Orientador: Juliana Azevedo Lima-Pallone / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-20T21:26:18Z (GMT). No. of bitstreams: 1 Rebellato_AnaPaula_M.pdf: 1287593 bytes, checksum: 661e828d074dab6ac68c3fad61029313 (MD5) Previous issue date: 2012 / Resumo: No Brasil a ANVISA através da Resolução nº 344 de 2002, instituiu a obrigatoriedade do enriquecimento de farinhas de trigo e milho com ácido fólico e ferro. A deficiência de ferro é apontada como a principal causa da anemia ferropriva. A fortificação de alimentos com ferro é a estratégia indicada pelas instituições que atuam na área de saúde como a mais eficiente para o combate à anemia. Entretanto, a ingestão excessiva deste mineral está associada a danos oxidativos e tem sido relacionada com a manifestação de várias doenças. Dessa forma, o alcance dos objetivos dos programas de fortificação de alimentos está relacionado à garantia da ingestão recomendada para os nutrientes adicionados e aos atributos físico-químicos, que devem ser monitorados no veículo utilizado e no produto final. Este trabalho teve como objetivos adequar e validar uma metodologia para a determinação de ferro em amostras de biscoitos elaborados com farinha de trigo fortificada, utilizando a técnica de Espectrometria de Absorção Atômica com chama e acompanhar os parâmetros físico-químicos (umidade, acidez, índice de peróxido e teor de lipídeos) durante o período de estocagem (150 dias). O método para determinação do teor de ferro em biscoitos foi validado para os parâmetros precisão, seletividade, recuperação, sensibilidade, linearidade, limite de detecção (LD) e limite de quantificação (LQ) e se mostrou adequado. O teor médio de ferro presente nos biscoitos tipo cream cracker, água e sal, maisena e amanteigado foram: 5,0 a 8,6; 5,3 a 7,8; 2,5 a 6,8; 3,7 a 5,7 mg 100 g-1, respectivamente. Foi verificada diferença significativa entre lotes de mesma marca e entre marcas do mesmo tipo, através da ANOVA e do Teste de Tukey (p<0,05). Para os parâmetros físico-químicos, os valores obtidos ao longo do período de estocagem variaram; umidade de 1,8 a 6,3%; acidez de 1,5 a 7,4 mg NaOH 0,1 mol L-1 100g-1; índice de peróxido de valor não detectado (nd) a 95,1 meq Kg-1 de gordura. Para o teor de lipídeos e ferro, o menor e o maior valor encontrado foram 9,8 e 18,0% e 2,1 e 9,2 mg 100 g-1, respectivamente. Foi possível verificar que existe diferença significativa entre os valores obtidos para cada lote de mesma marca ao longo do período de estocagem. Nenhum tipo de correlação entre a umidade e os valores de acidez presentes nas matrizes, foi observado, da mesma forma que não foi verificada nenhuma correlação entre o índice de peróxido e o teor de ferro. Notou-se que há necessidade de melhorar a qualidade dos ingredientes utilizados no preparo dos biscoitos a fim de manter um padrão de qualidade uniforme durante todo o período de validade. As variações observadas no teor de ferro indica a necessidade de uma legislação mais específica, estabelecendo concentrações (mínima e máxima) para o mineral utilizado na fortificação de farinha de trigo que estará presente em alimentos prontos para o consumo, a fim de garantir o sucesso da campanha de fortificação / Abstract: Through the resolution no. 344 of 2002, ANVISA (Brazilian Regulatory Institute) assigned the obligation of enriching wheat and corn flours with folic acid and iron. Iron deficiency is pointed out as the main cause of anemia, so food fortification with this mineral is the most efficient strategy indicated by the health institutions that work towards the combat of anemia. However, excessive ingestion of this mineral is associated with oxidative damages and has also been related to the occurrence of several diseases. So the fortification programs must guarantee the recommended intake, and not more than that, as well as to maintain the physicochemical attributes, by monitoring both the vehicle of fortification and the final product. This work redesigned and validated one methodology for iron determination