Ph.D. (Chemistry) / The main objective of this study was to develop sample preparation methods based on separation and preconcentration of trace metals in organic matrices (alcohols, diesel and gasoline). The presence of metals in organic matrices is undesirable, unless they are used as additives. Therefore, it is important to control and monitor their concentrations in fuel and petrochemical products as they tend to affect the quality of these products. Solid phase extraction (SPE), solid phase microextraction (SPME) and hollow fiber-liquid phase microextraction (HF-LPME were used for separation and preconcentration of Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Ti, V and Zn prior to their inductively coupled plasma optical emission/mass spectrometric (ICP OES/-MS) determination. For solid phase extraction, the exchange efficiencies of different commercial ion exchange resins, namely Dowex 50W-x8, Dowex 1-x8, Dowex MAC-3 and Chelex 100, for preconcentration of metal ions in alcohol and fuel samples, were investigated. The results obtained indicated that Dowex 50W-x8 was suitable for simultaneous preconcentration of cations such as Cd, Co, Ni, Cu, Fe, Mn and Zn, among other metals while Dowex 1-x8 was suitable for metal ions that exists in more than one oxidation states, namely, As, Cr, Mo, Sb and V. Chelex-100 and Dowex MAC-3 were found to be selective to a limited number of target metal analytes. For further applications, Dowex 50W-x8 and Dowex 1-x8 were employed. Furthermore, the applicability of synthetic adsorbents such as nanometer-sized alumina and functionalized cellulose nanofibers for preconcentration of trace metals in gasoline samples, was investigated. Nanometer-sized alumina sorbent was found to be suitable for simultaneous separation and preconcentration of Co, Cr, Mn, Ni and Ti. Functionalized cellulose nanofibers on the hand, were suitable for simultaneous preconcentration of Cd, Cu, Fe, Pb and Zn. The optimization of the experimental parameters was achieved by both univariate and multivariate procedure. The second preconcentration technique was solid phase microextraction which was also used for extraction and enrichment of metal ions in diesel samples using two approaches of the SPME method. The first approach was hollow fiber-solid phase microextraction (HF–SPME) method using fiber-supported sol-gel combined with a cation exchange resin (Dowex 50W-x8). This method showed satisfactory results for the preconcentration of Cd, Cu, Fe, Pb and Zn in diesel and gasoline samples. The second approach was based on membrane solid phase microextraction (MSPME) using titania-alumina hollow fiber. The MSPME method applied was used for extraction and preconcentration of trace amounts of Co, Cr, Mo, Ni, Sb and V in liquid fuel samples. Multivariate techniques were used for optimization of experimental parameters for both approaches. The last preconcentration technique that was developed was hollow fiber- liquid phase microextraction (HF-LPME). In this method fuel samples were first digested before being subjected to HF-LPME system. Ammonium pyrrolidine dithiocarbamate (APDC) and [C6MIM][PF6] ionic liquid were both used as chelating agent and acceptor phase, respectively. Two level factorial and central composite designs were used for multivariate optimization of experimental parameters. Satisfactory results were obtained for extraction and preconcentration of Ag, Al, As, Mn and Ti.

