Resumo em Inglês:

The concentrations of trace metals Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Zn and V were measured in gills, muscle and hepatopancreas of G. cruentata caught from South of Bahia in order to assess the potential health risk by the consumption of mangrove crabs. The highest metal concentrations in gills, and hepatopancreas were Cu, and Zn in muscles, while the lowest metal concentration in three tissues was Cd and Mo. With the results, it is possible to suggest that the high concentrations of some elements, especially of the Cu, may present risks to the Aratu consumers of the mangrove areas studied, or to other populations where these animals may be transported, same for other cities. The mean concentration of Pb in gills in Una and Jequitinhonha is above the value allowed by the legislation, 3,08 μg g-1 and 3,49 μg g-1, respectively. The concentration of Mn in the females in the three estuaries studied was 1.5 to 4.2 times higher than in the males. In general, detected mean metal concentrations in crab tissues were (in decreasing order) gills > hepatopancreas > muscles. Through the PCA analysis, differentiation between the tissues studied was observed due to its elemental composition. The target hazard quotient (QR) of all trace metals in muscle was less than 1.0 of the provisional tolerable daily intake (IDE) adopted by the USEPA. These results imply that G. cruentata caught from South of Bahia do not have an adverse impact on the consumer health.

Resumo em Inglês:

The goal of the present study was to determine the potential use of thermal analysis for the measurement of the light crude oil (LCO) content of standard biodiesel mixtures. Standard samples of biodiesel/LCO blends were prepared with different ratios of biodiesel; LCO: 1:0 (biodiesel only), 1:3, 1:1, 3:1, 0:1 (LCO only). Thermogravimetry (TG) and differential scanning calorimetry were used to determine the usefulness of thermal analysis for quantification of the LCO in the mixtures. Proton nuclear magnetic resonance (1H NMR) spectroscopy was also used to confirm the composition of the samples. It was found that thermogravimetric curves were not appropriate for the LCO measurements. However, the DSC signal of wax crystallization exhibited a good linear (R2 = 0.99) correlation with the LCO content in the blend. Furthermore, it was shown that aliphatic protons (-CH2-)n in biodiesel and light crude oil can also be used to determine LCO in biodiesel/LCO blends.

Resumo em Inglês:

This study presents the toxicological effects of iron nanoparticles (NP Fe2O3) using in vitro and in vivo tests. Initially nanoparticles were characterized physic-chemically followed by evaluation of cell viability using different cell lines. Allium cepa test and comet assay (cell lines and Danio rerio) were used for evaluation of genotoxicity. Oxidative stress analyses were performed using D. rerio exposed to NP-Fe2O3, and the enzymatic activity of the enzymes catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) were evaluated. The results showed that initially nanoparticles had 65.55 nm, 0.24 of polydispersity of and 11.4 mV of zeta potential. Regarding cell viability, it was observed that this did not reach the IC50 up to the concentration 1 x 1010 NP mL-1. The in vitro comet assay showed that in concentrations 1.96 x108 and 109 NPs mL-1 these presented toxicity, for Allium cepa evaluation in concentrations 19.6 and 39.0 x109 NPs mL-1 presented significant damages when compared to the control. Oxidative stress showed that the liver was the most affected organ when compared to the control. Although studies show that iron nanoparticles do not lead to changes, further studies are needed to make sure they do not lead to environmental changes.

Resumo em Inglês:

There are approximately 300 Myrcia DC. species in Brazil. The antimicrobial, anti-inflammatory and antinociceptive activities of some of these species have been described in the literature. The present study aimed to analyze the chemical composition and evaluate the antinociceptive activity of essential oil from fresh Myrcia rostrata DC. leaves. The oil was obtained by hydrodistillation in a Clevenger-type apparatus and chemical analysis was conducted by GC/FID and GC/MS. The acute oral toxicity and the rota rod tests were executed beforehand. The nociceptive tests (acetic acid-induced writhing, formalin and hot plate) were performed with the oil at doses of 75, 150 or 300 mg kg-1. Of the constituents identified, 95.24% were sesquiterpenes, carotol (17.68%) being the major compound. The essential oil caused no obvious signs of toxicity, nor did it affect the motor coordination of the animals. In conclusion, the animals that received the oil, especially at 300 mg kg-1, demonstrated a lower number of writhes (1.62 versus 27.88±2.75), a decrease in paw-licking time in both phases of the formalin test, and increased latency on the hot plate when compared to the control group.

Resumo em Inglês:

For proper plant growth, soil substrates must be successful for chemical and physical properties in a way that ensures a high capability to reach the nutritional demand of the plant. A suitable nutritional method is the application of organic compounds, urea and, recently, biochar. Here, using the photoacoustic absorption spectroscopy in the visible range, it was analyzed the nutritional capacity of soil samples, submitted to different treatments. This analysis was carried out through the absorption peaks of A and B chlorophylls and cuticle of papaya leaves planted in soils with addition of biochar and with (without) mycorrhiza. All treated samples showed an increase in the peaks of chlorophyll activity in relation to the base sample. Moreover, the samples containing both mycorrhiza and biochar presented the highest peaks of chlorophyll activity, proving to be the best soil fertilization treatment.

