The electrodeless plasma discharge is typically driven by radio frequency (RF) power supply within the range (0.2 &iexcl / 40 MHz). The applied power is coupled into the plasma inductively called inductively coupled plasma (ICP). RF ICP technique has achieved significance importance in a diversity of research and industrial applications for over the last threes decades. It is still required to undertake both theoretical and experimental research. In this work, RF ICP technique is applied on the torch modeling in 2D. Based on extended electromagnetic vector potential representation, an axisymmetric model in 2D is proposed for the calculations of the electromagnetic fields in an RF ICP torch. The influence of axial vector potential is included to the vector potential formulations. This is achieved by imposing a helical current carrying wire configuration. The corresponding governing equations are solved numerically by applying finite element method (FEM) using commercial partial differential equation solver (Flex PDE3). Based on this model, the plasma behavior and properties are examined in terms of plasma parameters. Besides, a comparative iii analysis is made between proposed model called helical configuration and the one currently available in the literature called circular configuration. This study shows relatively little difference between temperature fields predicted by two models. However, significant difference is observed between corresponding flows and electromagnetic fields. Especially, tangential flow which is observed in helical configuration vanishes in circular configuration. The proposed model offers an effective means of accounting for the variations of the helical coil geometry on the flow and temperature fields and achieving a better representation of the electromagnetic fields in the discharge. Finally, it is concluded that minimum number of turns (n = 2) yields significant difference between two models whereas, maximum allowable number of turns yield no distinctions on the results of two models in terms of azimuthally applied current. However, axial effect of current still exists but very small with respect to the result obtained with minimum number of turns.

In analytical chemistry the main goal is normally to determine the identity and/or concentration of one or more species in a sample. The samples analyzed are often natural samples, containing numerous different species in a complex matrix and the choice of technique for multi-elemental detection is in general inductively coupled plasma spectrometry. The chemical forms of an element can affect many of its characteristics e.g. toxicity, which makes speciation analysis important. Therefore, determination of the identity and quantity of an element is still important, but for many applications measurements of total element concentration provides insufficient information. To be able to perform speciation analysis, separation, identification and/or characterization of the various forms of elements in the sample has to be accomplished. Speciation analysis has been employed in a wide range of disciplines, including for example environmental science, biology and clinical chemistry. This thesis describes work to improve and understand the elemental speciation analysis with liquid chromatography coupled to plasma spectrometry and also highlights the importance and potential of the synergy between atomic spectrometry and molecular mass spectrometry. The combination of the matrix tolerant, robust and very sensitive plasma spectrometry used together with molecular mass spectrometry, which provides structural information and the possibility to identify unknown species, is demonstrated to be a very powerful tool for speciation analysis. In this thesis methods are developed for on-line sample clean-up and pre-concentration coupled to liquid chromatography and plasma spectrometry, which makes handling of small sample volumes easier and also decreases the risk of contamination. The problems associated with organic modifiers in plasma spectrometry are also addressed. Applications of speciation analysis are exemplified by analysis of aluminium-chelated siderophores in field-soil solutions and organic phosphorous species in aquatic sediments. The possibility to analyze un-dissolved samples as slurries with minimal sample preparation is also discussed.

No description available.

