UV spectrometry (187–380 nm) with charge coupled device (CCD) detection was used to study the evolution of absorption spectra during the vaporization of various species in the pyrocoated graphite furnace, with electrodeposited Ir and Rh as modifiers. In order to mimic a typical matrix composition, various salts of aluminum, manganese, copper, magnesium, sodium, and lead were used in microgram amounts. Changes in spectra and vapor release rate, along with aging of the tubes in the repetitive temperature cycles, were observed. Compared to the unmodified pyrocoated tubes, the presence of Ir or Rh causes a significant reduction in the vaporization efficiency, especially for microgram amounts of copper and aluminum introduced as nitrates, and manganese introduced as a sulfate. The vaporization efficiency, for magnesium and sodium as chlorides, and for lead as a sulfate, remained unchanged. Interestingly, the aging of the tubes was accompanied by partial restoration of the spectral characteristics for unmodified tubes. For example, with unmodified pyrocoated tubes, the vaporization spectrum, appearing as a consequence of the decomposition of aluminum nitrate, consisted of Al2O bands overlapped by Al atomic lines. In the freshly modified tubes, intensities of those lines and bands were substantially reduced, and in this case, the dominance of AlO molecules was observed. The efficiency of vaporization of aluminum species increased in the aged modified tubes. The scanning electron microscopy (SEM) images of the modified surfaces for the new and aged tubes indicated that aging of the tubes is accompanied by the destruction of the pyrocoating, formation of pyrographite shells around the areas where the modifier was electrodeposited, and finally, complete substitution of the metal on the graphite surface by pyrographite debris.

No description available.

Two perceived limitations of conventional atomic spectrometry were addressed in these studies. One limitation is that the time required for sample preparation can exceed the actual analysis time by two or more orders of magnitude. High pressure homogenization in combination with high speed blending was evaluated for the preparation of slurries which could be directly analyzed by graphite furnace atomic absorption spectrometry (GF-AAS). Cadmium, copper and lead concentrations were successfully determined in certified reference materials (CRMs) of biological origin and frozen cervine liver and kidney. By capping the flat valve head of the homogenizer with a ruby disc, metal contamination introduced by the processing was reduced appreciably (but not eliminated) and the procedure was extended to the determination of chromium, iron, manganese and nickel in botanical CRMs and air dried animal feeds. The one problematic analyte element proved to be selenium which was consistently underestimated with this procedure. However, the combination of high pressure homogenization and partial enzymatic digestion with a crude protease alone or admixed with lipase or cellulase, released Se-residues from zoological and botanical CRMs so that Se could be accurately determined by slurry introduction GF-AAS. This technique was also applied successfully to freeze-dried, fresh and boiled fish tissues. The principal advantages of the slurry preparation technique are its speed, simplicity and lack of operator intervention. / The second limitation involved the loss of chemical speciation information during analysis. To preserve this speciation information, individual chemical species were separated chromatographically then detected in the column eluate using a novel all silica T-tube interface coupled with AAS. The advantages of the current interface design over previous prototypes were the compatibility with both organic or aqueous mobile phases and the low limits of detection (LODs) for Ag, Cd, Cu or Zn. The feasibility of the approach was demonstrated by monitoring levels of metal analyte bound to individual metallothionein isoforms which had been partially resolved by size exclusion or ion exchange HPLC. Whereas the metallothionein-I (MT-I) isoform was enriched in Cu relative to the MT-II isoform, the reverse was true for Zn. Also, a Ag-saturation procedure rapidly and efficiently replaced the bound Cd, Cu and Zn in these polypeptides.

Elemental speciation has been one of the principal growth areas in analytical atomic spectrometry. This reflects the recognition that in the environmental and biological sciences, the transport, pool dynamics and toxicology of the elements are dependent on their chemical speciation. Significant progress has been made in elemental speciation by the direct coupling of separation techniques, notably the various forms of chromatography, to powerful elemental detectors such as ICP-MS. However, the strength of such hyphenated techniques, that they provide almost unambiguous identification of elemental associations, is often achieved at the expense of losing information about the ligands that are responsible for the speciation. The challenge must be to bring the two approaches to bear simultaneously so that quantitative and qualitative information on both the inorganic and organic components can be obtained simultaneously. Capillary electrophoresis (CE) has developed into one of the most powerful separation techniques offering rapid separations with high resolution. However, these advantages are offset by low sensitivity which is a consequence of the very small (nl) samples that the technique can handle. These problems can be overcome by using high sensitivity detectors and hence the interest in coupling CE to .ICP-MS. Coupling of CE to ICP-MS (CE-ICP-MS) has, therefore, the potential to provide rapid and quantitative elemental speciation information that is complementary to that provided by other techniques. This thesis describes an interface for coupling CE to ICP-MS and its applications to some common metal species. A particular interest in this work has been to investigate the potential of CE for studying metal complexes with humic and fulvic acids. A technique that offers potential for determining both free element and complexed forms, without prior separation IS electrospray/ion spray ionisation-mass spectrometry. Preliminary work is presented that investigates the applications of electrospray/ion spray ionisation-mass spectrometry to some common metal-ligand systems.

