Resumo em Inglês:

Electrochemical methods are an interesting and clean alternative for the abatement of toxic organic pollutants. This paper details the study of the synthesis of electrode materials of nominal composition Ti/PbXTi1-XO2 (X = 0; 0.05; 0.10; 0.20 e 0.30) and their use as electrodes for degradation of organic pollutants using both electrochemical and photo-assisted electrochemical techniques. The results demonstrate that the materials produced are interesting from the point of view of organic removal. The application of simultaneous UV radiation with electrical current was capable of removing greater amounts of the organic load (>32% in <1 h) than the electrochemical technique alone.

Resumo em Inglês:

A few years ago, during a storage room clean out at the University of São Paulo (Biblioteca do Conjunto das Químicas), several items were discarded, including apparently modern worthless large-scale reproductions of paintings by famous painters. A member of staff retrieved these reproductions from the litter bin, one of which was carefully inspected and non-destructively analyzed by spectroscopic techniques (Raman and XRF). The results showed that instead of being a modern reproduction of the gouache "Clinique de Sannois" (Maurice Utrillo, 1923), it was hand-painted probably between the late 1940s and early 1950s using the Jacomet process. This technique was developed by the French printer Daniel Jacomet in the 1920s, who made authorized reproductions of works of art by some of the most celebrated painters of the time.

Resumo em Inglês:

MCM-41 structures were synthesized and modified by direct (one-step) incorporation (DI) and wet impregnation (WI) methods. The solids were characterized by XRF, XRD, N2 adsorption and UV-Vis DR, and catalytically evaluated in the Acid Orange 7 (AO7) degradation under visible light. Significant influence of the presence, dispersion and location of the different Cr species on photoactivity was evident. Both synthesis methods allowed greater dispersion of the photoactive Cr species for lower metal content, enhancing efficiency for dye degradation. More specifically, after Ti loading in samples synthesized by DI, a notable AO7 degradation increase was associated with the strong heterojunction between Ti and Cr6+ species, which wereare highly dispersed due to the DI method used.

Resumo em Inglês:

Six new salts of organometallic complexes of tin(IV) with the general formulae: (Ph4P)2[Sn(Bu)2(RSO2N=CS2)2] and [Fe(phen)3][Sn(Bu)2(RSO2N=CS2)2] [Ph4P = tetraphenylphosphonium, R = CH3 (1), C2H5 (2) and C4H9 (3); Fe(phen)3 = tris(1,10-phenanthroline)iron(II), R = CH3 (4), C2H5 (5) and C4H9 (6)] were synthetized from potassium dithiocarbimates (RSO2N=CS2K2.H2O) in reaction with dichlorobis-n-butyltin(IV) and tetraphenylphosphonium chloride (1-3) in N,N-dimethylformamide or tris(1,10-phenanthroline)iron(II) (4-6) in methanol. The new compounds were characterized by elemental analysis of Fe and Sn, and by vibrational, Mössbauer and nuclear magnetic resonance of 1H, 13C and 119Sn spectroscopies. High-resolution mass spectra in the negative and positive modes were also obtained. The elemental analyses and the exact masses obtained for the cations and the complex anions were consistent with the proposed formulae. The Mössbauer spectroscopic data were consistent with the presence of tin(IV) with coordination numbers between 4 and 5 (compounds 1-6), and of hexacoordinated iron(II) (compounds 4-6). The 1H and 13C NMR spectra presented all the expected signals for the cations and anions, and the signals observed in the 119Sn NMR spectra indicated an equilibrium between tetra- and pentacoordination around the tin atoms in solution. The in vitro activity of the new compounds was evaluated against Botrytis cinerea and Colletotrichum acutatum.

Resumo em Inglês:

Cadmium is considered a potentially toxic element, since it doesn't perform any biological function and is highly cumulative. This element is usually found in environmental samples in very low concentrations. For this reason, there is a necessity to develop methods that allow sufficiently low detection limits. From this perspective, a simple, sensitive, selective and low cost methodology was developed for the determination of Cd by F AAS. The system involves the on-line pre concentration of cadmium onto a commercial polystyrene divinil benzene (PSDV) resin modified with phenylfluorone (PF). The experimental conditions (both chemical and physical) were optimized to achieve highest sensitivity. The modified resin had high chemical and physical resistance, and could be reused for 300 cycles without compromising the system's sensitivity. The obtained enrichment factor was around 8 times and accuracy, calculated as relative standard deviation (RSD), of 5.5% for cadmium concentration of 40 µg L-1. The limits of detection and quantification obtained were 0.15 and 0.49 µg L-1, respectively. This methodology proved to be applicable for samples of river waters, in which matrix interferences were not observed. In these samples recovery tests were conducted in order to evaluate the accuracy of the method, and these results varied between 89 and 118%.

