Preparation of the orgamomodified cellulose acetate membranes for adsorption of the ions Cu(II), Cd(II), Mn(II) AND Ni(II)

Cellulose acetate polymeric membranes had been prepared by a procedure of two steps, combining the method of phase inversion and the technique of hydrolysis-deposition. The first step was the preparation of the membrane, and together was organomodified with tetraethylortosilicate and 3-aminopropyltrietoxysilane. Parameters that exert influence in the complexation of the metallic ion, as pH, time of complexation, metal concentration, had been studied in laboratory using tests of metal removal. The membranes had presented resistance mechanics and reactivity to cations, being able to be an alternative for the removal, daily pay-concentration or in the study of the lability of metals complexed

Comparison between ultrasound assisted extraction and microwave digestion in the determination of arsenic in edible grains.

A comparative evaluation of arsenic extraction from grains using ultrasound assisted extraction (UAE) and microwave digestion (MW) was developed. The arsenic determination was carried out using hydride generation coupled to flame atomic absorption spectroscopy (HG-FAAS). The optimal extraction condition indicated for corn was 20% v v-1 of HCl, temperature of 67 ?C and sonication time of 30 min. For bean, the optical condition was HNO3 in a 10% v v-1, temperature of 25 ?C and sonication time of 10 min and for soybean it was 30% v v-1 HCl, temperature of 60 ?C and time of 10 min. Recovery studies close to 100% in the extraction of spiked samples was achieved. The results obtained were compared with two common extraction methods for arsenic using microwave digestion and the developed methods showed a significant increase in the arsenic recovery from the samples. In the real samples it was found an arsenic concentration of 0.3 ?g g-1. The developed methods proved to be efficient at extracting the arsenic present in the studied grains, being appropriate to evaluate the risk to human consumption

Optimization of a homogeneous ternary solvent system for the quantification of lead in crystal sugar samples.

During sugar production, contamination of the sugar by potentially toxic metals may occur. Therefore, it is necessary to develop methods to quantify these contaminants. Analytical method for monitoring of lead in sugar samples was developed with the use of homogeneous ternary system of solvents and UV-Vis spectrophotometry. Ternary system was optimized using multivariate experiments and the best condition was: 10% water, 80% ethanol and 10% methyl isobutyl ketone. As the complexing agent, monosodium 4-(2-pyridylazo) resorcinol used. Calibration curve was linear from 0.64 to 5.00 mg L-1, ABS = 0.0873 [Pb2 +] - 0.0032 and R? = 0.9988. The limit of quantification was 0.53 mg L-1 and limit of detection was 0.45 mg L-1 with 95% confidence level, the standard addition curve was linear, ABS = 0.0736 [Pb2+] + 0.0846 And R? = 0.9971. Three samples were analyzed in triplicate and the concentration of lead obtained ranged from 84.74 ? 3.70 mg kg-1; 69.93 ? 11.84 mg kg-1 and 76.45 ? 7.12 mg kg-1. For the standard addition curve, the concentration found was approximately 230.00 mg kg-1. Considering the Brazilian standard, the lead concentration should not exceed 2.00 mg kg-1, thus, it?s concluded that the values obtained were not within the norm for this metal

Use of Mass Spectrometry for the Determination of Formaldehyde in Samples Potentially Toxic to Humans: A Brief Review

The chemical characteristics of formaldehyde make it widely used and important in the global economy. It has applications in the health area and in various industrial sectors. However, formaldehyde is considered toxic substance and is classifed as a persistent organic pollutant. Direct and prolonged contact with formaldehyde can cause serious damage to the body and may even lead to death. It is classifed by several agencies as a human carcinogen and may exhibit mutagenic/teratogenic efects and/or damage the endocrine system. Various matrices have been found to contain formaldehyde at concentrations higher than those permited by global health regulatory agencies. To this end, mass spectrometry can provide a very useful tool, enabling the identifcation and quantifcation of formaldehyde. Although various analytical techniques can be used for the determination and quantifcation of volatile organic compounds, chromatography is one of the most widely used methods due to its precision. Coupled to a detection system such as mass spectrometry, it can be employed for the determination of compounds potentially toxic to humans, including formaldehyde. The purpose of this chapter is to summarize some recent and important studies concerning the quantifcation of formaldehyde using mass spectrometry as a powerful analytical tool

