se apresentam com sinal negativo; e (iv) a liquidez e a especificidade dos activos não parecem ser factores relevantes na explicação da estrutura de capital das empresas de extracção de petróleo bruto do Reino Unido.
Banoub, Daniel. "The problem of fluctuation : nature, capital, and measure in Newfoundland's saltfish industry, 1887-1937". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-problem-of-fluctuation-nature-capital-and-measure-in-newfoundlands-saltfish-industry-18871937(19f5d22f-da42-4ec2-ad49-e9565f4ecff6).html.
Lemaître, Sophie. "Le droit à l'épreuve du flux financiers illicites dans le secteur extractif : entre manipulation et double discours". Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1G033.
Oil, gas and minerals are indispensable resources for our economies and are sought-after. They are particularly prone to illicit financial flows such as corruption, tax avoidance and money laundering. Awareness of the extent of illicit practices in the extractive sector is relatively new. Over the last two decades, various measures have been adopted, forming an ambitious legal framework to combat illicit financial flows in the extractive sector. Despite the existence of this legal framework, illicit practices are still persistent. Stakeholders within the extractive sector such as companies and public officials have been able to adapt and be creative in order to abuse, circumvent and manipulate this legal framework in order to preserve their advantages and perpetuate illicit financial flows. They can also use legal and financial engineering, which provides them with an arsenal of legal tools and mobilizes experts who master the legal, political and financial environment in which companies and public officials evolve. Hence while wanting to combat illicit financial flows, law can find itself propitious to these illicit practices and even to their service
Prá, Valéria Dal. "Brassica oleracea var. capitata: EXTRAÇÃO, CARACTERIZAÇÃO QUÍMICA E ATIVIDADE BIOLÓGICA DE METABÓLITOS SECUNDÁRIOS". Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/5969.
The main objective of this work was to evaluate the antioxidant and antibacterial activities of extracts of Brassica oleracea var. capitata, obtained by supercritical CO2 and ultrasound-assisted extractions, as well as to carry out the characterization of these extracts using gas chromatography coupled with mass detector. For supercritical CO2, five extractions were performed to investigate the influence of pressure (10-25 MPa) and temperature (20-60°C) on the extraction yield, chemical composition and antioxidant activity towards peroxyl, superoxide and hydroxyl radicals. The highest extraction yield was 0.47% at 60 °C and 25 MPa. In the characterization of the extracts was possible to identify compounds like sulforaphane and iberin nitrile. All extracts showed antioxidant activity for the three radicals, although the highest activity for all radicals was obtained using the extract obtained at 60 °C and 25 MPa (run 2). For the ultrasound-assisted extraction were evaluated the effects of solvent concentration and temperature. The extracts obtained in the optimized extraction condition, were subjected to different hydrolysis conditions before use in biological assays. It was evaluated the antioxidant activity against DPPH, superoxide and peroxyl radicals, besides the antibacterial activity against S. aureus and E. coli. Both crude and hydrolyzed extracts were characterized by gas chromatography coupled with mass detector. The best condition for extraction was 30 ° C and 60% (w /v) of ethanol. All extracts showed antioxidant activity towards DPPH, superoxide and peroxyl radicals, but the use of hydrolyzed extracts improved considerably the antioxidant activities. Antibacterial activity was detected only in extracts hydrolysates Brassica oleracea var. capitata. The main contributions of this work were that the use of supercritical CO2 extraction to obtain bioactive compounds from Brassica oleracea var. capitata showed a promising alternative to conventional methods of extraction, since it allowed the extraction of compounds of interest in science and industry. Besides, in this work was demonstrated that the hydrolysis of extracts can increase the antioxidant activity of plant extracts.