The field of analytical chemistry is very important to today's society as more and more regulations and legislations emerge regarding trace elements in food, consumer products, medicines, and the environment. Like many areas of science, the current goals of trace elemental measurements and speciation are to increase knowledge on the subject and to improve upon current techniques by enhancing the figures of merit, such as accuracy and reproducibility, meanwhile balancing with the cost and time of analysis. The topics covered in this work were investigated primarily through the use of inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The phenomenon of compound-dependent responses in plasma spectrometry is discussed, seeking possible causes of it and offering some advice on how to prevent it. A new method was developed for the speciation of selenium in dietary supplements using anion-exchange chromatography ICP-MS. A novel method for the determination of total mercury at trace concentrations in rice was developed for use with conventional ICP-MS. Inductively coupled plasma mass spectrometry was also used for fingerprinting the rare earth elements in Maya archaeological pottery for provenance studies.

Orientador: Gustavo Rocha de Castro / Banca: Maria del Pilar Taboada Sotomayor / Banca: Pedro de Magalhaes Padilha / Banca: Rafael Arromba de Sousa / Banca: José Augusto da Col / Resumo: A demanda por novos sistemas de nebulização e/ou introdução de amostras mais flexíveis e, preferencialmente, de baixo fluxo com aproveitamento total da solução em espectrometria atômica surge em decorrência da necessidade de desenvolvimento de novas interfaces para a hifenação com técnicas cromatográficas, a qual está sendo empregada em estudos de especiação química em que se tem pouca disponibilidade de amostras e necessidade de incremento da sensibilidade. Além disso, existe a possibilidade de criação de novas configurações de instrumentos portáteis, redução de custos e menor geração de descartes e efluentes. Neste contexto, foram estudados dois novos sistemas de introdução de amostras: nebulização eletrônica por malha oscilante e a geração fotoquímica de vapores. Nebulizadores de malha oscilante são dispositivos eletrônicos de geração de aerossol desenvolvidos para administração de fármacos específicos para doentes de fibrose cística dos pulmões. Trata-se de um dispositivo portátil, silencioso, sem a necessidade de gás para a geração do aerossol, produzindo um aerossol formado por gotículas de distribuição uniforme (monomodal) com tamanho de partículas de 3 µm. Não há relatos na literatura que, empregando estes sistemas em espectrometria atômica, haveria um grande potencial de abertura de um novo campo de estudos. Verificou-se que nebulizadores eletrônicos permitem que sejam promovidas determinações multielementares empregando apenas 100µL de solução da amostra com grande ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The need for new systems for nebulization and / or introduction of more flexible and preferably low flow samples with full use of the solution in atomic spectrometry arises through the need to develop new interfaces for the hyphenation with chromatographic techniques, which is being used in studies of chemical speciation in which there is little availability of samples and need for increased sensitivity. In addition, there is the possibility of creating new configurations of portable instruments, reducing costs and less generation of discards and effluents. In this context, two new systems of sample introduction were studied: electronic nebulization by vibrating mesh membrane and the photochemical generation of vapors. Vibrating mesh membrane nebulizers are electronic aerosol generation devices developed for administration of specific drugs to cystic fibrosis patients of the lungs. It is a portable, quiet device without the need for gas to generate the aerosol, producing an aerosol formed by uniformly distributed (monomodal) droplets with a particle size of 3 μm. There are no reports in the literature that, employing these systems in atomic spectrometry, there would be great potential for opening up a new field of study. It was verified that electronic nebulizers allow multielement determinations to be promoted employing only 100μL of sample solution with great increase of sensitivity, being able to vary between 10 until 200 times, depending on the element and wavelength. The... (Complete abstract click electronic access below) / Doutor