in samples of biscuits produced with fortified wheat flour, by using Flame Atomic Absorption Spectrometry (FAAS). It also measured physicochemical parameters (moisture, acidity, peroxide index and fat content) during the storage period (150 days). The method for iron determination in biscuits is shown to be adequate and was validated for the parameters precision, sensibility, selectivity, recovery, accuracy, linearity, limit of detection (LOD) and quantification (LOQ). The iron content in biscuits of the types cream cracker, salt and water, cornstarch cookies (maizena) and butter cookies were, respectively: 5.0 to 8.6, 5.3 to 7.8, 2.5 to 6.8, and 3.7 to 5.7 mg 100 g-1. ANOVA and Tukey tests (p<0,05) were applied to verify if there was significant difference between batches of the same brand and among the brands of the same type of biscuits. For the physicochemical parameters, all the values obtained throughout the storage period varied. Moisture was from 1.8 to 6.3%; acidity was from 1.5 to 7.4 mg NaOH (0,1 mol.L-1) 100 g-1; peroxide index was form non-detectable (nd) to 95.1 meq Kg-1 of fat. The lowest and the highest values for fat content were 9.8 and 18% the range for iron was from 2.1 to 9.2 mg 100 g-1 for iron. There was significant difference between the values obtained for each batch of the same brand throughout the storage period. But there was no correlation between the moisture present in the matrix and the acidity values, neither there was between the peroxide index and iron content. It is necessary for the industries of biscuits to improve the stability of the ingredients to maintain uniformity during all the storage period. The observed variation of iron content indicates the need for a more specific legislation, which establishes minimum and maximum concentrations for the mineral added to fortify wheat flour, aiming to guarantee the success of the fortification campaign / Mestrado / Ciência de Alimentos / Mestra em Ciência de Alimentos

Flame Atomic Absorption Spectrometry (FAAS) still keeps its importance despite the relatively low sensitivity / because it is a simple and economical technique for determination of metals. In recent years atom traps have been developed to increase the sensitivity of FAAS. Although the detection limit of FAAS is only at the level of mg/L, with the use of atom traps it can reach to ng/mL. Slotted quartz tube (SQT) is one of these atom traps, it is applied for determination of volatile elements / it is economical, commercially available and easy to use. In this study, a sensitive analytical method has been developed for the determination of lead with the help of SQT. Regarding the angle between the two slots of SQT, 120&deg / and 180&deg / configurations were used and the results were compared. There were three modes of SQT used. The first application was for providing longer residence time of analyte atoms in the measurement zone / 3 fold sensitivity enhancement was observed. The second mode was the usage of SQT for preconcentration of lead atoms. In the presence of a lean air-acetylene flame, analyte atoms were trapped in the inner surface of SQT for a few minutes. Then, by the help of a small volume (10-50 &amp / #956 / L) of Methyl isobutyl ketone (MIBK), analyte atoms were revolatilized and a rapid atomization took place. Using this mode, a sensitivity enhancement of 574 was obtained at a rather low (3.9 mL/min) suction rate / 1320 fold improvement was reached at higher sample suction rate (7.4 mL/min) for 5.0 min collection. The last mode involves coating of the inner surface of SQT with several kinds of transition metals. The best sensitivity enhancement, 1650 fold, was obtained by the Ta coated SQT. In addition, effects of some elements and anions on Pb signal in Tacoated-SQT-AT-FAAS were examined. Final step consists of surface analysis / chemical nature of Pb trapped on quartz and Ta surface, and the chemical nature of Ta on quartz surface were investigated by X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy.