O objetivo principal deste trabalho foi avaliar a atividade antioxidante e antibacteriana de extratos de Brassica oleracea var. capitata, obtidos a partir de extração supercrítica e extração por ultrassom, além de caracterizá-los por cromatografia gasosa acoplada à detector de massas. Para os compostos bioativos apolares de Brassica oleracea var. capitata, utilizou-se extração com CO2 supercrítico e avaliou-se o potencial antioxidante dos extratos. Foram realizadas cinco extrações para investigar a influência da pressão (10 - 25 MPa) e temperatura (20 - 60°C) no rendimento da extração, na composição química e na atividade antioxidante frente os radicais peroxila, superóxido e hidroxila. Obteve-se o maior rendimento de extração 0,47% a 60 °C e 25 MPa. Na caracterização dos extratos foi possível a identificação de compostos como sulforafano e iberin nitrila. Todos os extratos apresentaram atividade antioxidante para os três radicais, porém a maior atividade para todos os radicais foi o extrato obtido a 60°C e 25 MPa. Para os compostos bioativos polares, otimizou-se a extração assistida por ultrassom. Os extratos obtidos nas melhores condições de extração foram submetidos a diferentes condições de hidrólise, antes da sua utilização nos ensaios biológicos. Avaliou-se a atividade antioxidante, frente ao radical DPPH, superóxido e peroxila, além da atividade antibacteriana, frente a S.aureus e E.coli. Tanto os extratos brutos quanto os hidrolisados, foram caracterizados por cromatografia gasosa acoplada à detector de massas. A melhor condição de extração foi a 30ºC e 60% (m/v) de etanol. Todos os extratos apresentaram atividade antioxidante frente aos radicais DPPH, superóxido e peroxila, mas o uso de extratos hidrolisados melhorou consideravelmente a atividade antioxidante. Em relação à atividade antibacteriana, apenas uma amostra, que foi submetida à condição de hidrólise alcalina apresentou ação frente a E.coli. Uma das principais contribuições deste trabalho foi que a utilização de extração com CO2 supercrítico, para obtenção de compostos bioativos de Brassica oleracea var. capitata, mostrou ser uma alternativa promissora em relação aos métodos convencionais de extração, pois permitiu a extração de compostos com interesse científico e industrial. Além disso, foi demonstrado que a hidrólise dos extratos pode aumentar consideravelmente a atividade antioxidante de extratos vegetais em relação aos extratos brutos.
Yokoya, Jennifer Michiko Chauca. "Análise enantiosseletiva da fluvastatina em plasma por eletroforese capilar". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/60/60137/tde-22102013-162517/.
Nowadays, cardiovascular diseases are the main causes of death in Brazil and worldwide. Statins are considered the most effective and well tolerated agents for the excessive increase in cholesterol blood levels, or hypercholesterolemia. Fluvastatin (FLV), a hypolipidemic second generation drug belongs to statin drug class, and it is commercialized as a racemate, that is, a equimolar mixture of (+)-3R, 5S- FLV and (-)-3S, 5R- FLV. Moreover, literature describes that (+)-3R, 5S- FLV enantiomer activity is thirty times higher than its antipode, which justifies the importance and necessity of methods for the stereoselective analysis of drugs which possess one or more than one asymmetry centers. Thus, this work aims the extraction of FLV enantiomers from a biological matrix (plasma) using one of the electromigration techniques, the EKC. FLV analysis by EKC employed large volume sample stacking as sample on-column concentration technique using a fused-silica capillary with 50.0 cm effective length and 75 ?m internal diameter, 50 mmol L-1 sodium tetraborate buffer, pH 9,5 plus 20 mmol L-1 2-hydroxipropyl-?-cyclodextrin as a background electrolyte, voltage of +25 kV, temperature of 15ºC, with sample injected in hydrodynamic injection mode (0,5 psi for 30 seconds) and detection using a diode array detector set at 300 nm. The enantiomers resolution was achieved with a resolution value of 3.0, and efficiency of 255840 and 150056, migration times of 7.2 and 7.4 minutes for (+)-3R, 5S- FLV and (-)-3S, 5R- FLV, respectively. Supported liquid extraction was the chosen sample preparation procedure, with the addition of 0.5 mL of 0.1 mol L-1 pH 7.0 phosphate buffer to 0.5 mL of plasma, the mixture was applied to the column and allowed to wet for 15 minutes, 4 mL of ethyl ether was then applied to the top of the column, allowed to percolate by gravity and the eluted solvent was collected in an ambar tube, the solvent was submitted to evaporation under nitrogen flow and the residue was ressuspended for injection in the capillary electrophoresis equipment. The analytical method was validated covering selectivity, linearity, within-run and between-run precision and accuracy, limit of quantification, carry-over, matrix effect, dilution integrity and stability studies parameters. The racemization study was also performed. The results support that the analytical method is linear in the range of concentrations from 250 to 725 ng mL-1for each enantiomer, and the limit of quantification was 250 ng mL-1; the method is precise and accurate, with variation under 15%. Besides, no carry-over effect was observed, and both enantiomers showed to be stable under thaw and freeze cycles, short and long term stability studies, autosampler stability, and also no racemization was observed. Related to matrix effect, alternative procedures were employed sucessfully in case of analysis of lipemeic and hemolized matrices. So, this is the first bioanalytical method developed, fast and reliable, to quantify FLV enantiomers in plasma samples using EKC with SLE as sample preparation procedure.
