Generation and atomization of cadmium volatile compounds was optimized in this work in order to determine trace Cd concentration levels by volatile compound generation (VCG) with subsequent detection by atomic absorption spectrometry (AAS). Three designs of volatile compound generators have been tested including a conventional hydride generator in flow injection analysis (FIA) mode, a batch generator as well as a generator of volatile compounds of transition metals. The generation efficiency of Cd species was quantified as low as 4 % in the conventional hydride generator. Providing that dissolved oxygen was removed from the reaction solutions, the generation efficiency of Cd increased to 12 % in the same experimental arrangement. The highest Cd generation efficiency of 54 % was reached in the generator of volatile compounds of transition metals. In this set up a detection limit of 0.07 ng ml-1 Cd and a sensitivity of 3.2 s ng-1 Cd, respectively, were reached. Moreover, the structure of the volatile Cd species generated was identified as free atoms in all experimental arrangements of the generators investigated. Keywords atomic absorption spectrometry, cadmium, generation of volatile compounds, atomization of volatile compounds

EN The present diploma thesis deals with the electrochemical generation of volatile tellurium compounds in connection with atomic absorption spectrometry with the main goal to increase the response of the tellurium signals and thus expand the existing knowledge about this element. Tellurium is one of the heavier elements that forms less stable volatile compounds. The reason for choosing these elements was the fact that its concentration increases mainly in landfills where it is released into the environment, which can have an ecological impact and an impact on human health. In the first step, two types of electrochemical cells were constructed - a thin-film flow electrochemical cell with and without an ion exchange membrane and an apparatus with a flow injection arrangement. The choice of cell types, cathode and anode material and apparatus design was chosen based on a literature research. Attention was paid to the optimization of reaction conditions for electrochemical generation of volatile tellurium compounds, which significantly affect the efficiency of generation using a heated quartz tube atomizer. The optimized parameters were electrolyte concentration, carrier gas volume flow rate, electrolyte volume flow rate and generation current. In the second step, the effect of the temperature of the...

This thesis is focused on increasing the senstitivity of gold determination by electrochemical volatile species generation using two different types of electrolytic cells in continuous flow setting. Externally heated quartz tube atomizer was used as means of atomization and detection of gold with atomic absorption spectrometer. Generation parameters were optimized for electrolytic cell with an ion exchange (nafion) membrane. After selection of new cathode material (Cu) the carrier gas (Ar) flow rate was optimized, where an additional inlet of carrier gas was found to have possitive effect on increasing the sensitivity of determination of gold and efficiency of volatile specie transport to the atomizer. Experiments with Antifoam B showed possitive effect on generation, thus calibration was carried out for optimized experimetal conditions reaching detection limit of 0,53 mg.dm−3 . The efficiency of volatile specie transfer from liquid to gaseous phase was determined between 60 - 65 % by measuring the residual gold content in liquid waste by F-AAS method. Subsequently the effieciency of electrolytic generation of volatile gold specie with radioactive tracer isotopes and autoradigraphy was determined to 0,6 %. These methods confirmed adsorption of generated species on apparatus surface. Using ICP-MS as...