ABSTRACT DETERMINATION OF CADMIUM USING SLOTTED QUARTZ TUBE ATOM TRAP ATOMIC ABSORPTION SPECTROMETRY AND METAL COATINGS &Ouml / zcan Gurbetoglu, G. Pelin M.S., Department of Chemistry Supervisor: Prof. Dr. O. Yavuz Ataman July 2010, 76 pages Flame atomic absorption spectroscopy (FAAS) is a common technique for detecting metals and metalloids in environmental, biological and metallurgical samples. Although it is a rather old technique, it is still very reliable, simple to use and inexpensive. The technique can be used to determine the concentration of over 70 different metals in a solution. However, it has detection limits at mg/L levels. Some atom trapping methods have been developed to reach the detection limits of ng/mL levels. Slotted quartz tube (SQT) is one of these atom trapping methods. It is an important technique, since it is easy to use, applicable in all laboratories, commercially available and economical. This thesis consists of development of a sensitive method for cadmium with the help of SQT atom trap. In this study, it was used for two different purposes. One was for keeping the analyte atoms more in the light path / in other words, for increasing the residence times of analyte atoms in the measurement zone. This first application was provided a 2.9 times enhancement with respect to conventional FAAS. Second application was for trapping the analyte on the surface of the SQT, in other words, for performing on-line preconcentration of cadmium in SQT. In the presence of a lean flame, analyte samples were trapped and collected for a few minutes at a low suction rate. After finishing the collection period, analyte atoms were revolatilized with the help of a small volume of (10-50 &micro / L) methyl isobutyl ketone (MIBK) and a rapid atomization occurred. This introduction also altered the flame composition momentarily and analyte atoms were released from the surface of the SQT. Application of this method enhanced the sensitivity 2065 times with respect to conventional FAAS. Another approach to this type of atom trapping has been investigated also in this study, which was coating of SQT with some metals having low volatility. Therefore, some transition metals were coated to the surface of SQT and among them zirconium was selected as the best coating material as having the most sensitivity enhancement factor. That is why, rest of the study was performed with the Zr coated SQT. The enhancement was 3368 as compared with FAAS. Cd determination with this method provides LOD value of 8 pg/mL and Co value of 19 pg/mL. In order to see the effect of some other type of elements or ions on determination of cadmium, interference study was done.

Flame Atomic Absorption Spectroscopy (FAAS) has lover sensitivity than similar analytical methods, however it has an important place for analysis due to its easy application and economic practicability especially in metal determinations. In order to increase the sensitivity of FAAS from mg/L level to ng/L level, various atom trap systems have been used. One of these atom traps, Slotted Quartz Tube (SQT), which is easy, economical and useful for volatile element determination, is used in this study as a sensitive analytical method for determination of tellurium. In the study, determination of Te by SQT is handled in three different modules. First, only with SQT itself, longer residence time for Te atoms in the measurement zone is provided and consequently 3.2 fold sensitivity enhancement is obtained both for Te (VI) and Te (IV). In the second module, SQT is used for concentration of tellurium species in a lean flame by sending the analyte into SQT for a definite time and trapping them on the inner surface of the SQT. After trapping the analyte, in order to determine the Te concentration, a small volume (10-50 &micro / L) of organic solvent such as methyl ethyl ketone (MEK) is introduced to the flame for revolatilization and a rapid atomization of Te on the surface is provided. In this trapping method, for 5 minutes collection with a 6 mL/min suction rate, 143 fold enhancement for Te (VI) and 142 fold enhancement for Te (IV) were obtained. In the third module, different from the second one, the inner surface of the SQT is coated with different metals for increasing the amount of Te trapped on the surface and the best enhancement for tellurium is obtained with Tantalum-coated SQT with 252 fold enhancement for Te (VI) and 246 fold enhancements for Te (IV). All improvements are calculated according to the signals obtained in FAAS method. Separate calibration plots were used for Te (IV) and Te (VI).

