No abstract

No presente trabalho foi investigado o desenvolvimento de um método espectrofotométrico limpo para a determinação de formaldeído em amostras comerciais. A substituição de reagentes altamente perigosos foi explorada, de modo a atender aos princípios estabelecidos pela química verde. O método proposto baseou-se na reação entre formaldeído e ácido cromotrópico na presença de sulfato de magnésio, produzindo um complexo estável Mg 2+ /ciclotetracromotropileno (λ max = 535 nm). Não há relatos na literatura sobre a utilização da reação supramencionada na determinação de formaldeído. As condições experimentais foram otimizadas, aplicando-se a metodologia de superfície de resposta. A lei de Lambert-Beer é obedecida na faixa de concentração de 3 a 11 mg L -1 de formaldeído, com coeficiente de correlação de 0,999. O método proposto para a determinação de formaldeído foi aplicado em amostras comerciais de desinfetantes e defrizantes capilares. Os resultados compararam-se favoravelmente aos obtidos pelo método oficial, demonstrando exatidão e precisão satisfatórias.A green spectrophotometric analytical method for determination of formaldehyde in commercial samples was designed and investigated. Replacement of hazardous reagents was explored to attain the clean chemistry standards. The method is based on formaldehyde reaction with chromotropic acid in the presence of magnesium sulphate producing a stable complex Mg 2+ / cyclotetrachromotropylene (λ max = 535 nm). To the best of our knowledge, there are no reports on the use of the above mentioned reaction for this determination. The experimental conditions were optimized by the response surface methodologies. Beer's Law is obeyed in a concentration range of 3 to 11 mg L -1 of formaldehyde with a correlation coefficient of 0.999. The proposed method was applied for the determination of formaldehyde in commercial disinfectants and deffrizing hair products. The results were favorably compared with those of the official method, with good accuracy and precision.

EN 14103 is suitable to quantify the ester content in biodiesel free of heptadecanoate ester (C17:0), because it is employed as internal standard (IS). But EN 14103 cannot be applied to the analysis of tallow biodiesel because C17:0 is found in animal fats. This work proposes an improved method, based on EN 14103 capable to determine ester content in tallow biodiesel. Twenty samples from tallow, soybean, babassu and palm biodiesels and its blends were used to carry out the analysis. Chromatograms of ethylic biodiesel were analyzed using separately methylic and ethylic C17:0 (IS). The results showed that some peaks from tallow biodiesel coeluted with both IS peaks, confirming the impossibility to quantify ethylic esters using those standards. Despite this, in all analyzed samples it was observed a constant relationship between two neighbor peaks occurring naturally in the tallow samples. The rate between them was measured and applied as a correction factor to measure the real influence, caused on methylic C17:0 IS by natural C17:0. As a result, the original equation from EN 14103, modified by the introduction of a correction factor (F), resulted in another equation more adequate to analyze the ester content in tallow biodiesel and its blends. Pure tallow biodiesel presented ester content around 4.3% greater, when quantified using the equation containing the correction factor, instead of the original equation.

Indian-nut (Aleurites moluccana) and tucum (Astrocaryum vulgare) are oleaginous non eatable that present excellent oil content (about 60% and 30%, respectively) compared to soy bean grains (20%). Biodiesel production from these oils, using bioethanol as reactant, is an alternative for renewable energy source. In this paper, experimental design was used to determine the influence of these different kinds of oils on the transesterification reaction in order to evaluate the viability of biodiesel production process using ethanol as reactant. The most influential variables on the transesterification reaction yield were: alcohol to oil molar ratio, mass of catalyst, temperature and reaction time. In this paper, the variables was operated using experimental design with central composite. Compositional difference between both tucum and Aleurites oil has been verified by 1 H-NMR and GC analysis. Physicochemical properties presented by Aleurites biodiesel are in accordance with ANP Regulation n. 07. On the other hand, the same conditions were not adequate to achieve a high transesterification yield from handmade Astrocaryum oil. In this case, better conditions were only obtained from refined oil. The reactional conditions optimized based on a kind of oil sometimes can't be suitable for any biodiesel production reaction.