Neste trabalho foi desenvolvido um método empregando a microextração líquidolíquido dispersiva em fase reversa (RP-DLLME) para extração e pré-concentração de Al, Cd, Cu, Fe, Mn, Ni e Zn em amostras de óleo diesel. A determinação dos analitos foi feita por espectrometria de emissão óptica de plasma indutivamente acoplado (ICP-OES). Para a etapa de extração e pré-concentração, empregou-se uma mistura de solventes dispersor e extrator, a qual foi adicionada diretamente na amostra aquecida. Posteriormente, para separação das fases, as soluções foram centrifugadas e, foi retirada a fase sedimentada para determinação dos analitos por ICP-OES. Para o desenvolvimento do método foi utilizado o planejamento experimental e otimização de processos, onde inicialmente utilizou-se um planejamento fatorial fracionado e em seguida um delineamento composto central rotacional. As variáveis estudadas foram temperatura de extração (60, 70 e 80 oC), massa de amostra (5, 10 e 15 g), volume da solução extratora (0,5, 1 e 1,5 mL), concentração do extrator (1, 1,5 e 2 mol L-1) e proporção do dispersor na solução extratora (60, 70 e 80%). Resultados quantitativos foram obtidos empregando as seguintes condições: i) temperatura de extração: 70 oC, ii) massa de amostra: 8,5 g, iii) volume da solução extratora: 1 mL, iv) concentração de HNO3: 2 mol L-1 e v) proporção do dispersor: 70% (v/v). Todos os experimentos foram feitos usando a adição de 1,0 µg g-1 de Al, Cd, Cu, Fe, Mn, Ni e Zn diretamente nas amostras de diesel, para isso foi utilizado um padrão multielementar de óleo lubrificante Conostan® (100 mg L-1). Os resultados foram expressos como recuperação dos analitos (%). As soluções de calibração foram feitas em solução aquosa e os extratos foram diretamente determinados por ICP-OES. Os limites de quantificação (LQ) para Al, Cd, Cu, Fe, Mn, Ni e Zn foram 0,0492, 0,0031, 0,0031, 0,0140, 0,0008, 0,0049 e 0,0093 µg g-1, respectivamente. A exatidão do método foi avaliada por meio de ensaios com adição de analitos. Recuperações quantitativas foram obtidas para todos analitos e os desvios padrão relativos foram inferiores a 7%. Posteriormente, o método foi aplicado para 6 amostras de óleo diesel comercial, S-10 e S-500, e a concentração de Al, Fe e Zn foi na faixa de 0,026 até 0,150 µg g-1, os demais analitos ficaram abaixo do LQ do método. Então, o método desenvolvido empregando a RP-DLLME e posterior determinação por ICP-OES apresentou-se com precisão e exatidão adequados para determinação de Al, Cd, Cu, Fe, Mn, Ni, Zn em óleo diesel em baixas concentrações, minimizando o consumo de reagentes e, consequentemente a geração de resíduos, de forma rápida e de simples execução, mostrando-se adequado para análises de rotina. / This research developed a method for employing a reversed-phase dispersive liquidliquid microextraction (RP-DLLME) as sample preparation for the extraction and preconcentration of Al, Cd, Cu, Fe, Mn, Ni and Zn in biodiesel samples. The determination of analytes were executed through inductively coupled plasma optical emission spectrometry (ICP-OES). The extraction/pre-concentration step of the analytes was performed using a mixture of two solvents, a dispersing and an extractor, which were added directly to the heated sample. Subsequently, for separation of the phases, the solutions were centrifuged and the sedimented phase was withdrawn to determine the analytes by ICP-OES. For the development of the method was used the experimental planning and optimization of processes, where initially a fractional factorial design was used and then a central composite rotatable design. The variables studied were temperature of the extraction (60, 70 and 80 oC), sample mass (5, 10 and 15 g), volume of extraction phase (0.5, 1 and 1.5 mL), concentration of the extraction (1.5 and 2 mol L-1) and the proportion of the dispersant in the extractive solution (60, 70 and 80%). Quantitative results were obtained using the following conditions: i) temperature of the extraction: 70 oC, ii) sample mass: 8.5 g, iii) volume of extraction phase: 1 mL, iv) concentration of HNO3: 2 mol L-1, and v) proportion of dispersant: 70% (v / v). All experiments were performed using the addition of 1.0 μg g-1 of Al, Cd, Cu, Fe, Mn, Ni and Zn directly in the diesel samples, was used a standard multi-element Conostan® lubricant oil (100 mg L-1). The results were expressed as analyte recovery (%). The calibration solutions were made in aqueous solution and the extracts were directly determined by ICP-OES. The quantification limits (LQ) for Al, Cd, Cu, Fe, Mn, Ni and Zn were 0.0492, 0.0031, 0.0031, 0.0140, 0.0008, 0.0049 and 0.0093 μg g-1, respectively. Accuracy was assessed by addition of analytes. Quantitative recoveries were obtained for all analytes and the relative standard deviations were less than 6.4%. The method was applied to 6 samples of commercial diesel oil, S-10 and S-500, and Al, Fe and Zn were determined in the range of 0.026 to 0.150 μg g-1, the remaining analytes were below the LQ of the method. The method developed using RP-DLLME and determination by ICP-OES presented with adequate precision and accuracy for the determination of Al, Cd, Cu, Fe, Mn, Ni, Zn in diesel oil in low concentrations, minimizing reagent consumption and, consequently the generation of toxic wastes, in a fast and simple way, and is suitable for routine analysis.