Ajimura, Tatiana Okura. "Análise do mesilato de imatinibe em plasma empregando a eletroforese capilar". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/60/60137/tde-01122010-135234/.
Imatinib mesylate is an important tyrosine kinase inhibitor that has been used for the treatment of Chronic Myeloid Leukemia (CML). Despite the efficacy of imatinib therap, some cases of treatment resistance have been described. A number of mechanisms of resistance have been identified, which include innate or acquired mutations in the BCR-ABL gene, imatinib binding to 1- acid glycoprotein and altered imatinib pharmacokinetics. Imatinib is mainly metabolized by CYP 3A4, whose enzymatic activity presents a large inter-individual variability and is susceptible to induction or inhibition by numerous co-medications, environmental and dietary constituents. Therefore a given dose can yield very different circulating concentrations between patients. The major of methods available for the determination of imatinib in biological samples apply high performance liquid chromatography as analytical technique. However, in this work, we developed and validated a method by capillary electrophoresis for the determination of this drug in human plasma. The analysis was performed using a fused silica capillary (50 µm internal diameter x 46.5 cm total length, 38.0 cm effective length), a 50 mmol/L sodium phosphate buffer pH 2,5 as background electrolyte, hydrodynamic injection time of 20s (50 mbar), voltage of 30 kV, capillary temperature of 35°C and detection at 200 nm. Plasma samples pre-treatment involved liquid-liquid extraction with methyl-terc-butyl ether as extractor solvent. The analytical parameters investigated, linearity, precision, accuracy, recovery, limit of quantification, selectivity and stability, presented in accordance with the confidence criteria established in the literature. Furthermore the application of the method was performed in the analysis of plasma samples from CML patients undergoing treatment with imatinib.
Toss, Daniel. "Extração de compostos fenólicos de Butia capitata utilizando dióxido de carbono supercrítico". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/26003.