Resumo em Inglês:

The aim of this study was develop in silico studies with a data set of 1 H -imidazol-2-yl-pyrimidine-4,6-diamines derivatives described as antimalarial agents with the intention of obtain data and tools useful in the development of new drugs of this class. A QSAR model was developed using topological, geometrical and electronic molecular descriptors with aid of the OPS/PLS approach. The data set was also used for pharmacophoric modeling, that was used in the ZINC database for found compounds that show good fit with the model. Due to the similarity between the four selected hits in the virtual screening with the data set, the obtained equation was used for predict the potential antimalarial activity. All hits were within the applicablity domain of the QSAR model, and showed adquates Monge's leadlikeness score and predicted safety profiles.

Resumo em Inglês:

The Wilkinson complex was tested as a catalyst in the partial hydrogenation of 1-heptyne, a medium chain alkyne, at a temperature of T = 303 K and hydrogen pressure PH2 = 150 kPa. The tests were performed in homogeneous system as well as heterogeneous system, supporting the complex on i) γ-Al2O3 and ii) a commercial carbonaceous material, RX3. Characterization by means of XPS and FTIR revealed that the anchored complex did not lose its chemical identity, being the catalytically active species. The Wilkinson complex on RX3 showed better conversions and selectivities, higher than the Lindlar catalyst, used as a reference. Additionally, it was proposed a method to recover Rh as a metal from the remaining solutions, and from it regenerate the complex to be reused from it.

Resumo em Inglês:

The medicinal plants Panax ginseng C. A. Meyer (Araliaceae) and Heteropterys tomentosa A. Juss (Malpighiaceae) are widely and separately used by the Brazilian population as phytotherapeutics for the same medicinal purposes as tonics and to improve cognition. A chemical analysis was carried out on hydroethanolic extracts of powdered roots from P. ginseng and H. tomentosa using HPLC-DAD-ESI-MS/MS (High Performance Liquid Chromatography coupled to Diode-Array Detector and Electrospray Ionization - Mass Spectrum/Mass Spectrum). The ginsenosides Rg1, Rf, mRg and mRf were the main constituents in a hydroethanolic extract from P. ginseng, while in the hydroethanolic extract from H. tomentosa, caffeoylquinic acid derivatives and astilbin isomers were the main constituents. Concentration-time-effect curves were generated in cultures of astrocytes that were incubated with hydroethanolic extracts of these species to elucidate their toxicities. The P. ginseng extract was nontoxic at all of the tested times and concentrations. The hydroethanolic extract from H. tomentosa demonstrated toxicity at a concentration of 1000 µg/mL. P. ginseng extract had no protective effect against staurosporine. Many studies have demonstrated the neuroprotective effect of ginsenosides, caffeoylquinic derivatives and flavonoids.

Resumo em Inglês:

Densities of DL-alanine in aqueous ionic liquid, 1-butyl, 3-methylimidazolium tetrafluoroborate solutions were measured from 283.15 to 313.15 K. The densities measured were used to calculate apparent molar volumes (VΦ), apparent molar volume limits (VΦ0), transfer molar volume limits (ΔVΦ0) and hydration number (NH). The behavior of (ΔVΦ0) was interpreted in terms of solute-solvent interactions on the basis of the cosphere overlap model. The hydration numbers were positive and explained by dehydration and electrostriction.

Resumo em Inglês:

This paper describes a procedure based on multicommutation in flow analysis system for photometric determination of hydroquinone in pharmaceutical gel formulations. The procedure involves oxidation of hydroquinone by Fe (III) and subsequent reaction between the generated Fe (II) species with 1,10-phenanthroline, producing a complex detected at 510 nm. Under optimized conditions, the proposed system showed a linear response in the range between 5 to 120 µmol L-1 (r = 0.9995), a limit of detection (3σ) 0.52 µmol L-1 and a relative standard deviation (RSD) of 1.5% for a 80 µmol L-1 hydroquinone standard solution. Others profitable features such as an analytical frequency of 72 samples per hour; a reagent consumption of 0.432 and 0.117 mg 1-10-phenantroline and FeCl3.6H2O per determination, respectively; and a waste generation of 4.0 ml per determination were also achieved.

Resumo em Inglês:

In recent decades, the occurrence of pharmaceuticals in the environment has been widely reported due to their high frequency and recalcitrance in many cases. Concerning the chiral pharmaceuticals (CPs) in environmental matrices, the stereochemistry is often neglected and enantiomers are determined together as unique molecules. However, it is well known that CPs might have enantioselective toxicity, rendering important to assess the occurrence and degradation processes of single enantiomers in the environment, namely during biological treatment in wastewater treatment plants (WWTPs). The development of analytical methods to qualitatively and quantitatively evaluate the enantiomers of CPs is crucial for determining enantiomeric fraction (EF). The EF is the most important parameter in studies involving enantiomers and enantioselective processes and fundamental in biodegradation studies and wastewater monitoring. This review summarizes the analytical methods used to determine EF of CPs in environmental matrices and/or during biodegradation processes. The occurrence of CPs in the environment and their biodegradation are reviewed and future trends in the area outlined.