O objetivo deste estudo foi avaliar parâmetros tais como, moagem, tamanho de partículas, homogeneidade, segregação, dissolução de amostras e amostragem de suspensão, visando o desenvolvimento de método para a determinação de Ir, Pd, Pt e Rh por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) em sílica mesoporosa para uso catalítico. Após a moagem em moinho eletrônico de almofariz e pistilo, a análise do tamanho e distribuição das partículas revelou que 89% das partículas apresentam tamanhos <100 &#181;m e 23% com tamanho <5 &#181;m. Na avaliação de segregação dos analitos na amostra, os resultados obtidos para amostra com moagem grosseira, indicaram que os elementos estão distribuídos de maneira heterogênea entre as frações. Entretanto, a moagem fina aumentou a homogeneidade e esta pode ser uma etapa importante e necessária no sentido de evitar segregação da amostra. A análise por difração e de Raios-X mostrou que não ocorreram reações mecanoquímicas durante a moagem e por fluorescência de Raios-X forneceu resultados discrepantes entre os laboratórios, o pode estar relacionado com a heterogeneidade que induziu erros de amostragem. A avaliação de desempenho do ICP OES foi feita a partir do estabelecimento de parâmetros de mérito como seletividade, repetibilidade, estabilidade, robutez e limite de detecção. Na otimização foram considerados os parâmetros potência, vazão de nebulização e vazão de gás auxiliar. Foi feito um estudo em solução aquosa e em meio da amostra para escolha das linhas de emissão dos elementos Ir, Pd, Pt, Rh e dos candidatos a padrões internos. Apesar dos bons resultados encontrados em solução aquosa, o aumento do sinal de fundo em meio da amostra restringiu a escolha dos comprimentos de onda. Para o estudo da dissolução das amostras foram avaliados quatro procedimentos em forno de micro-ondas com frasco fechado. Os melhores resultados foram obtidos com 150 mg de amostra, 6 mL de água régia e 210 ºC de aquecimento durante 60 min. As determinações por ICP OES usando padrões internos Ru para Pd, Yb para Pt e Dy para Rh foram aquelas que forneceram os resultados mais coerentes com aqueles obtidos por fluorescência de Raios-X. Nos estudos visando à introdução de amostra na forma de suspensão foram avaliados: a massa de amostra para o preparo da suspensão, o efeito da concentração de ácido nítrico e o uso de padrão interno na tentativa de corrigir erros de matriz. 60 mg de amostra com um volume final de 20 mL de ácido nítrico 0,5% (v v-1) foram os escolhidos. Entretanto, a determinação dos elementos via suspensão mostrou resultados muito inferiores aos valores de concentrações esperados. Irídio foi investigado somente para otimização de ICP OES porque a sílica mesoporosa para uso de catalisador automotivo tem não esse elemento em sua composição. / The aim of this study was to evaluate parameters such as grinding, particle size, homogeneity, segregation, sample dissolution and slurry sampling for method development for the determination of Ir, Pd, Pt and Rh in silica mesoporosa for catalyst using inductively coupled plasma optical emission spectrometry (ICP OES). After the grind in an electronic grider with mill and pistil, the analysis of the particle size distribution showed 89% of particles with sizes <100 &#181;m and 23% of particles with sizes <5&#181;m. The separation in different particle size fractions showed that the sample with coarse grind (as sent to the lab) is not homogenous for the elements in comparison with that submitted to grind. X-Ray Diffraction and X-Ray Fluorescence analysis did not showed chemical reactions during the grinding, however a discrepancy between results of different laboratories. The performance of ICP OES was made by using figures of merit such as selectivity, repeatability, stability, robustness and limit of detection. In the optimization of ICP OES power supply, nebulizer flow rate and auxiliary gas flow rate were considered. Studies were conducted in aqueous and in the sample solution to choose emission wavelengths for Ir, Pd, Pt, Rh and internal standard candidates. Despite the good results obtained in aqueous solution, increasing the background signal in sample media restricted the choice of the emission wavelengths. For sample dissolution four procedures using microwave oven with closed-vessel were evaluated. The best results were obtained with 150 mg of the sample, 6 mL of aqua-regia and 210 ºC of heating, during 60 min. Determinations by ICP OES using internal standards Ru for Pd, Yb for Pt, and Dy for Rh were those who provided more consistent results in comparison with those obtained by x-ray fluorescence. For slurry sampling introduction sush parameters were evaluated: the mass of sample to prepare the slurry, the effect of the nitric acid concentration and the use of internal standard to correct matrix effects. 60 mg of the sample with a final volume of 20 mL of nitric acid 0.5% (v v-1) were chosen. However, the determination of Pd, Pt and Rh via suspension showed concentrations below to those expected, as determined by ICP OES in solution. Iridium was investigated only for ICP OES optimization because the silica mesoporosa for automobile catalyst use have not this element in its composition.