A determinação direta de arsênio total em águas por espectrometria de absorção atômica com filamentos de tungstênio (150 W) modificados quimicamente com irídio ou ródio, representa uma alternativa para a atomização eletrotérmica de arsênio, que foi avaliada na presente dissertação. A utilização do revestimento com Ir como modificador químico proporcionou um aumento da massa característica de arsênio de 3,5 vezes. As medidas foram feitas com altura de observação selecionada para proporcionar a melhor razão sinal/ruído sem diminuir a sensibilidade do sinal analítico. Avaliaram-se dois programas de aquecimento: com temperatura de secagem constante (com diminuição gradativa da tensão aplicada) e com temperatura de secagem variável (com tensão aplicada de maneira constante). Não houve diferença na sensibilidade entre os dois programas estudados, indicando que a modificação química leva à formação de um precursor atômico com estabilidade térmica elevada. De fato, utilizando-se a modificação química permanente com 1000 müg Ir, e adotando-se programa de aquecimento com temperatura de secagem variável, a temperatura máxima de pirólise foi de aproximadamente 1700 °C ( temperatura de atomização de 2700 °C). Avaliou-se o comportamento eletrotérmico do As na presença dos concomitantes Na, K, Ca e Mg em 0,1% v/v HNO3. Interferências mais severas foram observadas na presença de cálcio acima de 10 \'mü\'g l-1, e acima de 100 \'mü\'g l-1 para os demais concomitantes. As interferências podem estar relacionadas com o elevado gradiente de temperatura entre a superfície do filamento e a fase gasosa do volume de observação, ou mesmo devido à formação de compostos refratários, particularmente para Ca e Mg, na fase condensada, ou seja, na superfície do atomizador. O emprego do método das médias móveis no tratamento dos sinais transientes gerados na atomização do arsênio também foi avaliada. Com o filamento posicionado na altura de observação 2 mm, foram utilizados os fatores 0, 3, 5, 7 e 9, observando-se melhora considerável nos limites de detecção instrumental e do método,utilizando-se média móvel com fator 7. Nestas condições, e depositando-se 20 \'mü\'l de amostra sobre o filamento, o limite de detecção foi de 3,2 \'mü\'g l-1 As e a massa característica de 37,0 pg As. A exatidão foi avaliada analisando-se diferentes amostras de águas provenientes da região do Quadrilátero Ferrífero do Estado de Minas Gerais, por espectrometria de fluorescência atômica com geração de hidretos e por espectrometria de absorção atômica com o filamento de tungstênio modificado com Ir. A comparação dos resultados mostrou que o método proposto pode ser utilizado para o controle de qualidade de águas desta região. Aproximadamente 150 queimas podem ser feitas com um único filamento de tungstênio / The direct determination of arsenic in waters by atomic absorption spectrometry with 150 W tungsten coils, treated with Ir or Rh, was evaluated as a possible alternative for the eletrothermal atomization of As. The use of iridium as a permanent chemical modifier did improve the characteristic mass of arsenic by 3.5 fold. Measurements were made by choosing an appropriate observation height in order to get the best signal to noise ratio. Two heating programs were tested, either by keeping the applied voltage constant or by using an inverted voltage ramp during the drying step. There were no significant differences in the sensitivities between both heating programs, indicating that the permanent modification lead to the formation of an atomic precursor of high thermal stability. Indeed, with the permanent chemical modification with 1000 \'mü\'g Ir, the maximum pyrolysis temperature was approximately 1700 °C (atomization temperature 2700 °C), allowing a heating program with temperature variation during the drying step. Method selectivity was carried out by evaluating the eletrothermal behavior of As in the presence of up to 1000 \'mü\'g l-1 Na, K, Ca and/or Mg in 0,1% v/v HNO3. The most serious interferences were observed with Ca in concentrations higher than 10 \'mü\'g l-1 and when the concentrations were higher than 100 \'mü\'g l-1 for Na, K or Mg, which can be attributed either to the gradient of temperature between the surface of the atomizer and the observation volume or to the formation of refractory compounds in the condensed phase, particularly with Ca and Mg. The absorbance transient signals treatment by the method of moving averages up to factor 9 was also evaluated, with a remarkable improvement in the instrumental and method detection limits. With the center of the observation volume 2 mm above the tungsten coil surface, and a moving average of factor 7, the limit of detection was 3,2 \'müg\' l-1 As and the characteristic mass 37,0 pg As. Accuracy was evaluate by analysing water samples collected in a contaminated area from the Quadrilátero Ferrífero, Minas Gerais State, by hydride generation atomic fluorescence spectrometry and by tungsten coil eletrothermal atomic absorption spectrometry. Results showed that the proposed method fits for the purpose of CONAMA 357 regulation for drinking water quality in the aforementioned contaminated area. Approximately 150 firings can be done with a single tungsten coil atomizer by using 20 \'mü\'l sample volume