Silver is a precious metal having antibacterial property and widely used in industry mostly for water purification and medicinal products. Therefore, the determination of trace levels of silver is important for industrial applications. Flame atomic absorption spectrometry (FAAS) is a popular technique for the determination of relatively low concentration levels. This mature technique owes its widespread application to its simplicity and low cost. However, for some occasions, FAAS technique suffers from its low sensitivity because of low nebulization efficiency and relatively short residence time of analyte atoms in the measurement zone. In order to overcome this sensitivity problem, atom traps have been developed in recent years. Slotted quartz tube (SQT) is an accessory designed to use as an atom trap in conventional flame atomic absorption burner head. This thesis study involves the development of a sensitive, simple and economical technique with the help of the SQT for the determination silver. Firstly, the technique known as SQT-FAAS was used to increase the residence time of analyte atoms in the measurement zone. In this case, limit of detection (LOD) and characteristic concentration (C0) values were found to be 19 ng/mL and 35 ng/mL, respectively. Enhancement in sensitivity with respect to FAAS was found to be 2.31 fold using SQT-FAAS. Regarding the angle between the two slots of the SQT, 180&deg / configuration was used. Secondly, in order to improve sensitivity further, the SQT was used as an atom trap (AT) where the analyte is accumulated in its inner wall prior to re-atomization. The signal is formed after reatomization of analyte atoms on the trap surface by introduction of organic solvent. For this purpose, uncoated SQT was used as a trap medium. However, there was a memory effect. Therefore, the SQT inner surface was coated with different coating elements and theoptimum conditions were found by using W-coated SQT-AT-FAAS technique. In the presence of a lean air-acetylene flame, analyte atoms were trapped in the inner surface of the SQT for 5.0 min and then revolatilized with the introduction of 25 &mu / L isobutyl methyl ketone (IBMK) / afterwards, a transient signal was obtained. These optimized parameters were used for uncoated SQT, W-coated SQT and Zr-coated SQT atom trap techniques. Sample suction rate was 6.25 mL/min in all techniques. Sensitivity was increased 54 fold using uncoated SQT-AT-FAAS technique with respect to simple FAAS technique. When W-coated SQT-AT-FAAS technique was applied, 135 fold sensitivity enhancement was obtained with respect to FAAS technique. The best sensitivity enhancement, 270 fold, was obtained using Zr-coated SQT-AT-FAAS technique. In addition, the Ag signals were more reproducible (%RSD, 1.21) when Zr was used as a coating element. After the sensitive technique was developed, interference effects of some transition and noble metals and hydride forming elements on Ag signals were investigated. Finally, surface studies were done to determine the chemical state of Ag during trapping period by using X-ray Photoelectron Spectroscopy (XPS). It was observed that the Ag analyte is retained on the SQT surface in its oxide form.

Orientador: Juliana Azevedo Lima Pallone / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-22T00:01:01Z (GMT). No. of bitstreams: 1 Oliveira_AnaAliceAndrade_M.pdf: 1712746 bytes, checksum: f7bd6bb2cad0015ebc180af686268e60 (MD5) Previous issue date: 2013 / Resumo: A partir da Resolução Nº 344, de 13 de dezembro de 2002, publicada pela Agência Nacional de Vigilância Sanitária, a fortificação de farinhas de trigo e milho com ferro e ácido fólico tornou-se obrigatória. No entanto, para garantir a eficiência do programa de fortificação, é importante obter dados sobre o consumo de ferro a partir dos alimentos fortificados e assegurar a qualidade destes produtos. Neste trabalho foi validada e aplicada uma metodologia para determinação de ferro por espectrometria de absorção atômica com chama em massas e bolos elaborados com farinha de trigo fortificada. Também foram realizadas determinações de umidade, acidez álcool solúvel e índice de peróxido, a fim de verificar a qualidade destes produtos. O teor de carbono residual nas amostras, após mineralização, foi determinado por espectrometria de emissão atômica por plasma indutivamente acoplado (ICP-OES). Os resultados revelaram que a digestão foi eficiente e que o método