Orientadores: Felix Guillermo Reyes Reyes, Maria Teresa de Alvarenga Freire / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-16T23:01:27Z (GMT). No. of bitstreams: 1 Dutra_CamilaBraga_D.pdf: 1974104 bytes, checksum: 7a0aae96f3654e27fb7d553ee756e522 (MD5) Previous issue date: 2010 / Doutorado / Doutor em Ciência de Alimentos

The elemental analysis of soil is useful in forensic and environmental sciences. Methods were developed and optimized for two laser-based multi-element analysis techniques: laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS). This work represents the first use of a 266 nm laser for forensic soil analysis by LIBS. Sample preparation methods were developed and optimized for a variety of sample types, including pellets for large bulk soil specimens (470 mg) and sediment-laden filters (47 mg), and tape-mounting for small transfer evidence specimens (10 mg). Analytical performance for sediment filter pellets and tape-mounted soils was similar to that achieved with bulk pellets. An inter-laboratory comparison exercise was designed to evaluate the performance of the LA-ICP-MS and LIBS methods, as well as for micro X-ray fluorescence (μXRF), across multiple laboratories. Limits of detection (LODs) were 0.01-23 ppm for LA-ICP-MS, 0.25-574 ppm for LIBS, 16-4400 ppm for µXRF, and well below the levels normally seen in soils. Good intra-laboratory precision (≤ 6 % relative standard deviation (RSD) for LA-ICP-MS; ≤ 8 % for µXRF; ≤ 17 % for LIBS) and inter-laboratory precision (≤ 19 % for LA-ICP-MS; ≤ 25 % for µXRF) were achieved for most elements, which is encouraging for a first inter-laboratory exercise. While LIBS generally has higher LODs and RSDs than LA-ICP-MS, both were capable of generating good quality multi-element data sufficient for discrimination purposes. Multivariate methods using principal components analysis (PCA) and linear discriminant analysis (LDA) were developed for discriminations of soils from different sources. Specimens from different sites that were indistinguishable by color alone were discriminated by elemental analysis. Correct classification rates of 94.5 % or better were achieved in a simulated forensic discrimination of three similar sites for both LIBS and LA-ICP-MS. Results for tape-mounted specimens were nearly identical to those achieved with pellets. Methods were tested on soils from USA, Canada and Tanzania. Within-site heterogeneity was site-specific. Elemental differences were greatest for specimens separated by large distances, even within the same lithology. Elemental profiles can be used to discriminate soils from different locations and narrow down locations even when mineralogy is similar.

The performance of commercial Radio Frequency Identification (RFID) tags is primarily limited by present techniques used for tag antenna design. Currently, industry techniques rely on identifying the RFID tag application (books, clothing, etc.) and then building antenna prototypes of different configurations in order to satisfy minimum read range requirements. However, these techniques inherently lack an electromagnetic basis and are unable to provide a low cost solution to the tag antenna design process. RFID tag performance characteristics (read-range, chip-antenna impedance matching, surrounding environment) can be very complex, and a thorough understanding of the RFID tag antenna design may be gained through an electromagnetic approach in order to reduce the tag antenna size and the overall cost of the RFID system. The research presented in this thesis addresses RFID tag antenna design process for passive RFID tags. With the growing number of applications (inventory, supply-chain, pharmaceuticals, etc), the proposed RFID antenna design process demonstrates procedures to design tag antennas for such applications. Electrical/geometrical properties of the antennas designed were investigated with the help of computer electromagnetic simulations in order to achieve optimal tag performance criteria such as read range, chip-impedance matching, antenna efficiency, etc. Experimental results were performed on the proposed antenna designs to compliment computer simulations and analytical modelling.