Um método de baixo custo é proposto para determinação direta de chumbo em açúcar por espectrometria de absorção atômica com forno de grafite e correção de fundo com fonte de deutério, empregando modificação química permanente com 250µg W + 200µg Rh e co-injeção de 5µg Rh. Os experimentos foram realizados com plataforma integrada ou ao no tubo de grafite com aquecimento longitudinal. Para avaliação da modificação química permanente, foram feitos experimentos na ausência de modificação e na presença de modificação química convencional com Pd+Mg. No decorrer do trabalho observou-se ser imprescindível a co-injeção de Rh para a estabilização térmica de chumbo na presença de açúcar. A amostra (8 g) é dissolvida em 100 ml de solução aquosa 0,2% v/v HNO3, e uma alíquota de 10 l é injetada com 5µl de solução de Rh na plataforma do tubo de grafite modelo Universal da Varian tratada com W e Rh. A massa característica (mo) e o limite de detecção do método foram 11 pg Pb e 5 ng g-1 respectivamente, e a vida útil do tubo de grafite foi de 860 queimas. O método apresentou boa reprodutibilidade com coeficiente de variação inferior a 2,5 % (n=3). As características analíticas foram comparadas com os métodos recomendados na literatura. A exatidão do método proposto para determinação direta de chumbo em açúcar foi avaliada pela comparação com método convencional utilizando Pd+Mg e nenhuma diferença estatística foi observada aplicando-se o teste t de Student ao nível de 95% de probabilidade, em amostras que receberam adição de chumbo / A simple method for the direct determination of lead in sugar by graphite furnace atomic absorption spectrometry (GFAAS) with platform treated with 250µg W + 200µg Rh and deuterium background correction is proposed. Samples (8 g) were dissolved in 100 ml of an aqueous solution containing 0,2% v/v HNO3 and 10µl aliquots were co-injected with 5µg Rh into the integrated platform modified with W-Rh of the Universal Varian longitudinal heated graphite atomizer. The characteristic mass (mo) and the method detection limit were 11 pg Pb and 5,0 ng g-1 Pb, respectively, and the tube life time was 860 firings. The relative standard deviation of measurements (n=3) was lower than 2,5 %. For the evaluation of the permanent chemical modifier, parallel experiments were carried in the presence of diluted nitric acid and with the conventional Pd+Mg chemical modifier. Experiments were made either with manual inserted graphite plataforms or integrated plataforms into longitudinal graphite tubes. Comparison of the proposed method with a method based on Pd+Mg chemical modifier showed no statistical differences by applying a t-test at 95% confidence level, for sugar sample solution spiked with lead

A determinação direta de arsênio total em águas por espectrometria de absorção atômica com filamentos de tungstênio (150 W) modificados quimicamente com irídio ou ródio, representa uma alternativa para a atomização eletrotérmica de arsênio, que foi avaliada na presente dissertação. A utilização do revestimento com Ir como modificador químico proporcionou um aumento da massa característica de arsênio de 3,5 vezes. As medidas foram feitas com altura de observação selecionada para proporcionar a melhor razão sinal/ruído sem diminuir a sensibilidade do sinal analítico. Avaliaram-se dois programas de aquecimento: com temperatura de secagem constante (com diminuição gradativa da tensão aplicada) e com temperatura de secagem variável (com tensão aplicada de maneira constante). Não houve diferença na sensibilidade entre os dois programas estudados, indicando que a modificação química leva à formação de um precursor atômico com estabilidade térmica elevada. De fato, utilizando-se a modificação química permanente com 1000 müg Ir, e adotando-se programa de aquecimento com temperatura de secagem variável, a temperatura máxima de pirólise foi de aproximadamente 1700 °C ( temperatura de atomização de 2700 °C). Avaliou-se o comportamento eletrotérmico do As na presença dos concomitantes Na, K, Ca e Mg em 0,1% v/v HNO3. Interferências mais severas foram observadas na presença de cálcio acima de 10 \'mü\'g l-1, e acima de 100 \'mü\'g l-1 para os demais concomitantes. As interferências podem estar relacionadas com o elevado gradiente de temperatura entre a superfície do filamento e a fase gasosa do volume de observação, ou mesmo devido à formação de compostos refratários, particularmente para Ca e Mg, na fase condensada, ou seja, na superfície do atomizador. O emprego do método das médias móveis no tratamento dos sinais transientes gerados na atomização do arsênio também foi avaliada. Com o filamento posicionado na altura de observação 2 mm, foram utilizados os fatores 0, 3, 5, 7 e 9, observando-se melhora considerável nos limites de detecção instrumental