para determinação de ferro apresenta precisão, exatidão, linearidade e limites de detecção e quantificação adequados para aplicação em massas e bolos. Os resultados da determinação de ferro mostraram que, entre as amostras de macarrão massa seca, macarrão instantâneo, massa de pizza, massa de pastel, bolo e massa de lasanha o teor de ferro variou de 2,5 a 7,1 mg 100 g-1 (em média 5,0 mg 100 g-1), de 2,4 a 5,5 mg 100 g-1 (em média 4,3 mg 100 g-1), de 2,0 a 5,5 mg 100 g-1 (em média 3,8 mg 100 g-1), de 1,0 a 4,9 mg 100 g-1 (em média 2,9 mg 100 g-1), de 1,1 a 3,1 mg 100 g-1 (em média 2,1 mg 100 g-1) e de 0,7 a 4,7 mg 100 g-1 (em média 2,9 mg 100 g-1), respectivamente. Para o macarrão massa seca, macarrão instantâneo, massa de pizza, massa de pastel, massa de lasanha e bolo o teor de umidade variou de 9,5% a 12,3%, de 3,3% a 7,1%, de 19,5% e 29,6%, de 25,7% a 31,3%, de 26,6% a 33,1% e de 16,3% a 26,5%, respectivamente. Nas amostras de macarrão massa seca, macarrão instantâneo, massa de pizza, massa de pastel, massa de lasanha e bolo a acidez variou de 1,4 a 3,2 mL de solução 1 mol L-1 de NaOH 100 g-1, de 0,3 e 1,0 mL de solução 1 mol L-1 de NaOH 100 g-1, de 2,9 e 4,6 mL de solução 1mol L-1 de NaOH 100 g-1, de 0,9 e 6,6 mL de solução 1mol L-1 de NaOH 100 g-1, de 1,7 e 3,7 mL de solução 1 mol L-1 de NaOH 100 g-1 e de 1,3 a 2,5 mL de solução 1mol L-1 de NaOH 100 g-1. Nas amostras de macarrão instantâneo o índice de peróxido variou, em média, de 5,9 mEq kg-1 de gordura a 8,4 mEq kg-1 de gordura. Os resultados revelam que as amostras apresentam boa qualidade físico-química, entretanto, notou-se grande variação no teor de ferro nas amostras analisadas / Abstract: Brazilian Health Surveillance Agency (ANVISA) established, by resolution RDC Nº344, mandatory fortification of wheat flour and corn flour with iron and folic acid. However, to ensure the efficiency of the fortification program, it is important to get information about iron consumption from fortified food and guarantee the quality of the products. The aim of this study was to validate and apply a methodology for iron determination by flame atomic absorption in pasta and cake produced with wheat flour fortified with iron. In addition, humidity, acidity and peroxide index were determined to check the quality of the products. In order to assess the efficiency of the mineralization, residual carbon was determined by inductively-coupled plasma optical emission spectrometry. The results revealed that the mineralization was efficient and the method demonstrated accuracy, precision, linearity and adequate detection limit and quantification limit. The results of iron determination showed that the iron content of dried pasta, instant noodle, pizza dough, samosa dough, orange cake and fresh lasagna sheets ranged from 2,5 to 7,1 mg 100 g-1 (on average 5,0 mg 100 g-1), from 2,4 to 5,5 mg 100 g-1 (on average 4,3 mg 100 g-1), from 2,0 mg 100 g-1 to 5,5 mg 100 g-1 (on average 3,8 mg 100 g-1), from 1,0 to 4,9 mg 100 g-1 (on average 2,9 mg 100 g-1), from 1,1 to 3,1 mg 100 g-1 (on average 2,1 mg 100 g-1) and from 0,7 to 4,7 mg 100 g-1 (on average 2,9 mg 100 g-1),respectively. The humidity of dried pasta, instant noodle, pizza dough, samosa dough, pizza dough, fresh lasagna sheets and orange cake ranged from 9,5% to 12,3%, from 3,3% to 7,1%, from 19,5% e 29,6%, from 25,7% to 31,3%, from 26,6% to 33,1% e from 16,3% to 26,5%, respectively. The acidity of dried pasta, instant noodle, pizza dough, samosa dough, fresh lasagna sheets and orange cake ranged from 1,4 to 3,2 mL of 1 mol L-1 NaOH solution 100 g-1, from 0,3 to 1,0 mL of 1 mol L-1 NaOH solution 100 g-1, from 2,9 to 4,6 mL 1mol L-1 NaOH solution 100 g-1, from 0,9 to 6,6 mL 1mol L-1 NaOH solution 100 g-1, from 1,7 to 3,7 mL de solução 1 mol L-1 de NaOH 100 g-1 and from 1,3 to 2,5 mL 1mol L-1 NaOH solution 100 g-1, respectively. The peroxide index of instant noodle ranged from 4,0 mEq kg-1 to 12,0 mEq kg-1. The results reveal that samples had good physicochemical quality, however there was a wide variation in the products / Mestrado / Ciência de Alimentos / Mestra em Ciência de Alimentos