This diploma thesis is focused on the plasma surface treatment of historical glass from the 18th and 19th centuries by low temperature electrical discharges in solutions of sodium chloride and potassium carbonate and finding the most suitable settings of conditions for the surface cleaning. Stainless steel electrode and a specially designed electrode system with wolfram wire in the quartz glass capillary were used for the generation of discharge using an audio frequency power supply. Each line of samples was made from one piece of historical glass that was cut to smaller pieces. All cleaned samples were photographed before and after the cleaning so the possible changes of the cleaned area could be visually compared. Then the samples were analysed by LA-ICP-MS (line scanning of surface), where was analysed the cleaned area of samples, and values were compared to the analysis of the reference sample that was not cleaned. Examined isotopes of elements were selected on the basis of the supposed composition of glass, corrosion products, and soil at the place of discovery. Analyses were standardized by NIST 610. Acquired values were transferred to oxides. The most important oxides (Na2O, MgO, SiO2, P2O5 a K2O) were chosen for deciding the most effective cleaning settings. It was decided that the most effective setting for cleaning was the one where the biggest difference of values between sample and reference occurred. Four series of these solutions were compiled and one parameter was changed for each of them. Solutions and their conductivity, frequency of the power supply, and time of cleaning were chosen as changing values. Three samples of different times of cleaning were cleaned without interruption. The time of cleaning was split into intervals of 30 seconds of cleaning and 1 minute of non-action for another two samples of this series. In this way we were trying to find out if the following surface analysis will be influenced by the diffusion of the particles into the sample, or not. The frequency of power supply was recorded and its dissipated power was calculated for each measurement. Emission spectra of a series of different solution conductivity were measured before cleaning of samples. Measurement of OES was made with the ignition of discharge so the active species of plasma were shown in spectra. These species are probably participating in the cleaning process of glass. Emission spectra were also measured after cleaning to find out if values of active species were changed or unknown spectral lines appeared. These lines should be from dirt and corrosion products that were cleaned from the surface of the glass. It was found out that the most effective cleaning of sample 1 (series where the conductivity of the NaCl solution was changed) was done in a solution of conductivity 900 S/cm. The most effective cleaning of sample 4 and sample 7 (series where the conductivity of the K2CO3 solution was changed) was done in a solution of conductivity 600 S/cm. The most effective cleaning of sample 6 (series where the frequency was changed) was done at frequency = (15200 ± 30) Hz. The most effective cleaning of sample 5 (series of different cleaning times) lasted seven minutes without time delay. The future research it should be appropriate to try a combination of these most effective cleaning settings on the surface of more samples, so the finding of this thesis will be confirmed.

Dependence of glutathione concentration on the amount of thallium in the plant was studied. Observed plant was maize (Zea mays) which was divided to two parts – root and overground. Two culture procedures were elaborated where seeds and young seedlings were cultivated in a solution of thallium of concentration 0, 1, 3, 5, 8, a 10 µmol/l. Extraction agents used during extraction were phosphate buffer and solution of ascorbic acid. Determination of glutathione was realized by capillary electrophoresis (CE) and high performance liquid chromatography (HPLC). Diode array detector (DAD) was used in both methods. Quantification of the thallium amount in the plant was done by method of inductively coupled plasma-atomic emission spectrometry (ICP-AES).

This work deals with elemental analysis of inorganic materials, that are presented by blast furnace slag and geopolymeric material containing fly-ashes. In the theoretical part there are explained principles of elemental analysis of inorganic materials. Ways of dissolution of samples, optical emission spectroscopy and electron microscopy with energy dispersive x-ray analysis are commented. In experimental part the ICP analysis of oxide standards is described. The standards were used for estimation of EDS-correction factors. Then follow the preparation, proving and use of standards in analysis of blast furnace slag. The work is finished by exact analysis of concentration profiles of elements in interface of phases in geopolymeric material.