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) ≈500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) wide-spread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications

Desenvolvimento de métodos analiticos para determinação de 'CD', 'CU','NI'e 'PB' em biodiesel por espectrometria de absorção atômica em forno de grafite

O biodiesel, também conhecido como diesel vegetal, é um combustível obtido de fonte renovável, considerado ambientalmente atraente e uma ótima alternativa em substituição ao diesel. Porém, contaminantes inorgânicos podem estar presentes em amostras de biodiesel devido à absorção de metais pela própria planta (matériaprima) do solo, e/ou podem ser incorporados durante o processo de produção/ transporte/estocagem. Desta forma, por meio de um controle analítico dos teores de contaminantes inorgânicos é possível gerenciar a qualidade dos combustíveis e avaliar o impacto ambiental destes. Este trabalho propõe o desenvolvimento de métodos analíticos para a determinação de Cu, Cd, Ni e Pb em amostras de biodiesel por espectrometria de absorção atômica em forno de grafite (GFAAS). Os procedimentos univariados e multivariados foram aplicados na avaliação das temperaturas ótimas de pirólise e atomização. O planejamento experimental foi usado também como ferramenta para a investigação de dois modificadores químicos (Pd + Mg e W) e dois diferentes procedimentos de preparo das amostras (amostras na forma de microemulsão e amostras digeridas por via úmida em sistema de microondas com radiação focalizada). Considerando que ao usar planejamento fatorial há um melhor entendimento das variáveis e das relações entre elas, os resultados usando o planejamento fatorial foram escolhidos para a determinação dos analitos nas amostras reais de biodiesel. Optou-se por trabalhar com W, pois os as determinações são mais rápidas, há poucos problemas relacionados ao background, durante a deposição do modificador na superfície do atomizador, as impurezas voláteis do modificador podem ser eliminadas, melhorando os limites de detecção, além do W ser um modificador permanente, o que pode aumentar o tempo de vida útil do atomizador. Os procedimentos...Biodiesel, also known as vegetable diesel, is a fuel obtained from a renewable source and an excellent alternative to diesel. However, biodiesel samples may contain inorganic contaminants due to the plant’s (raw material) absorption of metals in the soil, and/or be incorporated during production, transportation or storage. Therefore, based on the analytical control of the inorganic contaminant content, it is possible to manage the quality of fuels and evaluate their environmental impact. This work proposes the development of analytical methods for the determination of Cu, Cd, Ni and Pb in biodiesel samples using graphite furnace atomic absorption spectrometry (GFAAS). Univariate and multivariate procedures were applied in the evaluation of the optimal temperatures of pyrolysis and atomization. Experimental design was also used as a tool in the investigation of two chemical modifiers (Pd + Mg and W) and two different sample preparation procedures (microemulsions and wet digestion in a focused microwave system). Using a factorial design there is better understanding of variables and relations between them and the results using the factorial design were chosen for the determination of analytes in real samples of biodiesel. Therefore, it was decided to work with W, since the heating programs are faster, there are few background problems, the volatile impurities of the modifier can be eliminated during its deposition on the surface of the atomizer, improving the detection limits, and W is a permanent modifier, which may help prolong the service life of the atomizer. The developed analyticals procedures may also be considered satisfactory as were good values of recovery and low standard deviations for all analytes measured in samples of biodiesel. This work contributes to establish or to propose a suitable normalization, since there is not yet in the literature and / or legislation... (Complete abstract click electronic access below)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Desenvolvimento de nanocápsulas de poli-ε-caprolactona contendo o herbicida atrazina

In this study, polymeric nanocapsules of PCL containing the herbicide atrazine were prepared. In order to optimize the preparation conditions, a 2³ factorial design was performed using different formulations of nanocapsules, which investigated the influence of three variables at two levels. The factors varied were the quantities of PCL, Span 60 and Myritol. The results were evaluated considering the size, polydispersity, zeta potential and association rate and the measures of these parameters were taken immediately after preparation and after 30 days of preparation. The formulations with minimum level of polymer in the preparation showed better stability results