Um procedimento de separação e pré-concentração em sistemas de análises em fluxo acoplado a espectrometria de absorção atômica com atomização em chama (FI-FAAS) é proposto para a determinação de Cu(II), Ni(II) e Cd(II). Diferentes adsorventes (XAD-7, sílica-gel e sílica funcionalizada C18) foram avaliados para a imobilização do reagente 1-(2-tiazolilazo)-2-naftol (TAN) que forma complexos com diversos íons metálicos. A avaliação e seleção do adsorvente baseou-se em isotermas de adsorção (Langmuir, Freundlich e Dubinin- Radushkevich (D-R)) e estudos de dessorção. O modelo de Langmuir indicou que a -2 -1 sílica-gel adsorve uma quantidade maior de TAN (1,81±0,08)x10-2 g g-1 em relação à XAD-7 (4,05±0,51)x10-3 g g-1 e à sílica funcionalizada C18 1,58x10-2 g g-1 . Pelo modelo de Freundlich, foi verificado que a superfície da XAD-7 apresenta elevada heterogeneidade energética dos sítios de adsorção evidenciado pelo parâmetro n de 2,57±0,08 contra 1,01±0,02 para sílica-gel. A constante de Freundlich foi de -1 (0,232±0,023) e (2,27±0,59) g g-1 para XAD-7 e sílica-gel, respectivamente. O modelo de D-R revelou que ocorre fisissorção para ambos os adsorventes. Estudos de dessorção permitiram concluir que a XAD-7 modificada apresentou a menor massa de TAN dessorvida em comparação com a sílica-gel, nas condições de acidez a serem empregadas nas etapas de retenção e eluição dos íons metálicos. Desta forma, XAD-7 imobilizada com o TAN foi selecionada para pré-concentração dos metais no sistema de análises em fluxo. Utilizando um amostrador temporizado eletronicamente, as variáveis vazão e concentração do eluente, pH de retenção, vazão e tempo de pré-concentração da amostra foram avaliadas. Na etapa de amostragem, os íons metálicos foram pré-concentrados por 300 s na forma de complexos com o TAN, empregando vazão de amostra de 6,2 mL min-1 e pH 7,5. A eluição foi efetuada com 0,2 mol L-1 HNO3 e vazão de 6,2 mL min-1 . O limite de detecção e o fator de enriquecimento foram estimados em 0,20 µg L-1 e 68; 1,5 µg L-1 e 15 e 0,060 µg L-1 e 44 para Cu(II), Ni(II) e Cd(II), respectivamente. Os coeficientes de variação foram estimados em 3,2%, 5,6% e 3,6% para Cu(II), Ni(II) e Cd(II), respectivamente. O procedimento proposto para FI não é adequado para a pré-concentração de metais em amostras contendo altas concentrações de íons cloreto, devido à formação de cloro-complexos, que prejudicam a formação de complexos com TAN na fase sólida. / A flow-based procedure for separation and preconcentration coupled to flame atomic absorption spectrometry (FI-FAAS) is proposed for determination of Cu(II), Ni(II) e Cd(II). Different sorbents (XAD-7, silica gel and C18 bonded silica) were evaluated for the immobilization of the reagent 1-(2-thiazolylazo)-2-naphthol (TAN), which reacts with several metal ions yielding complexes. The evaluation and selection of the adsorbent was based on adsorption isotherms (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)) as well as desorption studies. The Langmuir model indicated that silica gel uptakes higher amount of TAN (1.81±0.08)x10-2 g g-1 as compared to (4.05±0.51)x10-3 g g-1 for XAD-7 and (1.58x10-2 ) g g-1 for C18 bonded silica. Based on the Freundlich model, it was verified that XAD-7 surface presented high energetic heterogeneity of the adsorption sites evidenced by the parameter n of 2.57±0.08 against 1.01±0.02 to silica gel. The Freundlich constant was 0.232±0.023 -1 and 2.27±0.59 g g-1 for XAD-7 and silica gel, respectively. The D-R model revealed that physical sorption occurred for both adsorbents. The modified XAD-7 showed the lowest desorbed mass in comparison to silica gel, in the same acidity conditions employed for retention and eluting steps of the metal ions. XAD-7 modified with TAN was thus selected to concentrate metal ions in the flow system. Using a time-based sample loading, the variables like eluent flow rate and concentration; pH in the retention step, sample flow rate and loading sample time were investigated. In the sampling step, the metal ions were preconcentrated for 300 s in the form of TAN complexes, employing a sample flow rate of 6.2 mL min-1 and pH 7.5. The elution was carried out with 0.2 mol L-1 HNO3 and flow rate of 6.2 mL min-1 . The detection limits and enrichment factors were estimated as 0.2 µg L-1 and 68; 1.5 µg L-1 and 15 and 0.060 µg L-1 and 44 for Cu(II), Ni(II) and Cd(II), respectively. The coefficients of variation were estimated as 3.2%, 5.6% and 3.6% for Cu(II), Ni(II) and Cd(II), respectively. The proposed procedure is not appropriate for the preconcentration of metals in samples containing high chlorides concentrations due to the formation of chloride-complexes that hinder the formation of the TAN-complexes on the solid phase.

