This thesis focuses on developing a new method to measure trace tellurium (Te) in different environmental samples such as lake waters, mine tailings and sediments. The developed technique is based on Hydride Generation Atomic Fluorescence Spectroscopy (HG-AFS), a technique that can measure low concentration of Te and also allows for Te speciation at low cost and high efficiency in various environmental samples. To validate the method that could be used to determine Te speciation in various types of environmental samples, a series of tests has been designed for finding the best conditions to measure Te(IV) using HG-AFS and obtain accurate and reliable results. Those tests include the stability of the signal, the acidity of the solution, the volatility of Te after digestion of solids, the reduction from Te(VI) to Te(IV), the detection limit of the technique, and the validity of two digestion methods under the optimum (HG-AFS) instrumental settings. An interference study including the most common elements in the Earth’s crust such as (Ni, Fe, Pb, Cr, Cu, Co, Zn, Mn and Mo) was also performed. The results of this study showed that Cu(II) can severely interfere with Te quantification decreasing the Te signal to almost zero. Therefore, different masking agents such as 8-hydroxyquinoline, 1,10-phenanthroline, urea and thiourea were tested to reduce and eliminate this interference.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-10-21T14:15:47Z No. of bitstreams: 1 Tese - Dannuza Cavalcante.pdf: 1879788 bytes, checksum: 0fd9cc5ca387348e35095d0c92a17183 (MD5) / Approved for entry into archive by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-10-29T17:23:53Z (GMT) No. of bitstreams: 1 Tese - Dannuza Cavalcante.pdf: 1879788 bytes, checksum: 0fd9cc5ca387348e35095d0c92a17183 (MD5) / Made available in DSpace on 2014-10-29T17:23:53Z (GMT). No. of bitstreams: 1 Tese - Dannuza Cavalcante.pdf: 1879788 bytes, checksum: 0fd9cc5ca387348e35095d0c92a17183 (MD5) / CNPq / Neste trabalho que está no âmbito do PRONEX, foram desenvolvidas estratégias analíticas para a determinação de arsênio e selênio em amostras de alimentos por HG AFS. Foram realizados três trabalhos distintos. O primeiro consistiu no emprego da amostragem e m suspenção para determinação de arsênio em amostras de arroz. Procedimentos de amostragem de suspensão foram avaliados para determinação de As por geração de hidreto acoplado a AFS, usando HNO 3 e sonicação por 30 min. As amostras foram preparadas com KI e m ácido ascórbico e com HCl 6 mol L - 1 , para determinação As total. A exatidão foi confirmada por análise do material de referência certificado NIES SRM 10b de farinha de arroz, a precisão foi confirma com valores de RSD abaixo de 5,9 % e limites de detecçã o e quantificação de 0,91 e 3,04 ng L - 1 , respectivamente. Este método foi utilizado para determinar o teor de arsênio em 24 amostras de arroz que foram adquiridas em supermercados da cidade de Salvador, Bahia, Brasil. O conteúdo de arsênio nos três tipos de arroz (branco, parbolizado e integral) variou de 0,12 a 0,47 μg g - 1 . O segundo trabalho foi o desenvolvimento de método analítico para determinação de selênio em ovos. Três tipos de ovos foram adquiridos (codorna, galinha e pata) em feiras e supermercad os de Salvador. A digestão foi realizada mediante adição de HNO 3, H 2 O 2 30% v v - 1 e HCl 6 mol L - 1 , utilizando o bloco digestor com dedo frio. As condições para a pré - redução e geração do hidreto de selênio foram otimizadas empregando o planejamento fatorial e a matriz de Doehlert. As condições ótimas foram: concentração de HCL 5,3 mol L - 1 , concentração do borohidreto de sódio 2,6 % (m/v), volume de KBr 10% 1,0 mL e tempo de pré - redução de 30 min. O método apresentou limites de detecção e quantificação de 0,22 e 0,77 ng L - 1 , respectivamente. O RSD ficou abaixo de 4,7 % demonstrando boa repetibilidade. A exatidão foi comprovada através da análise do CRM de tecido de ostra e também através de comparação com resultados obtidos e m análise no ICP - MS. O método foi aplicado em quatro diferentes grupos de amostras, na clara e na gema separadas e na mistura dos dois, sendo que as concentrações mínimas e máximas foram de 0,35 ± 0,01 a 0,88 ± 0,03 μg g - 1 . O terceiro