Resumo em Inglês:

The kinetics of photoisomerization and thermal back reaction of mercury(II) and zinc(II) dithizonates, M(HDz)2, were analyzed by photolysis assays in fluid solution and in poly(methyl methacrylate), PMMA, films. In fluid solution, the photo- and thermoisomerization of both complexes can be described by a single exponential function. The Zn(II) dithizonate exhibits rate constants three orders of magnitude greater than that for Hg(II) complex, which is attributed to the higher charge density of the Zn(II) cation. In PMMA films, the thermal back reaction of both complexes can only be described by bi-exponential functions. On this more rigid medium the rate constants are about one order of magnitude slower than the respective ones in fluid solution and the bi-exponential behavior is related to regions in the polymeric matrix with distinct free volumes. The rate constants for both photo- and thermoisomerization of Zn(HDz)2 in PMMA are reported for the first time and are compared with the well-studied Hg(II) analog. The experimental data provides insights on the role of the metal cation on the photocromic behavior in rigid media, which can lately contribute for technological applications.

Resumo em Inglês:

The development of films from natural polymers is an alternative to reduce the consumption of packaging obtained from non-renewable sources. The formation of edible films requires a polymeric material that forms a homogeneous and continuous matrix. The gelatin is a natural polymer, cheap and abundant, characteristics that instigate its use. The aim of this study was preparing and characterize gelatin films and evaluate the influence of lemon essential oil nanoemulsion on gelatin matrix for an innovative application of the product. The films were characterized for their water vapor permeability (WVP) test, contact angle, thickness and mechanical analysis (tensile strength and elongation at break). The particle size showed an average of 170.6 nm and zeta potential around -10.9 mV. The incorporation of lemon nanoemulsion increased the water vapor permeability of the gelatin and the elongation, but decreased tensile strength due to the interaction with the hydrophobic portion of the polymer matrix.

Resumo em Inglês:

This work was undertaken in the Velhas River Basin, in the municipalities of Rio Acima, Nova Lima, Raposos and Sabará, upstream of the city of Belo Horizonte in Minas Gerais State, Brazil. Velhas River provides the public water supply for much of this region. The gold and iron mining activities in the Velhas River yield considerable amounts of suspended solids as well as metals to the hydrological system of the region. Thus, the present study sought to evaluate the concentrations of arsenic and trace metals in the waters and their distribution and mobility in sediment by BCR sequential extraction. Arsenic concentrations in the water samples were between 78.1 and 85.3 μg L-1, which exceeded 10 μg L-1 (maximum limit permitted by Brazilian environmental regulations for water destined to human consumption, CONAMA Resolution 357/2005). The sequential extraction of the sediment showed considerable amounts of As (20%), Cd (55%), Co (56%), Cr (16%), Cu (23%), Ni (29%), Pb (47%) and Zn (71%) associated with the geochemical fractions considered potentially available for the remobilization to the aquatic environment. The presence of the elements in these fractions indicated high ecotoxicological risk and potential harm to the health of the local population.

Resumo em Inglês:

The immobilization of horseradish peroxidase (HRP) on raw and alkaline pre-treated sugarcane bagasse by physical adsorption (ADS) and covalent bond (LC) methods was studied. The saturation of the support with 2 mg of HRP/g of support by LC immobilization reached 35% of immobilization efficiency and 39 units of the immobilized enzyme (U). Regarding the HRP immobilization on sugarcane bagasse without pretreatment and using the same HRP loading, it was observed a reduction in the efficiency of immobilization and in the number of immobilized units for both methods, ADS (13.98% and 15.46 U) and LC (15.79% and 17.46 U). The sugarcane bagasse with alkaline pretreatment experiment, on the other hand, exhibited higher potential for HRP immobilization by LC. The supports and biocatalysts were characterized by Fourier transform infrared spectroscopy (FTIR), showing greater availability of hydroxyl groups in the pretreated support and the typical amide I and amide II bands that corroborate the effectiveness of the enzyme immobilization on sugarcane bagasse. In the same way, the thermogravimetric analysis (TGA) confirmed a higher weight loss in the region I for the derivative immobilized by LC, suggesting the presence of water favored enzymatic activity.

Resumo em Inglês:

This work examines the leaching of printed circuit boards (PCBs) from cell phones in aqueous solutions containing HF + H2O2 or HF + NaClO under mild experimental conditions. The PCBs were not ground but were previously treated with 6 mol L-1 NaOH at 50 ºC for 1 h to remove their soldering mask. The HF + H2O2 mixtures leached copper and base metals (except lead) at 35-40 ºC, leaving a solid residue containing lead and noble metals. Leaching was fastest (1 h) when HF and H2O2 concentrations were at least 5 mol L-1 and 3 mol L-1, respectively. The processing of the solid residue is also described in detail. It was leached with water at ~90 ºC followed by HNO3aq. at 25 ºC. Lead, palladium and silver were recovered in this order, leaving gold as final solid. After 1 h at 35-40 ºC, 5 mol L-1 HF + 0.3 mol L-1 NaClO mixtures leached the base metals, copper, gold and palladium. Gold was recovered by liquid-liquid extraction with methyl isobutyl ketone. Silver precipitated as chloride. This salt was isolated by leaching with NH3aq. Loss of fluoride ions (as HF) was below 0.5 wt.% after leaching and handling the solid residue.