Um procedimento de separação e pré-concentração em sistemas de análises em fluxo acoplado a espectrometria de absorção atômica com atomização em chama (FI-FAAS) é proposto para a determinação de Cu(II), Ni(II) e Cd(II). Diferentes adsorventes (XAD-7, sílica-gel e sílica funcionalizada C18) foram avaliados para a imobilização do reagente 1-(2-tiazolilazo)-2-naftol (TAN) que forma complexos com diversos íons metálicos. A avaliação e seleção do adsorvente baseou-se em isotermas de adsorção (Langmuir, Freundlich e Dubinin- Radushkevich (D-R)) e estudos de dessorção. O modelo de Langmuir indicou que a -2 -1 sílica-gel adsorve uma quantidade maior de TAN (1,81±0,08)x10-2 g g-1 em relação à XAD-7 (4,05±0,51)x10-3 g g-1 e à sílica funcionalizada C18 1,58x10-2 g g-1 . Pelo modelo de Freundlich, foi verificado que a superfície da XAD-7 apresenta elevada heterogeneidade energética dos sítios de adsorção evidenciado pelo parâmetro n de 2,57±0,08 contra 1,01±0,02 para sílica-gel. A constante de Freundlich foi de -1 (0,232±0,023) e (2,27±0,59) g g-1 para XAD-7 e sílica-gel, respectivamente. O modelo de D-R revelou que ocorre fisissorção para ambos os adsorventes. Estudos de dessorção permitiram concluir que a XAD-7 modificada apresentou a menor massa de TAN dessorvida em comparação com a sílica-gel, nas condições de acidez a serem empregadas nas etapas de retenção e eluição dos íons metálicos. Desta forma, XAD-7 imobilizada com o TAN foi selecionada para pré-concentração dos metais no sistema de análises em fluxo. Utilizando um amostrador temporizado eletronicamente, as variáveis vazão e concentração do eluente, pH de retenção, vazão e tempo de pré-concentração da amostra foram avaliadas. Na etapa de amostragem, os íons metálicos foram pré-concentrados por 300 s na forma de complexos com o TAN, empregando vazão de amostra de 6,2 mL min-1 e pH 7,5. A eluição foi efetuada com 0,2 mol L-1 HNO3 e vazão de 6,2 mL min-1 . O limite de detecção e o fator de enriquecimento foram estimados em 0,20 µg L-1 e 68; 1,5 µg L-1 e 15 e 0,060 µg L-1 e 44 para Cu(II), Ni(II) e Cd(II), respectivamente. Os coeficientes de variação foram estimados em 3,2%, 5,6% e 3,6% para Cu(II), Ni(II) e Cd(II), respectivamente. O procedimento proposto para FI não é adequado para a pré-concentração de metais em amostras contendo altas concentrações de íons cloreto, devido à formação de cloro-complexos, que prejudicam a formação de complexos com TAN na fase sólida. / A flow-based procedure for separation and preconcentration coupled to flame atomic absorption spectrometry (FI-FAAS) is proposed for determination of Cu(II), Ni(II) e Cd(II). Different sorbents (XAD-7, silica gel and C18 bonded silica) were evaluated for the immobilization of the reagent 1-(2-thiazolylazo)-2-naphthol (TAN), which reacts with several metal ions yielding complexes. The evaluation and selection of the adsorbent was based on adsorption isotherms (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)) as well as desorption studies. The Langmuir model indicated that silica gel uptakes higher amount of TAN (1.81±0.08)x10-2 g g-1 as compared to (4.05±0.51)x10-3 g g-1 for XAD-7 and (1.58x10-2 ) g g-1 for C18 bonded silica. Based on the Freundlich model, it was verified that XAD-7 surface presented high energetic heterogeneity of the adsorption sites evidenced by the parameter n of 2.57±0.08 against 1.01±0.02 to silica gel. The Freundlich constant was 0.232±0.023 -1 and 2.27±0.59 g g-1 for XAD-7 and silica gel, respectively. The D-R model revealed that physical sorption occurred for both adsorbents. The modified XAD-7 showed the lowest desorbed mass in comparison to silica gel, in the same acidity conditions employed for retention and eluting steps of the metal ions. XAD-7 modified with TAN was thus selected to concentrate metal ions in the flow system. Using a time-based sample loading, the variables like eluent flow rate and concentration; pH in the retention step, sample flow rate and loading sample