trabalho foi o desenv olvimento de método para determinação de arsênio em atum e sardinha enlatados. As amostras foram submetidas a 3 procedimentos de preparo de amostra (bloco digestor, forno de micro - ondas e forno mufla). As condições para a pré - redução e geração do hidreto d e arsênio foram otimizadas empregando o planejamento fatorial e a matrix de Doehlert e as condições encontradas foram: tempo de pré - redução de 21 min, volume de pré - redutor KI 10 % (m v - 1 ) em ácido ascórbico 2% (m v - 1 ) de 1,0 mL, concentração de HCl 4,7 mo l L - 1 e concentração de NaBH 4 de 2% (m v - 1 ). O método mostrou - se preciso, com valores de RSD abaixo de 7,0 %. Um material de referência certificado de tecido de ostra (NIST SRM 1566b) foi analisado para avaliar a exatidão do método. O material foi submetid o a três procedimentos de digestão. Através da análise dos resultados pode - se observar que o valor obtido no forno de micro - ondas e no bloco digestor foi cerca de metade do valor certificado, pois a arsenobetaina só é convertida a arsênio inorgânico a temp eraturas acima de 300 º C. O método foi aplicado para 20 amostras de atum e sardinha enlatados e os valores de concentração variaram de: 0,63 ± 0,10 a 3,28 ± 0,20 μg g - 1 / In this work is under PRONEX , strategies for analytical determination of arsenic and selenium in food samples by HG AFS were developed. Three diferent studies were conducted. The first one consisted in the use of sampling in suspension for determination of arsenic in rice procedures were evaluated to As by hydride generation coupled to AFS using HNO 3 and sonication for 30 min. The samples were prepared with KI in ascorbic acid and 6 mol L - 1 HCl to determine total As . The accuracy was confirmed by analysis of certified reference material NIES SRM 10b rice flour , precision was confirmed with % RSD values lower than 5.9% and limits of detection and quantification of 0. 91 and 3.04 ng L - 1 , respectively. This method was used t o determine the content of arsenic in 24 rice samples purchased at supermarkets in the city of Salvador , Bahia , Brazil . The content of arsenic in the three types of rice ( white, parboiled and integral ) ranged from 0.12 to 0.47 μ g g - 1 . In the second study we developed a method for determination of selenium in eggs. Three types of eggs were purchased ( quail, chicken and paw) at fairs and supermarkets of Salvador . The digestion was performed by adding HNO 3 , 30% H 2 O 2 ( v v - 1 ) , 6 mol L - 1 HCI and , using the block digester cold finger. The conditions for the pre - reduction and hydride generation of selenium were optimized using factorial design and Doehlert matrix, the optimal conditions were : HCl concentration of 5.3 mol L - 1 , the 2.6 % ( w v - 1 ) sodium borohydride concentration , 1.0 mL volume of 10% ( w v - 1 ) KBr and pre - reduction time 30 min. The method has limits of detection and quantification of 0.2 2 and 0.7 7 ng L - 1 , respectively. The % RSD was below 4.7 showing good repeatability . The accuracy was confirmed by analysis of CRM oyster tissue and also by comparison with results obtained for analysis by ICP - MS. The method was applied to four different groups of samples , in clear and separate yolk and mix of the two , the minimum and maximum concentrations were 0.35 ± 0.01 to 0.88 ± 0.03 mg g - 1 . The third work was the development of a method for determination of arsenic in canned tuna and sardines . The samples were subjected to three procedures for sample preparation ( digestion block, microwave and oven muffle ). The co nditions for the pre - reduction and hydride generation of arsenic were optimized using factorial design matrix and Doehlert , the conditions were: pre - reduction time of 21 min, volume of 1.0 mL of 10% KI ( w v - 1 ) (pre - reducing) in 2% a scorbic acid, HCl concentration of 4.7 mol L - 1 and NaBH 4 - in 2% ( v m - 1 ). The method was precise, with RSD values below 7.0 %. A certified reference material of oyster tissue ( NIST SRM 1566b ) was analyzed to assess the accuracy of the method . The material was subjected to the three digestion procedure. From t he analysis of the results it can be seen that the value obtained in the microwave oven and the digester block was about half the value of the certificate , as the only arsenobetaine is converted to inorganic arsenic at temperatures above 300 °C. The method was applied to 20 samples of canned tuna and sardines and concentration values ranged from 0.63 ± 0.1 0 to 3.28 ± 0.2 0 mg g - 1