Resumo em Inglês:

Nickel complexes have been widely used as catalysts in organic reactions. Their low price compared to Pd and Pt complexes, in addition to their high reactivity and affinity to ϖ systems; the possibility to access different oxidation states and the difficulty to undergo beta-hydride elimination are important features that have attracted the attention of chemists in recent decades. Furthermore, some drawbacks observed with Pd catalysis have been solved by Ni catalysis. These Ni based-catalysts have been used in different reaction manifolds to promote challenging transformations. Herein, recent work using nickel catalysts in different types of reactions, such as carbonylations, carboxylations, C-H activations and dual catalytic systems are described. Critical mechanistic investigations, as well as synthetic applications are also covered.

Resumo em Inglês:

The gold mining in the Madeira River basin is performed by dredges and ferries that extract from the bottom of the river alluvial gold which is amalgamated with mercury (Hg). Throughout the process of gold purification, the Hg can be recovered by retort or crucible distillation. Subsequently, the gold is taken to the city of Porto Velho for commercialization, once more being smelted with blowtorch for jewelry making. This study aims to evaluate the Hg concentration exposed in the atmosphere of gold shops via an atomic absorption spectrophotometer coupled to portable cold steam generation (LUMEX) and to determine the occupational exposure through the analysis of urine samples of gold shops workers. Eleven gold shops and twenty workers were investigated. Some risky situations which may accompany the health of employees, such as poor ventilation, lack of exhaust systems and unhealthy places, have been verified in loco. The results showed atmospheric concentrations of Hg above the limits established by WHO, which is at most 200 ng m-3 in four gold shops. All examined presented total Hg results in the urine below the occupational limit of (50.00 μg L-1).

Resumo em Inglês:

This tutorial intends to show to the readers a step-by-step guide to perform a factorial design in their experiments. The examples used here cover most of doubts and questions related to teaching classes at graduation course. Free computational software was applied, as well as, codes were designed by the authors for the calculations. The complexity of each example is attached to the challenges and decisions that the experimentalist faces in its research. In addition, 24 videos were prepared to help the readers. The authors hope to foster the factorial design as an easy and helpful tool for chemists and general researchers in academia and industry.

Resumo em Inglês:

There are several consequences of the negative or poor perception that society tends to maintain with Chemistry like the lack of interest of students in considering Chemistry as a career or the university dropout rates. Given the importance of museums and science centers to contribute to scientific education and arouse people’s interest in science, this article presents a research carried out with Brazilian science centers and museums to appraise the space of Chemistry in non-formal places of Education. The results obtained are similar to some international data showing the amount of chemistry-related content in museums is insufficient, not exceeding the 40% rate. Most of the activities are aimed at supporting formal education by offering courses for teachers and students through the use of laboratories or conducting experiments when there is available monitoring. Chemistry can be considered in the development of science museums exhibitions and, with the guidance of scientists, it can be shown and discussed without creating distorted visions, sensationalism or conceptual misconceptions.

Resumo em Inglês:

A mathematical model is proposed to investigate the kinetics and equilibrium of homogeneous elementary first- and second-order chemical reactions. The dynamics is defined by the Monte Carlo method (MCM), with the Metropolis update, and the Ehrenfest urn model (EUM). MCM is an important step that accesses the kinetic and thermodynamic properties of the system, while the EUM defines the orders of the reactions studied in this work. The main parameters, such as temperature, the activation energy and the steric factor, were taken into account in the calculation of the transition probabilities between the reactants and products. It is thus possible to reproduce the kinetic profiles of the reactions and to evaluate the influence of temperature and the steric factor. Furthermore, it is possible to simulate the behaviour of the system by modifying the activation energy barrier, thus simulating a catalytic process. The effect of the addition of molecules was also investigated, with the system returning to a thermodynamic equilibrium condition after partial consumption of the added reactant, as predicted by Le Chatelier’s principle. All the simulated data are in agreement with the theoretical results present in physical chemistry textbooks.

Resumo em Inglês:

This work propose the development of an experiment that may be used for the teaching of chemistry for undergraduate students in general, using the analysis of olive oil and soybean oil toward the direct injection electrospray ionization Mass Spectrometry - DI-MS/MS with 18-crown-6 as organic modifier. Firstly, olive oil was analyzed from two different brands, one of reputed brand and the other of popular brand and lower price. Soybean oil of popular brand was also analyzed in order to search possible similarities in the components of these oils and to search adulterations of olive oil with soybean oil. The mass spectra were obtained in positive ion mode of analysis, and allowed us to observe characteristic ions of soybean oil, olive oil, and identify the adulterated olive oil. This simple experiment of easy development may be applied in any institution which has a mass spectrometer with electrospray ionization. In addition, with the use of the experiment, the teacher can illustrate general chemistry concepts such as: molecular mass, preparation of solutions, oxidation, and acid-base reactions.