time were investigated. In the sampling step, the metal ions were preconcentrated for 300 s in the form of TAN complexes, employing a sample flow rate of 6.2 mL min-1 and pH 7.5. The elution was carried out with 0.2 mol L-1 HNO3 and flow rate of 6.2 mL min-1 . The detection limits and enrichment factors were estimated as 0.2 µg L-1 and 68; 1.5 µg L-1 and 15 and 0.060 µg L-1 and 44 for Cu(II), Ni(II) and Cd(II), respectively. The coefficients of variation were estimated as 3.2%, 5.6% and 3.6% for Cu(II), Ni(II) and Cd(II), respectively. The proposed procedure is not appropriate for the preconcentration of metals in samples containing high chlorides concentrations due to the formation of chloride-complexes that hinder the formation of the TAN-complexes on the solid phase.

Made available in DSpace on 2016-08-19T12:56:36Z (GMT). No. of bitstreams: 1 DISSERTACAO Raimunda.pdf: 630410 bytes, checksum: 7da934967ca507178e085597457d69dd (MD5) Previous issue date: 2010-11-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Thinking of the metals sodium, potassium, calcium and magnesium can damage the stability of biodiesel, because they tend to react with esters and to produce soap, this work aimed to carry out a procedure for determination of metals in biodiesel of different matrices by flame atomic absorption spectrometry (F-AAS) using the sample preparation procedure in microwave. For the digestion process, we used the procedure suggested by the equipment for digestion of samples of biodiesel, noting the most important variables in this procedure, such as; time of maximum power, volume of reagents and sample. The levels of sodium, potassium, calcium and magnesium in soybean biodiesel, for instance, were 2925.00 ± 527.89; 164.45 ± 28.27; 306.58± 42.98 e 26.95 ± 3.92 mg Kg-1, respectively. The digestion method proposed was adequate for the preparation of biodiesel samples from different matrices and can be applied for determination of these metals by F-AAS. The method validation was obtained by comparing the method proposed in this work and a procedure that uses sample digestion in microwave oven to determine these metals by ICP-OES. The results obtained by the proposed method were in agreement with results obtained by the proposed method, thereby, the new method is an efficient alternative for the determination of metals in biodiesel, in addition to supplying the deficiencies presented by the method of dilution with solvent. / Tendo em vista que os metais sódio, potássio, cálcio e magnésio podem danificar a estabilidade do biodiesel, pois tendem a reagir com ésteres e produzir sabão, o presente trabalho teve como objetivo realizar um procedimento alternativo para determinação de metais em biodiesel de diferentes matrizes por espectrometria de absorção atômica com chama (F-AAS) utilizando o preparo da amostra em forno de microondas. Para o processo de digestão, foi utilizado o procedimento sugerido pelo equipamento para digestão de amostras de biodiesel, observando as variáveis de maior importância neste procedimento, tais como; tempo de potência máxima, volume dos reagentes e da amostra. Os teores de sódio, potássio, cálcio e magnésio no biodiesel de soja, por exemplo, foram 2925,00 ± 527,89; 164,45 ± 28,27; 306,58± 42,98 e 26,95 ± 3,92 mg Kg-1, respectivamente. O método de digestão proposto mostrou-se adequado para o preparo de amostras de biodiesel de diferentes matrizes, podendo ser aplicado para determinação destes metais por F-AAS. A validação do método foi obtida através da comparação entre o método proposto no presente trabalho e um procedimento que utiliza digestão da amostra em forno de microondas para determinar estes metais por ICP-OES. Os resultados obtidos pelo método proposto foram concordantes com os resultados obtidos pelo método proposto, deste modo, o novo método é uma eficiente alternativa para a determinação de metais em biodiesel, além de suprir as deficiências apresentadas pelo método de diluição com solvente.