The soil, as a part of ecosystem, is permanently endangered by pollution and exposed to degradation. A large share on this pollution has a human. This problem is caused mainly by industrial production, agriculture and transport. Intensive chemical maintenance is necessary during winter. It is because of better driving on the roads. Chemicals gradually soak into the soil and contaminate it. This master thesis deals with the analysis of soil samples from close proximity of road from Veseli nad Luznici to Trebon. There was analyzed the concentration of copper, sodium and zinc. Samples were collected in two depths: from 0 to 15 cm (surface sample) and 15 to 30 cm (subsurface sample). The mentioned metals were analyzed by atomic spectrometry. The measured value concentration of copper was between 2.24 mg-kg-1 and 84.35 mg-kg-1, the sodium concentration was from 11 mg-kg-1 to 1 697 mg-kg-1 and the zinc concentration was in the range of 9 mg-kg-1 526 mg-kg-1. The highest concentration of copper (84.35 mg-kg-1) was found in the subsurface sample taken from the immediate proximity of the railway in February 2017. The highest concentration of sodium (1 697 mg-kg-1) was measured near the road in February 2016. The highest concentration of zinc (526 mg-kg-1) was measured near railway in October 2015.

O Estudo de Dieta Total (EDT) tem sido recomendado pela Organização Mundial da Saúde como o método mais adequado para estimar as ingestões dietéticas de contaminantes e nutrientes para um país ou grandes grupos populacionais. O presente estudo é o segundo realizado no Brasil, atualizado com dados da Pesquisa de Orçamento Familiar-POF 2008-2009 do IBGE, para avaliação de ingestão dietética dos elementos essenciais e tóxicos referente à região Sudeste do Brasil. Os alimentos que compõe a lista de alimentos foram coletados em mercados, preparados como prontos para consumo, liofilizados e homogeneizados para a análise pelos Métodos de Análise por Ativação com Nêutrons Instrumental (INAA) e Absorção Atômica com Forno de Grafite (GF-AAS). Foram determinados os elementos As, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Na, Rb, Sc, Se e Zn. Os valores de ingestão dietética diária dos elementos foram calculados e mostraram-se satisfatórios para os elementos Cl, Cu, Fe, Mg, Mn, Se e Zn. Para Ca, Cr e K as ingestões dietéticas calculadas encontraram-se abaixo das recomendações nutricionais. Já para os elementos cujos valores de ingestão diária média superaram as recomendações nutricionais (Cu, Fe, Mg e Mn), as ingestões foram comparadas com os valores de Limite tolerável de ingestão (UL). Concluiu-se que nenhum elemento se encontrava em quantidade acima desses limites, exceto o Na que apresentou valor ligeiramente mais alto que o UL. Em relação aos elementos tóxicos, os valores de concentração estiveram muito abaixo dos valores limites estabelecidos pela legislação brasileira, exceto para o As no grupo de peixes. Porém a ingestão de peixe é baixa, o que contribuiu para que a ingestão dietética de As nesse estudo estivesse bem abaixo do limite máximo tolerável preconizado pela JECFA (Joint FAO/WHO Expert Committee on Food Additives), assim como o valor de ingestão dietética mensal de Cd, que esteve bem abaixo limite tolerável mensal (PTMI). / The World Health Organization (WHO) has been encouraging Total Diet Study (TDS) since WHO considered this study to be the most adequate method to estimate the dietary intakes of contaminants and nutrients of countries or populations on a large-scale. This study is the second carried out in Brazil, and is up to date with data from IBGE National Household Food Budget Survey POF 2008-2009, to evaluate essential and toxic element dietary intakes, concerning the Southeast Region of Brazil. The food represented in food list were collected in supermarkets, preparing read-to-consumed food, freeze-dried and homogenized for analyses, by Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectroscopy (GFAAS). The elements As, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Na, Rb, Sc, Se e Zn were determined. The daily intake values were calculated and the values were satisfactory for the elements Cl, Cu, Fe, Mg, Mn, Se and Zn. For Ca, Cr and K the dietary daily intake values were below the nutritional recommendation. For Cu, Fe, Na, Mg and Mn elements which average daily intakes exceeded the nutritional recommendation, it was observed that no values were above than tolerable upper limits (UL), except for Na which values was slightly higher value than the UL. In relation of toxic elements, the concentration values were below than Brazilian legislation values, except for As in fish group. However the dietary intake of As is below than tolerable upper limit (UL) recommended by JECFA (Joint FAO/WHO Expert Committee on Food Additives) since the fish intake is low in the São Paulo diet. For Cd the month dietary intake was below than PTMI (provisional tolerable monthly intake) recommendation.