e do método,utilizando-se média móvel com fator 7. Nestas condições, e depositando-se 20 \'mü\'l de amostra sobre o filamento, o limite de detecção foi de 3,2 \'mü\'g l-1 As e a massa característica de 37,0 pg As. A exatidão foi avaliada analisando-se diferentes amostras de águas provenientes da região do Quadrilátero Ferrífero do Estado de Minas Gerais, por espectrometria de fluorescência atômica com geração de hidretos e por espectrometria de absorção atômica com o filamento de tungstênio modificado com Ir. A comparação dos resultados mostrou que o método proposto pode ser utilizado para o controle de qualidade de águas desta região. Aproximadamente 150 queimas podem ser feitas com um único filamento de tungstênio / The direct determination of arsenic in waters by atomic absorption spectrometry with 150 W tungsten coils, treated with Ir or Rh, was evaluated as a possible alternative for the eletrothermal atomization of As. The use of iridium as a permanent chemical modifier did improve the characteristic mass of arsenic by 3.5 fold. Measurements were made by choosing an appropriate observation height in order to get the best signal to noise ratio. Two heating programs were tested, either by keeping the applied voltage constant or by using an inverted voltage ramp during the drying step. There were no significant differences in the sensitivities between both heating programs, indicating that the permanent modification lead to the formation of an atomic precursor of high thermal stability. Indeed, with the permanent chemical modification with 1000 \'mü\'g Ir, the maximum pyrolysis temperature was approximately 1700 °C (atomization temperature 2700 °C), allowing a heating program with temperature variation during the drying step. Method selectivity was carried out by evaluating the eletrothermal behavior of As in the presence of up to 1000 \'mü\'g l-1 Na, K, Ca and/or Mg in 0,1% v/v HNO3. The most serious interferences were observed with Ca in concentrations higher than 10 \'mü\'g l-1 and when the concentrations were higher than 100 \'mü\'g l-1 for Na, K or Mg, which can be attributed either to the gradient of temperature between the surface of the atomizer and the observation volume or to the formation of refractory compounds in the condensed phase, particularly with Ca and Mg. The absorbance transient signals treatment by the method of moving averages up to factor 9 was also evaluated, with a remarkable improvement in the instrumental and method detection limits. With the center of the observation volume 2 mm above the tungsten coil surface, and a moving average of factor 7, the limit of detection was 3,2 \'müg\' l-1 As and the characteristic mass 37,0 pg As. Accuracy was evaluate by analysing water samples collected in a contaminated area from the Quadrilátero Ferrífero, Minas Gerais State, by hydride generation atomic fluorescence spectrometry and by tungsten coil eletrothermal atomic absorption spectrometry. Results showed that the proposed method fits for the purpose of CONAMA 357 regulation for drinking water quality in the aforementioned contaminated area. Approximately 150 firings can be done with a single tungsten coil atomizer by using 20 \'mü\'l sample volume

O consumo do pescado é importante para a saúde humana pelo fato desse alimento ser fonte de proteína de alta qualidade, vitaminas, nutrientes essenciais e dois ácidos poli-insaturados ômega-3. Entretanto, o pescado também pode apresentar risco à saúde humana se estiver contaminado por substâncias tóxicas. Visando avaliar o teor de elementos essenciais e tóxicos, foram utilizado as técnicas de Análise por Ativação Neutrônica e Espectrometria de Absorção Atômica na determinação dos elementos As, Br, Cd, Cl, Co, Cr, Cs, Fe, Hg, K, Mg, Mn, Na, Pb, Rb, Sb, Se e Zn nos tecidos comestíveis (filés) de seis pescados dentre os mais consumidos na cidade de São Paulo: corvina - Micropogonias furnieri (Desmarest, 1823); pescada - Cynoscion leiarchus (Cuvier, 1830); robalo - Centropomus undecimalis (Bloch, 1792); sardinha - Sardinella brasiliensis (Steindachner, 1879); anchova - Pomatomus saltatrix (Linnaeus, 1766) e tainha - Mugil liza (Valenciennes, 1836). Para validar os métodos analíticos utilizados em relação à exatidão, foram utilizados o índice z e o valor de HorRat em materiais de referência certificados analisados sob as mesmas condições das amostras. Os elementos Br, K e Na foram determinados por duas modalidades de irradiação e o teste-t de Student foi utilizado para verificar se havia ou não diferença significativa entre as técnicas. Na determinação dos elementos essenciais e potencialmente tóxicos, foi possível a construção de banco de dados para os elementos Br, Cl, Co, Cs, Fe, K, Mg, Mn, Na, Rb, Se e Zn para potenciais futuras discussões. Para avaliar se havia ou não risco à segurança alimentar, foram comparado os teores de As, Cd, Hg e Pb com a legislação vigente no Brasil e com valores internacionais. Em relação à segurança alimentar, para os contaminantes Cd e Pb foram obtidos teores abaixo de