In this work it is investigated the application of supercritical fluid extraction to obtain phenolic compounds from Butia capitata, collected in southern Brazil. This plant, known popularly as butiá, is a native species in Argentina, Uruguay, Paraguay and Brazil. The edible fruits are popular and eaten raw or as liqueurs, jellies or jams. In recent studies, it is shown that phenolic compounds are present in the fruits of butiá. These compounds deserve attention because they have antioxidant activity, preventing cardiovascular disease and reducing the risk of cancer. There are different processes to obtain phenolic compounds from plant matrices, but many of them make use of organic solvents at high temperatures, which depreciates the extract value. In this study, it is used a clean technology, with carbon dioxide (CO2) as solvent in supercritical conditions. The CO2 is nontoxic and nonflammable that makes it a safer option than other solvents. Furthermore, in supercritical conditions the CO2 has favorable conditions for extraction, as high diffusivities and densities. A feature that should be emphasized is the possibility of using low temperatures in the extract, when compared to processes using liquid solvents, since the phenolic compounds are decomposed by high temperature. In the experiments only the dried pulp was used. The experimental design was developed to assess the influence of three process variables at three levels: pressure (150, 200 e 250 bar), temperature (40, 50 e 60°C) and cosolvent content (1, 3 e 5% of ethanol). The extracts were analyzed by high performance liquid chromatography (HPLC), in which the yields were expressed in terms of mg of the identified phenolic compounds by HPLC/100g of dried pulp and by the Folin-Ciocalteau method, with yields, as total phenolic compounds, expressed in mg of rutin equivalent/100g of dried pulp. It were identified five majority phenolic compounds by HPLC. Its highest concentrations were found in the conditions of 250 bar, 60°C and 5% of cosolvent. The identified compounds were chlorogenic acid (0,46mg/100g of dried pulp), ferulic acid (1,45mg/100g of dried pulp), rutin (3,47mg/100g of dried pulp), quercetin (0,90mg/100g of dried pulp) and kaempferol (1,93mg/100g of dried pulp). In terms of total phenolic compounds, the best conditions were 200 bar, 50°C and 5% of cosolvent, which resulted in 23,09mg of rutin equivalent/100g of dried pulp. Also, the antioxidant activity of the extracts was measured by scavenging of the DPPH• radical, by the IC50 method. The method provides the necessary amount of extract to scavenging 50% of the radial. As expected, the extract obtained in experimental run with the highest yield in CFT showed a higher antioxidant activity (17.4 mg / mL), followed by the experimental run with the highest yield in phenolic compounds isolated (56.1 mg / mL), and, with less activity, the extract obtained by organic solvent (80.0 mg / mL).
Fujiya, Neide Mitsue. "Investigação de modos de extração aplicados a plantas de uso fitoterápico e tópico". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-26122006-171227/.
The interest for plants of medicinal and cosmetic application demands methods with efficient extraction. Sample preparation is one of most important steps in the development of an analytic methodology in herbal preparation. The present work proposes methodologies for the analysis of the secondary metabolites in natural products, with emphasis in extraction procedures. The following plants were evaluated: soy (Glycine max), capsicum (Capsicum anuum), chamomile (Matricaria chamomilla), guaraná (Paullinia cupana), mate (Ilex paraguariensis) by the use of capillary electrophoresis. The first proposed method was applied to the determination of isoflavones in soy germ capsules from four different pharmaceutical laboratories. Peak assignment of unknown isoflavones in certain samples was assisted by hydrolysis procedures, migration behavior and UV spectra comparison. A study of the composition of metabolites and nutrients as flavonoids, organic acids, carbohydrates, cations, anions and fatty acids were evaluated in soy leaf. An easy, rapid method of extraction was performed for capsicnoids in Capsicum anuum by Matrix Solid Phase Dispersion (MSPD). Different solid phases C18, silica and florisil were tested. To guaraná different methodologies of extraction were tested (ultrasound, turrax) compared to exhaustive Soxhlet extract. The influence of operating parameters (temperature, time) on the extraction efficiency of chamomile by ultrasound was studied, compared extract by maceration and processing. The mixture of water and glycol was used.
Baciu, Tatiana. "Solid-phase extraction coupled in-line to capillary electrophoresis: determination of drugs of abuse in biological samples". Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/458371.
Junior, Osmar Antunes. "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". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-16122008-162344/.
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.
Suarez, Carlos Alfredo. "Estabilidade de espécies de arsênio em amostras biológicas acoplando cromatografia líquida ou eletroforese capilar com detectores atômicos". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/64/64135/tde-16092010-151341/.