Orogenic gold deposits occur within metamorphic belts throughout the world and have through time represented the source for over 25% of the world’s gold production. Although orogenic gold deposits are of great economic importance, controversies exist on the subject of fluid and metal sources and there have been few studies of gold´s distribution and mobility outside of large economic deposits. Research made by Pitcairn et al. (2006), on the Mesozoic Otago and Alpine schists of New Zealand, observed systematic depletion of Au and a suite of 6 associated elements with increasing metamorphic grade. This depletion was identical to the suite of elements enriched in the Otago gold deposits and provided strong evidence that orogenic gold deposits form due to metamorphic processes. The mobilization of metals was attributed to the recrystallization of sulfide minerals during prograde metamorphism causing dehydration and release of metal-rich metamorphic fluids.  This thesis is part of a larger project aimed at testing the “Otago model” in a classic metamorphic terrain: The Dalradian metamorphic belt of Scotland. Rocks in the study are from the southern higlands group and the Appin and Argyll group which range in metamorphic grade from chlorite zone greenschist facies to sillimanite zone amphibolite facies. Three main aspects, which supplement earlier research, are addressed in this study: 1) Investigation of the sulfide paragenesis at Loch Lomond and Stonehaven was carried out to map the evolution of sulfides with metamorphic grade and the possible relations to the distribution of gold. Using SEM scanning to quantify the abundance of different sulfide minerals together with previous data on the Glen Esk region, a complex sulfide evolution pattern for the Dalradian Supergroup is identified. The sulfide evolution describes the same changes in texture and chemistry as observed in the Otago Schists but is made complex by the difference in geological evolution for the different regions. 2) Reinvestigation of the higher grade zones of Glen Esk (staurolite to sillimanite) was carried out as samples from the previous study were very weathered. Results from ultralow detection limit methods (HG-AFS and a gold detection method developed by Pitcairn et al. 2006) showed significant systematic depletion of Au and As with metamorphic grade. From chlorite to sillimanite zone average values of Au and As were showed to decrease by 65% and 88% respectively. Furthermore, a suite of 10 major and 12 trace elements were analyzed using ICP methods showing no trends of systematic depletion with increased metamorphic grade.  3) Investigation of Pb-Ag Veining and vein samples from each of the metamorphic index mineral zones in the Glen Esk area was carried out to identify fluid composition and ore mineralogy. Using microthermometry and Raman laser spectroscopy two distinct fluids were identified. The first type is a H2O-CO2-N2-salt fluid of low salinity (0-15 weight percent NaCl equivalent) and medium temperature (150 to 250 °C) locally containing minor amounts of CH4. It is found in the veins from the mineral index zones of Glen Esk and was formed in the ductile regime most likely related to late stage metamorphic devolatilization released during Caledonian uplift of the Dalradian. Pb-Ag veins from the locality of Hardhill host the second fluid type which was formed in the brittle regime  accompanied by brecciation as a high salinity (15 to 20 weight percent NaCl equivalent) low temperature (70-140°C) H2O-salt fluid with calcic composition was precipitated. This fluid bears much resemblance to Carboniferous calcic brines responsible for economic base-metal precipitation with widespread occurrence in southwest Scotland and Northern Ireland. Results of this thesis show many similarities with the Otago study, with a connection between metal mobility and metamorphic grade, providing support for the dehydration model as a viable mechanism for the generation of orogenic gold deposits.