todos os limites técnicos usados neste trabalho. Para As, a maior parte deve estar na forma orgânica, portanto, a determinação de Hg se mostrou determinante. De forma geral, não haveria perigo no consumo da sardinha, pescada, tainha, corvina e robalo, enquanto que para a anchova foi inconclusivo. / Fish consumption is important for human health because this food is a source of high-quality protein, vitamins, essential nutrients and two kinds of omega-3 polyunsaturated acids. However, fish consumption may present risk to human health if contaminated by toxic substances. With the aim of evaluating the content of essential and toxic elements, the techniques of Instrumental Neutron Activation Analysis and Atomic Absorption Spectrometry were used to determine As, Br, Cd, Cl, Co, Cr, Cs, Fe, Hg, K, Mg, Mn, Na, Pb, Rb, Sb, Se and Zn in the edible tissues (fillet) of six of the most consumed fishes at São Paulo city: whitemouth croaker - Micropogonias furnieri (Desmarest, 1823), smooth weakfish - Cynoscion leiarchus (Cuvier, 1830), common snook - Centropomus undecimalis (Bloch, 1792), Brazilian sardine - Sardinella brasiliensis (Steindachner, 1879), bluefish - Pomatomus saltatrix (Linnaeus, 1766) and lebranche mullet - Mugil liza (Valenciennes, 1836). To validate the analytical methods for accuracy, z-score and HorRat values were applied to certified reference materials analyzed under the same conditions of samples. The elements Br, K and Na were determined by two irradiation modalities, and the Student\'s t-test was used to verify whether there were significant differences between the modalities. In the analysis of essential and potentially toxic elements, it was possible to create a database for Br, Cl, Co, Cs, Fe, K, Mg, Mn, Na, Rb, Se and Zn for potential future discussions. In order to assess food safety risks, the levels of As, Cd, Hg and Pb were compared with the Brazilians law and international values. Regarding food safety, Cd and Pb contents were bellow all technical limits used in this study. As for As, most part of this element may be in organic form, therefore the Hg analysis was determinant. In general, there would be no risk in the consumption of Brazilian sardine, smooth weakfish, lebranche mullet, whitemouth croaker and common snook, while for bluefish it was inconclusive.

The use of slotted quartz tube (SQT) as an atom trap in atomic absorption spectrometry (AAS) provides a more stable chemical environment for atomization / the technique is simple and easily applicable in any laboratory. This thesis study involves application of SQT together with some other approaches to thallium determination by AAS. The first stages involve the efforts to improve nebulization efficiency of conventional flame atomic absorption spectrometry (FAAS) with and without the use of SQT. This is achieved by mixing 100 &micro / L of propanol with 500 &micro / L of Tl standard solution using the optimum conditions. By this method, Propanol-SQT-FAAS, 4.49 times enhancement in sensitivity has been obtained with respect to conventional FAAS, method in which the characteristic concentration was calculated as 894 ng/mL. The second stage of investigation is about the use of SQT as an atom trap, AT, preconcentration device for thallium determination. The similar technique has been successfully applied to some other analytes such as Pb, Cd, Bi and Au / detection limits at the level of ng/mL were obtained in the previous studies. In the present work, the analyte atoms are trapped on the inner surface of SQT in the presence of a lean air-acetylene flame for few minutes. After this collection step, a volume of methyl isobutyl ketone, MIBK, amounting to 10-50 microliters is introduced via conventional nebulization / this causes a momentary alteration in the flame composition and thus results in the release of trapped analyte atoms from the quartz surface. This revolatilization step is followed by a rapid atomization and transient signal was obtained. In addition to this method, a novel approach has been investigated where the inner surface of SQT was modified by using a metal coating with low volatility. For this purpose, eight different coating materials which were tungsten, palladium, molybdenum, gold, tantalum, zirconium, titanium and osmium, have been applied to the inner surface of SQT and as osmium was found to be most appropriate one, the rest of the study was continued with Os-Coated-SQT. This modification provided a better surface than quartz alone so that analyte atoms are trapped more efficiently and also released easily. Although the working principle of the Coated-SQT-AT-FAAS method is same with SQT-AT-FAAS, the conditions for SQT-AT-FAAS and Os-Coated-SQT-AT-FAAS methods were optimized seperately. Limit of detections, 3s/m, has been found to be 38 ng/mL and 3.5 ng/mL for these cases, respectively. While the SQT-AT-FAAS method has provided 92 fold enhancement, the Os-Coated-SQT-AT-FAAS method has provided a 319 fold sensitivity improvement with respect to conventional FAAS method.