Analytical procedures for extraction, separation and identification of arsenic species at ultra-trace levels in biological and environmental samples were investigated. Stability studies of arsenic species in sample extracts and standard solutions were carried out. Separation of arsenite, arsenate, monomethylarsonic and dimethylarsinic acids and also arsenobetaine were carried out by capillary electrophoresis or liquid chromatography. Determination of the separated arsenic species was accomplished by coupling the separation techniques to inductively coupled plasma mass spectrometry (ICP-MS) or atomic fluorescence spectrometry (AFS). Satisfactory resolution and sensibility were achieved by the coupled systems described. Extraction efficiency better than78% were achieved with water in an ultrasonic bath at the laboratory temperature (23-27°C). Whereas, stability of species in solutions stored in refrigerator at +4°C was efficient for aperiod up to one week. Micro-volumes of standards and sample solutions mixed in a sequential injector were prepared for arsenic speciation by capillary electrophoresis, aiming green chemistry. A time controlled micro-volume injector device for hydrodinamic injections was also developed. Finally, waste solutions from arsenic speciation analysis in a system with hydride generation were treated for arsenic and boron removal. Cloud point extraction for recovery of arsenic and hydrothermal mineralization of boron by calcium hydroxide were employed. Satisfactory removal of 80% of arsenic and 75% of boron from waste solution was achieved. These procedures allowed to reduce volumes of hazardous waste solutions
Catai, Ana Paula Formenton. "Avaliação das técnicas de microextração e eletroforese capilar em meio não aquoso (NACE) para determinação de antidepressivos em amostras de plasma para fins de monitorização terapêutica". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-12032012-083032/.
Therapeutic monitoring allows individualization of the dose regimen and has been indicated for the monitoring of well-established therapeutic intervals. In psychiatric disorders, most of the patients require that the plasmatic concentrations to be within a fixed range, so the disorders are kept under control and the adverse effects are acceptable. The aim of the therapeutic monitoring is ensure clinical effectiveness and minimization of adverse effects of drugs prescribed at the clinic. New trends in analytical chemistry have been directed towards simplification and miniaturization of analytical systems, and minimization of organic solvents and sample volume. In this work, analytical methodologies using microextraction techniques, such as stir bar sorptive extraction (SBSE) and microextraction by packed sorbent (MEPS), in conjunction with capillary electrophoresis in a nonaqueous background electrolyte (NACE) were developed for therapeutic drug monitoring of selective serotonin reuptake inhibitors (SSRIs: fluoxetine, sertraline, paroxetine and citalopram) in plasma sample of patients in therapy with SSRIs. First, the optimization of electrophoretic separation of the SSRIs was carried out to obtain simultaneous analysis of all antidepressants. Among the conditions evaluated (different background electrolytes in aqueous and nonaqueous medium, micellar electrokinetic capillary chromatography, and NACE), NACE-UV gave the best results. In the sequence, the optimization of the inherent variables of microextraction techniques (SBSE and MEPS)aiming analyses time minimization and increase of analytical sensibilitywas carried out. For SBSE/NACE methodology development the variables such as time of extraction, temperature of extraction, and matrix pH were optimized. For MEPS/NACE methodology the variables matrix pH and the volume of draw-eject cycles were optimized. Analytical validation was carried out in agreement with the norms of National Health Surveillance Agency (ANVISA) for both of the proposed methods, in different plasmatic concentrations, which completed the therapeutic interval. The developed methods (SBSE/NACE e MEPS/NACE) were compared to the reference method, using liquid-liquid extraction (LLE/NACE). Microextraction techniques, compared to LLE, gave the following advantages: reutilization of the extraction phase, fewer numbers of steps for extraction, reduction of sample volume, and less consumption of organic solvents. According to the evaluated validation parameters, the standardized methods SBSE/NACE and MEPS/NACE can be used in the analyses of antidepressants (SSRIs) in plasma sample for therapeutic drug monitoring purposes.
Costa, Ana Carolina de Oliveira. "Metodologias para determinação de fármacos, metabólitos e disruptores endócrinos em água de abastecimento público utilizando técnicas de separação em meio líquido (CE/UV, CE-MS, LC-MS/MS)". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-08112010-143525/.
