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On the reliability of methods for the speciation of mercury based on chromatographic separation coupled to atomic spectrometric detectionQvarnström, Johanna January 2003 (has links)
This thesis deals with the reliability of methods for the speciation of mercury in environmental and biological samples. Problems with speciation methods that couple chromatography to atomic spectrometric detection and how to overcome the problems are discussed. Analytical techniques primarily studied and evaluated are high performance liquid chromatography-cold vapour-atomic absorption spectrometry (HPLC-CV-AAS), HPLC-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), capillary electrophoresis-ICP-MS (CE-ICP-MS) and gas chromatography-ICP-MS (GC-ICP-MS). Applying a multi-capillary approach increased the analyte amount injected into a CE-ICP-MS system and improved the overall sensitivity. A microconcentric nebulizer with a cyclone spray chamber was shown to improve the detection limits for mercury species 3-13 times in HPLC-ICP-MS and 11-19 times in CE-ICP-MS compared to a cross-flow nebulizer with a Scott spray chamber. To decrease the interference of water vapour in HPLC-CV-AAS a Nafion dryer tube was inserted between the CV-generation and the detector. Methyl mercury was however lost in the Nafion unless it was reduced to elemental mercury prior transport through the dryer tube. During sample pre-treatment, incomplete extraction, losses and transformation (alkylation, dealkylation, oxidation and reduction) of mercury species can lead to significant errors (underestimation and overestimation) in the determination of the concentrations. Methods to detect and determine the degree of transformation as well as correct for errors caused by transformation are presented in the thesis. The preferable method use species-specific enriched stable isotope standards in combination with MS detection and a matrix based calculation scheme. This approach is very powerful as both the concentrations of the species as well as the degrees of transformation can be determined within each individual sample.
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Gestión y estrategias de comunicación corporativa en los sectores tradicionales de la Comunidad Valenciana. Claves para la integración y desarrollo de políticas de comunicación como activo estratégico de la competitividad empresarialBlay Arráez, Rocío 26 March 2010 (has links)
La tesis, tiene su punto de partida en la idea de que la imagen y la comunicación corporativa, correctamente gestionadas, son activos estratégicos al servicio de cualquier organización. Además, considera que alcanzar una imagen corporativa positiva, que con el tiempo y la coherencia en su gestión se convierta en buena reputación, es fundamental para la competitividad empresarial. Es más, defiende que la creación de marcas fuertes, contribuye no sólo al desarrollo de las propias empresas sino que también dota de valor a un territorio. Concretamente los protagonistas de la investigación son los clusters de la agroalimentación, calzado, cerámica, iluminación, juguete, mueble y textil, sectores estratégicos de alto valor socioeconómico para la Com. Valenciana. Se analiza primero cómo gestionan dicho activo, a través de las Asoc. Empresariales, la Dir. General de empresas y también, con la consideración de los profesionales de la comunicación valencianos. Y finaliza, planteando en una fase prospectiva las claves para la integración y desarrollo de políticas de comunicación en estos sectores.
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Nanocluster-rich SiO2 layers produced by ion beam synthesis: electrical and optoelectronic propertiesGebel, Thoralf 31 March 2010 (has links) (PDF)
The aim of this work was to find a correlation between the electrical, optical and microstructural properties of thin SiO2 layers containing group IV nanostructures produced by ion beam synthesis. The investigations were focused on two main topics: The electrical properties of Ge- and Si-rich oxide layers were studied in order to check their suitability for non-volatile memory applications. Secondly, photo- and electroluminescence (PL and EL) results of Ge-, Si/C- and Sn-rich SiO2 layers were compared to electrical properties to get a better understanding of the luminescence mechanism.
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Amperometric biosensor systems prepared on poly(aniline-ferrocenium hexafluorophosphate) composites doped with poly(vinyl sulfonic acid sodium salt).Ndangili, Peter Munyao. January 2008 (has links)
<p>The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media / shuttling electrons between HRP and GCE for biosensor applications.</p>
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Development of amperometric biosensor with cyclopentadienylruthenium (II) thiolato schiff base self-assembled monolayer (SAM) on goldTicha, Lawrence Awa January 2007 (has links)
A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(&eta / 5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication
between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, &Gamma / , of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 &mu / M, 6.92 &mu / M and 7.01 &mu / M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively.