O Estudo de Dieta Total (EDT) tem sido recomendado pela Organização Mundial da Saúde como o método mais adequado para estimar as ingestões dietéticas de contaminantes e nutrientes para um país ou grandes grupos populacionais. O presente estudo é o segundo realizado no Brasil, atualizado com dados da Pesquisa de Orçamento Familiar-POF 2008-2009 do IBGE, para avaliação de ingestão dietética dos elementos essenciais e tóxicos referente à região Sudeste do Brasil. Os alimentos que compõe a lista de alimentos foram coletados em mercados, preparados como prontos para consumo, liofilizados e homogeneizados para a análise pelos Métodos de Análise por Ativação com Nêutrons Instrumental (INAA) e Absorção Atômica com Forno de Grafite (GF-AAS). Foram determinados os elementos As, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Na, Rb, Sc, Se e Zn. Os valores de ingestão dietética diária dos elementos foram calculados e mostraram-se satisfatórios para os elementos Cl, Cu, Fe, Mg, Mn, Se e Zn. Para Ca, Cr e K as ingestões dietéticas calculadas encontraram-se abaixo das recomendações nutricionais. Já para os elementos cujos valores de ingestão diária média superaram as recomendações nutricionais (Cu, Fe, Mg e Mn), as ingestões foram comparadas com os valores de Limite tolerável de ingestão (UL). Concluiu-se que nenhum elemento se encontrava em quantidade acima desses limites, exceto o Na que apresentou valor ligeiramente mais alto que o UL. Em relação aos elementos tóxicos, os valores de concentração estiveram muito abaixo dos valores limites estabelecidos pela legislação brasileira, exceto para o As no grupo de peixes. Porém a ingestão de peixe é baixa, o que contribuiu para que a ingestão dietética de As nesse estudo estivesse bem abaixo do limite máximo tolerável preconizado pela JECFA (Joint FAO/WHO Expert Committee on Food Additives), assim como o valor de ingestão dietética mensal de Cd, que esteve bem abaixo limite tolerável mensal (PTMI). / The World Health Organization (WHO) has been encouraging Total Diet Study (TDS) since WHO considered this study to be the most adequate method to estimate the dietary intakes of contaminants and nutrients of countries or populations on a large-scale. This study is the second carried out in Brazil, and is up to date with data from IBGE National Household Food Budget Survey POF 2008-2009, to evaluate essential and toxic element dietary intakes, concerning the Southeast Region of Brazil. The food represented in food list were collected in supermarkets, preparing read-to-consumed food, freeze-dried and homogenized for analyses, by Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectroscopy (GFAAS). The elements As, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Na, Rb, Sc, Se e Zn were determined. The daily intake values were calculated and the values were satisfactory for the elements Cl, Cu, Fe, Mg, Mn, Se and Zn. For Ca, Cr and K the dietary daily intake values were below the nutritional recommendation. For Cu, Fe, Na, Mg and Mn elements which average daily intakes exceeded the nutritional recommendation, it was observed that no values were above than tolerable upper limits (UL), except for Na which values was slightly higher value than the UL. In relation of toxic elements, the concentration values were below than Brazilian legislation values, except for As in fish group. However the dietary intake of As is below than tolerable upper limit (UL) recommended by JECFA (Joint FAO/WHO Expert Committee on Food Additives) since the fish intake is low in the São Paulo diet. For Cd the month dietary intake was below than PTMI (provisional tolerable monthly intake) recommendation.