Resumo em Inglês:

Advanced glycation (AGEs) and lipoxidation (ALEs) products are formed through specific condensation reactions between nucleophiles (amino groups of free amino acids or their residues in peptides, aminophospholipids or proteins) and electrophiles (carbonyls of reducing sugars, oxidized lipids or others) generating well-defined sets of covalent adducts. The ε-amino group of the lysine is the most reactive precursor in proteins and the primary target of carbohydrate attacks. AGEs/ALEs accumulation has consequences in the development of vascular, renal, neural and ocular complications, as well as in the triggering of inflammatory and neurodegenerative diseases. Therefore, AGEs/ALEs detection, quantification and, in some cases, the assessment of the extent of glycation in biomolecules of different matrices represent a factor of primary interest for science. Reliable analytical methods are thus required. Together with basic concepts, this review presents the main advances, challenges and prospects of research involving AGEs and ALEs in biological and food systems, exploring practical strategies to ensure greater reliability in the analysis of these compounds in different matrices.

Resumo em Inglês:

Pequi (Caryocar brasiliense Camb.), a typical fruit of the Brazilian Cerrado, is an important source of micronutrients and fatty acids. In this work, a new approach for the acid digestion (using H2SO4, HNO3 and H2O2) of pequi oil samples and the determination of Cu, Fe, Zn and Mn by flame atomic absorption spectrometry (F AAS) was employed. Capillary zone electrophoresis (CZE) was used for free fatty acid (FFA) determination after simple and fast extraction with heated ethanol. Good results regarding precision (RSD < 10%, in most cases), sensitivity and adequate LOD and LOQ values were obtained. The accuracy was evaluated using spike tests and the recoveries were from 97 to 107%. The analytes were investigated in four different pequi oil samples. Fe was the trace element with the highest concentration (from 1.99 to 10.3 mg/100 g), followed by Zn, Mn and Cu (1.15 to 3.19, 0.42 to 0.91 and 0.31 to 0.56 mg/100 g, respectively). The main FFA found were oleic acid and palmitic acid (1.61 to 10.7 and 0.82 to 2.69 g/100 g, respectively), while linoleic acid (0.50 g/100 g) was detected in only one sample. The pequi oil chemical composition showed good characteristics to be used as a food additive, in cosmetic formulations and for traditional medicine.

Resumo em Inglês:

Although the gas-liquid reactions are employed in many industrial processes, this issue in the most of time is not included in the curriculum of Chemistry and Chemical Engineering courses. This work aims to propose the study of gas-liquid reaction for the degree course, considering a widespread system, the reaction of CO2-NaOH. A reaction mechanism was proposed considering all the intermediate reactions. For each point collected in the outlet solution all the products formed were quantified included residual absorbing solutions. The pH of the outlet solution received a special attention, because with this information was possible to study the controversy that there is in the state of art between some authors in consider the product of the reaction bicarbonate when under conditions of high temperature of or long exposure time of the liquid to gas. For this study was used a continuous stirred-tank reactor in which the gas phase simulate a bubble with a defined size in contact with the liquid phase. The experimental were made by trails under atmospheric pressure, using a feed mixture containing 76% to 69% of CO2 and 24% to 31% of synthetic air and as liquid solution sodium hydroxide 0.015 mol L-1, 0.08 mol L-1, 0.56 mol L-1 and 2.0 mol L-1. The experimental results obtained and the behavior of CO2-NaOH reaction were compared with the data reported in the literature and show a good performance.

Resumo em Inglês:

In the last years, higher education teacher training has received more didactic-pedagogical attention. Despite numerous criticisms to professors' work, some practices present differentials that make them a reference to students, even among university professors with undergraduate and graduate degrees in their specific areas of knowledge. To analyze the classes of such professors who become a reference to students, we selected two higher education professors of chemistry and videotaped their classes seeking to identify the teaching strategies that they use. After analysis, we shared the results with the subjects and complemented them with a semi-structured interview. We found out that these professors perform based on counter-models of professors who they had had in their undergraduate courses and developed strategies aiming to minimize for their students the difficulties they themselves had experienced.

Resumo em Inglês:

Cubic equations of state are able to predict the liquid-vapour coexistence curve of volatile substances. However, this property is rarely used to teach Physical Chemistry because solving the resulting equations require numerical technics and many mathematical operations. In this report was shown how the interactive method for finding the root of an equation can be applied with the Excel to determine the vapour pressure of the liquid, as well as the molar volumes of the gas and liquid phases. The generated points was used to build the curves of phase transition in the P ´ V and P ´ T graphics.