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Development of amperometric biosensor with Cyclopentadienylruthenium(ii) thiolato schiff base selfassembled Monolayer (sam) on goldTicha, Lawrence Awa 11 1900 (has links)
A novel cyclopentadienylruthenium(II) thiolato Schiff base,[Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(η5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, Γ, of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 μM, 6.92 μM and 7.01 μM for hydrogen peroxide, cumene
hydroperoxide and tert-butylhydroperoxide respectively / Magister Scientiae - MSc
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Komenského Labyrint světa a Ráj srdce a jeho biblická inspirace / Comenius' Labyrinth of the World and Paradise of the Heart and biblical inspirationVARADY, Veronika January 2015 (has links)
The thesis aims to investigate the relationship Comenius to Scripture and how to work with him when he wrote his work The Labyrinth of the World and the Paradise of the Heart.
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Development of amperometric biosensor with cyclopentadienylruthenium (II) thiolato schiff base self-assembled monolayer (SAM) on goldTicha, Lawrence Awa January 2007 (has links)
Magister Scientiae - MSc / A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(η5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, Γ, of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 M, 6.92 M and 7.01 M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively. / South Africa
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Možnosti fixace vzorků pro měření obsahu DNA u ryb průtokovou cytometriíHUBÁLEK, Martin January 2018 (has links)
This thesis aims to assess the possibility of the usage of various biological fixatives for fish cell and tissues samples in order to extend its storage for later flow cytometric measurement of DNA content. The model species chosen were sterlet and tench, from which three types of samples were obtained: blood and fin tissue of subadult / adult individuals and tail tissue of hatched larvae. Altogether 13 fixation methods were tested for each type of sample of both model species. Methods were chosen based upon their easy feasibility and low time-consumption. The samples were measured on flow cytometer in native state immediately after sampling and placing in physiological saline and after 1, 5 and 10 days of fixation during which they were stored in a fridge or in a freezer at -80 ?C. Their analysis was carried out simultaneously with standards native cells from tench fin tissue when investigating sterlet samples, and commercially available fixed trout erythrocytes for tench samples. A fluorochrome used was 4',6-diamidine-2'-phenylindole dihydrochloride (DAPI; with excitation/emission maxima 358 / 461 nm). Based on the evaluation of coefficients of variation (CV) of fixed samples and the changes in their fluorescence levels in comparison with native state, optimal procedures for extended storage of all types of samples from both model species are suggested.
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Desenvolvimento de estratégias analíticas visando avaliação nutricional e toxicológica de arrozSilva, Douglas Gonçalves da 12 1900 (has links)
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Tese Doutorado Douglas Gonçalves da Silva.pdf: 2348008 bytes, checksum: 01d5eb52cbdd6aa3d019b03a07db5771 (MD5) / CNPq / Neste trabalho foram desenvolvidas estratégias analíticas visando a determinação
de espécies metálicas em amostras de arroz utilizando procedimento de digestão
ácida em micro-ondas e em bloco digestor para o preparo das amostras. Na primeira
parte deste trabalho desenvolveu-se um sistema automático para determinação de
mercúrio em amostras de arroz empregando injeção em fluxo com multiseringa
(MSFIA) e detecção por fluorescência atômica com vapor frio (CV-AFS).