Propõe-se, pela primeira vez, a associação do tratamento fotocatalítico de amostra, direcionado à degradação e/ou eliminação de interferentes orgânicos, com a separação analito/matriz via geração de hidretos voláteis seguida de determinação por espectrometria de absorção atômica (HG-AAS). O fotocatalisador TiO2 (P-25) foi utilizado sempre em suspensão na amostra, e como fonte de radiação UV empregou-se lâmpada de mercúrio. Duas geometrias de reator fotocatalítico foram examinadas: irradiação estacionária de amostras contidas em cubetas de quartzo (3,5 mL); e irradiação em reator tubular constituído de bobina de Teflon montada em torno da lâmpada. Para avaliar a eficiência do tratamento sob diferentes condições, utilizou-se inicialmente o sistema-modelo Cd(II)-EDTA, com detecção do Cd(II) não quelado por voltametria de pulso diferencial em eletrodo de gota pendente de mercúrio, sabidamente não influenciada pelo TiO2 em suspensão. Nos estudos com HG-AAS, focalizou-se a aplicação do tratamento fotocatalítico à decomposição da arsenobetaína (Asb), um composto modelo interessante por ser refratário aos tratamentos convencionais (micro-ondas + digestão ácida). As condições selecionadas para a etapa de HG-AAS foram: concentração de HCl, 3 mol.L-1, concentração de NaBH4, 1% m/v em NaOH 0,1 mol.L-1, volume de amostra, 0,10 mL e temperatura do atomizador de tubo de quartzo, 980 °C. Nessas condições, as curvas de calibração obtidas por HG-AAS para As(III) e As(V) na faixa de 0,020 a 0,100 mg.L-1 (20 a 100 ppb) apresentaram linearidade e sensibilidade próximas, indicando eficiência de formação similares, característica esta favorável à quantificação total de arsênio em aplicações futuras a amostra reais. Estudos preliminares mostraram que a taxa de recuperação do arsênio é maior no tratamento fotocatalítico realizado em meio alcalino, (pH=12) em razão da menor tendência à adsorção de arsênio em TiO2 nesse meio frente ao neutro e ácido. Parâmetros como o tempo de irradiação, concentração do fotocatalisador e de Asb, além da influência de O2 molecular como scavenger de elétrons também foram investigados. Nas condições selecionadas, partindo-se de uma solução de Asb 0,075 mg.L-1 em arsênio, alcançou-se recuperação aproximada de 80% mediante irradiação por 15 minutos e de 100% após 45 minutos. A decomposição da Asb pelo método fotocatalítico proposto foi confirmada por espectrometria de massa com ionização por electrospray e estudos adicionais poderão revelar se as espécies de arsênio envolvidas na geração da arsina encontram-se completamente mineralizadas. / The combination of photocatalytic sample preparation, aiming degradation of organic interferences, with analyte/matrix separation by generation of volatile hydrides followed by atomic absorption spectrometric determination (HG-AAS) is proposed for the first time in this work, mainly devoted to the investigation of total arsenic analysis. A mercury lamp served as source of UV-radiation and the photocatalyst, TiO2 (P25), was used as a suspension in the sample solution. Two geometries of photocatalytic reactor were examined: stationary irradiation of a set of samples contained in 3.5 mL quartz cuvettes (preferred one for the present application) and stopped-flow irradiation of a sample in a tubular reactor consisting of a Teflon tube coiled around the lamp. Evaluation of the digestion efficiency of the reactors under different conditions was made with help of the model system Cd(II)-EDTA, with detection of the unchelated Cd(II) by differential pulse voltammetry with the hanging mercury drop electrode, known to work in the presence of TiO2 suspension. The subsequent studies in combination with HG-AAS focused on the photocatalytic degradation of arsenobetaine (Asb), chosen as a model because it is particularly resistant to conventional treatments (microwave + acid digestion). The following conditions were established for the HG-AAS step: HCl concentration (3 mol.L-1) and NaBH4 concentration (1% m/v in NaOH 0,1 mol.L-1), sample volume (0.10 mL) and atomization temperature (980 °C). Calibration curves for As (III) and As (V) by HG-AAS in the range of 0,020 to 0,100 mg.L-1 (20 a 100 ppb) conveyed in slope and linearity, indicating the same efficiency of arsine formation from both species, favoring the total quantification of arsenic in the sample. Alkaline medium (pH=12) was preferred for the photocatalytic digestion because recoveries of arsenic were better than in neutral or acidic medium, possibly due to lower losses by adsorption of arsenic species on TiO2. The effects of parameters such as irradiation time, concentration of the photocatalyst and of arsenobetaine, as well as the influence of molecular O2 as an electron scavenger were investigated. Under selected conditions and for a starting solution of 0,075 mg.L-1 Asb an arsenic recovery of 80% approximately was obtained after 15 minutes of irradiation while full recovery required 45 minutes. The decomposition of the Asb molecule after irradiation was confirmed by electrospray mass spectrometry and a further study may reveal if the arsenic species involved in the arsine generation are fully mineralized ones.