This work presents the development and validation of analytical methods to investigate the presence of pharmaceutical compounds, their metabolites and endocrine disruptors in surface water using on line (stacking) and off line (solid phase extraction) sample clean up and enrichment strategies coupled to advanced separation techniques in liquid medium (capillary electrophoresis and liquid chromatography with UV detection and their hyphenation with mass spectrometry). In the first Chapter, general aspects on pharmaceuticals, products of personal care and endocrine disruptors are discussed as well as their origin and means of entry to the environment. Chapter 2 describes the development of a separation method for the determination of eight pharmaceuticals and endocrine disruptors substances with acidic character (diclofenac, bezafibrate, fenoprofen, ibuprofen, ketoprofen, naproxen, gentisic and salicylic acids) in a single run using capillary electrophoresis with on line sample enrichment (analyte stacking with large sample volume injection) in electrolytes composed of 30 mmol L-1 sodium tetraborate at pH 9.3 and 5 mmol L-1 Brij 35. The proposed method reached limits of detection between 2 µg L-1 (naproxen) and 80 µg mL-1 (ibuprofen). In Chapter 3, a CE separation method for the determination of nine pharmaceuticals and hormones with neutral and basic character (fluoxetin, trimethoprim, diazepam, carbamazepine, propranolol, clofibrate, fenofibrate, ethynylestradiol and estrone) was exploited. As preconcentration strategy, micelle stacking with large sample volume injection was performed. Limits of detection in the order of 9 µg L-1 were reached with electrolytes composed of 30 mmol L-1 phosphoric acid, 40 mmol L-1 sodium dodecylsulfate, 20% (v,v) acetonitrile and 0.1% (v,v) triethylamine. In Chapter 4, the physicochemical parameters associated with the solid phase extraction technique, such as sorbent type, breakthrough volume, elution volume, extraction cartridge rinse, among others, were evaluated. Optimum sample clean up and off line preconcentration conditions combined with the optimum on line preconcentration and separation conditions described in Chapters 2 and 3, for all substances under consideration, were applied to the analysis of real surface water samples collected at the Reservoir Billings (Sao Paulo state, Brazil). The combined method reached concentrations in the order of 500 ng L-1, with satisfactory recoveries (58 88%) for complex environmental matrices. In Chapter 5, a method for the analysis of alkyl p-hydroxybenzoates, substances used as preservatives in several products of personal care, was developed using capillary electrophoresis associated with on line (stacking with large volume injection) and off line (SPE) preconcentration strategies. The proposed method, which used 40 mmol L-1 glycine and 40 mmol L-1 triethylamine as electrolyte, was applied to the analysis of alkyl p-hydroxybenzoates in surface water, reaching 4 - 6 µg L-1 concentrations. Chapter 6 describes the development of a CE method for de analysis of linear alkylbenzene sulfonates (LAS) and homologues, surfactants commonly used in the composition of detergents of industrial and domestic use. As separation electrolyte, 60 mmol L-1 TRIS, 30 mmol L-1 HIBA, 15 mmol L-1 Brij 35 and 40% (v,v) acetonitrile was used. A solid phase preconcentration extraction step in C18 was employed and a total LAS concentration of 1.09 mg L-1 was found in a sample obtained from the effluent of a sewage treatment plant. In Chapter 7, a CE-MS (ion trap) method was developed for the analysis of cimetidine, propranolol, salbutamol, trimethoprim and methoclopramide in fortified surface water samples collected in the Reservoir Billings (Sao Paulo state, Brazil) and previously enriched by SPE (PS-DVB). The method reached concentrations of c.a. 40 µg L-1. Finally, in Chapter 8, a method based on high-performance liquid chromatography coupled with two different mass spectrometers: a triple quadrupole and a triple quadrupole with linear ion trap). Several pharmaceuticals were investigated in surface water samples collected from the Reservoir Billings (Sao Paulo state, Brazil). With the LC-MS/MS (triple quadrupole) system, carbamazepine was found in a non treated sample (just a filtration step prior to injection was performed) in a concentration level of 20 ng L-1. It is worth mentioning that for carbamazepine, a LOD of 400 fg L-1 was found, without any preconcentration sample treatment