Inicialmente, empregou-se o planejamento fatorial completo para avaliação
preliminar das variáveis que afetavam o sistema. Em seguida, o planejamento
Doehlert foi utilizado com o objetivo de se obter condições ótimas (SnCl2 3% (m/v)
em HCl 2%; vazão da amostra 3 mL min-1 e HNO3 8% (v/v)). O LD e LQ foram iguais
a 0,48 e 1,61ng g -1, respectivamente. O desvio padrão relativo foi menor que 2%
para uma amostra com concentração de mercúrio igual a 3,63 ng g-1. As
concentrações de mercúrio encontradas nas amostras de arroz variaram na faixa de
2,15 a 7,25 ng g-1. Na segunda parte deste trabalho foi proposto um procedimento
simples, eficiente e reprodutível para a determinação de cádmio em amostras de
arroz por espectrometria de absorção atômica com forno de grafite empregando
modificação química permanente com 400 μg de alumínio. Os experimentos foram
realizados utilizando-se tubo de grafite com plataforma integrada e aquecimento
transversal. Para avaliação da modificação permanente, foram realizados
experimentos na ausência e na presença de modificação química convencional com
paládio e fosfato de amônio. O programa de temperatura do forno de grafite para a
determinação de cádmio foi otimizado para cada tipo de modificador permanente a
fim de avaliar a sensibilidade por meio das curvas de pirólise e atomização. A
temperatura ótima de pirólise e atomização obtidas foram de 400 e 1800 ºC uma vez
que nestas temperaturas os níveis de fundo apresentaram-se baixo, não sendo
observada perda de sensibilidade. A massa característica (mo) e o LD do método
foram 1,32 pg e 1,8 ng g-1, respectivamente, e a vida útil do tubo de grafite foi de
1080 queimas. O desvio padrão relativo foi igual a 1,67 %, demonstrando uma boa
precisão do método. As características analíticas foram comparadas com os
métodos recomendados na literatura. No terceiro trabalho avaliou-se a composição
mineral de Ca, K, Mg, Na, Zn, Fe, Mn, Sr e Zn em arroz integral, parboilizado e
amostras de arroz branco usando ICP OES. O efeito do cozimento no conteúdo
mineral também foi investigado. Todos os dados obtidos foram avaliados utilizando
as técnicas de análise multivariada PCA e HCA. O procedimento avaliado
apresentou uma boa exatidão, evidenciada pela análise de material certificado.
Foram alcançados baixos limites de detecção e quantificação e coeficientes de
correlação maiores que 0,999. / In this work, strategies analytical were developed aiming determination of metallic
species in rice samples using acid digestion procedure in microwave and block
digestor for preparation of the samples. In the first part of this work we developed an
automated system for determination of mercury in rice samples using flow injection
with multiseringa (MSFIA) and detection by cold vapor atomic fluorescence (CVAFS).
Initially, we used a full factorial design for preliminary evaluation of the
variables affecting the system. Then, the planning Doehlert was used in order to
obtain optimal conditions (SnCl2 3% (w / v) in 2% HCl, sample flow 3 mL min-1 and
HNO3 8% (v / v)). The LD and LQ were equal to 0.48 and 1.61 ng g -1, respectively.
The relative standard deviation was less than 2% for a sample with a mercury
concentration of 3.63 ng g-1. The mercury concentrations found in samples of rice in
a range from 2.15 to 7.25 ng g-1. In the second part of this work we propose a simple,
efficient and reproducible for the determination of cadmium in rice samples by atomic
absorption spectrometry with graphite furnace employing permanent chemical
modification with 400 mg of aluminum. The experiments were performed using
graphite tube with integrated platform and cross warming. For evaluation of
permanent modification, experiments were performed in the absence and presence
of conventional chemical modification with palladium and ammonium phosphate. The
temperature program graphite furnace for the determination of cadmium was
optimized for each type of permanent modifier to assess the sensitivity curves by
means of pyrolysis and atomization. The optimum temperature pyrolysis and
atomization obtained were 400 and 1800 °C temperatu res since these background
levels are presented below, with no observed loss of sensitivity. The characteristic
mass (mo) and LD method were 1.32 pg and 1.8 ng g-1 respectively and lifetime of
the graphite tube was 1080 firings. The relative standard deviation was equal to
1.67%, showing a good accuracy of the method. The analytical characteristics were
compared with the methods recommended in the literature. In the third study
evaluated the mineral composition of Ca, K, Mg, Na, Zn, Fe, Mn, Sr and Zn in brown
rice, parboiled and white rice samples using ICP OES. The effect of cooking on the
mineral content was also investigated. All data were evaluated using multivariate
analysis PCA and HCA. The procedure evaluated showed good accuracy, as
evidenced by the analysis of certified material. Were achieved low limits of detection
and quantification and correlation coefficients greater than 0.999.
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