This work deals with the determination of metals in soils taken close to the railway. Copper, zinc, nickel and chromium were selected as indicators of the environment contamination. Samples were taken from three localities in South Bohemia. These localities were chosen on the basis of different types of railway tracks (electrified and nonelectrified) and different frequency of train connection. Atomic absorption spectrometry was used for the determination of the metals. An AAS Thermo Scientific iCE 3500 spectrometer served to determine individual analytes. The highest level of copper pollution was detected for samples taken close to the railway with electrified track and with high frequency of train connection. The highest Cu concentration (66.30 mg/kg) was determined in the soil sample from 20cm depth. The highest level of zinc pollution was detected for samples taken in the distance of 3 m from the railway with electrified track and with high frequency of train connection. The highest Zn concentration (641.77 mg/kg) was determined in the soil sample from 30cm depth. The highest concentrations of other metals (Ni and Cr) were detected for the railway with nonelectrified track and with low frequency of train connection. The highest concentrations of Ni and Cr were 21.89 and 54.89 mg/kg, respectively. These concentrations were obtained for samples taken close to the railway.

Made available in DSpace on 2014-06-11T19:27:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-15Bitstream added on 2014-06-13T20:36:06Z : No. of bitstreams: 1 santos_fa_me_botfmvz.pdf: 1235942 bytes, checksum: 7b3f579b06b2874c741bde8ef170587e (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / O presente trabalho teve como objetivo investigar a presença de manganês e zinco em “spots” protéicos de amostras de plasma de tilápia do Nilo (Oreochromis niloticus) obtidos após separação das proteínas por eletroforese em gel de poliacrilamida em segunda dimensão (2D-PAGE) para posterior avaliação qualitativa e quantitativa utilizando fluorescência de raios-X com radiação síncrotron (SR-XRF) e espectrometria de absorção atômica em chama e em forno de grafite (FAAS/GFAAS). As análises dos espectros de fluorescência indicaram a presença de manganês e zinco em quatro e seis “spots” protéicos de plasma, respectivamente. Observou-se que os íons metálicos estão ligados em proteínas com massa molar na faixa de 19 a 70 kDa e com pI na faixa de 4,7 a 6,30. A concentração de manganês e zinco ligados a essas proteínas foi determinada por GFAAS após a mineralização ácida dos spots protéicos, encontrandose concentrações na faixa de 3,40 a 4,20 mg g-1 e 2,30 a 13,90 mg g-1, respectivamente / The aim of the present study was to investigate the presence of manganese and zinc in protein spots in samples of Nile tilapia (Oreochromis niloticus) plasma obtained after protein separation by two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and subsequent qualitative and quantitative determination by synchrotron radiation X-ray fluorescence (SRXRF) and graphite furnace atomic absorption spectrometry (GFAAS). An analysis of the fluorescence spectra indicated the presence of manganese and zinc in four and six plasma protein spots, respectively. It was observed that the metal ions are bound in proteins with molecular weight ranging from 19 to 70 kDa and pI ranging from 4.7 to 6.30. The manganese and zinc concentrations bound to these proteins were determined by GFAAS after acid digestion of protein spots, finding concentrations ranging from 3.40 to 4.20 mg g-1 and 2.30 to 13.90 mg g - 1, respectively