Resumo em Inglês:

An efficient and non-expensive method for conversion of diverse potassium organotrifluoroborates to their corresponding boronic acids promoted by montmorillonite K10 using water as the reaction solvent is described. Further interconversion of potassium organotrifluoroborates to their corresponding boronic esters, via boronic acid intermediates was also successfully accomplished. The products were obtained in good yields, being the rate of hydrolysis influenced by the type of substituent present in the boronic acid.

Resumo em Inglês:

The interaction between HSA and two semi-synthetic potential anti-cancer agents derived from trans -dehydrocrotonin-methyl-hydrazone (MHDCTN) and phenyl-hydrazone (PHDCTN) was evaluated under physiological conditions at 296, 303 and 310 K by multi-spectroscopic techniques and molecular docking calculations. Steady state fluorescence quenching indicated a ground state association (static quenching) for both samples; however, the quenching induced by PHDCTN was not essentially static and can be accompanied by a dynamic quenching mechanism. The binding is strong (modified Stern-Volmer binding constant (Ka) ca. 105 M-1), causing a very weak perturbation on the secondary structure of the protein and there is just one main binding site for both samples (Sudlow’s site I). Molecular docking results suggested hydrogen bonding and hydrophobic interactions as the main binding forces for both samples.

Resumo em Inglês:

This work presents a simple and fast method for colchicine (CO) determination in pharmaceutical formulations and urine by multiple pulse amperometry (MPA) with flow injection analysis (FIA) system using a boron-doped diamond electrode. In optimized conditions, it was possible to quantify CO in urine samples without interference of uric acid and ascorbic acid. The working linear range for CO quantification was achieved from 1.0 × 10-7 to 0.5 × 10-3mol L-1 with a low limit of detection of 2.14 × 10-8mol L-1. Furthermore, the proposed method showed high repeatability for 10 consecutive injections of 1.0 × 10-4mol L-1 CO (relative standard deviation = 1.28%) and good analytical frequency (30 determinations per hour). The addition and recovery studies in all pharmaceutical samples were approximately 100% and the results for CO determination were compared by high performance liquid chromatography (HPLC) with UV detection.

Resumo em Inglês:

Superduplex stainless steels (SSS) composed in both equal fraction ferritic-austenite phases, classically defined by ASTM A995M Gr.5A, in order to obtain a better relation of mechanical properties and corrosion properties, are applied as components for use in petrochemical industries in off-shore platforms. The corrosion resistance of stainless steels is due to the oxides formed on the surface, which is dependent on the temperature and environment in which they are exposed. This paper investigates a microstructure duplex during steps of thermal attack under vacuum at high temperatures through observation of the coloration and growth of oxide films. Some coloration was observed in the phases, austenite and ferrite, with the increase of the temperature to 1100 ºC, which is indicative of the presence of chromium and iron oxides. In the cooling occurs the stability of oxides present in the films. Electrochemical tests were conducted in H2S/CO2-saturated in two different concentrations of chloride sodium electrolyte, simulating a seawater environment. Potentiodynamic polarization curves indicate that pitting corrosion resistance and repassivation process in media of 3.5 and 9.0% (wt.%) NaCl are not affected by the presence of H2S/CO2 (40/60 ppm) at room temperature (25 ºC).

Resumo em Inglês:

This study shows that polymer nanogels (well-defined cross-linked nanoparticles behaving as highly hydrated unimolecular objects) are suitable capping agents for palladium nanoparticle catalyst systems. In spite of the structurally complex nature of the catalysts, it was possible to go from acrylate-based monomers to ready-to-use and recyclable catalysts in only two-steps. First, nanogels were synthesized by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) method with sequential addition of monomers. Then, in the second step, palladium acetate was reduced to obtain ready-to-use catalysts (ca. 25 nm nanogel structures containing ca. 7 nm palladium nanoparticles). The catalytic activity was confirmed in p -nitrophenol (Nip) reduction and Suzuki cross-coupling reactions. The observed rate constants (kobs) for Nip reduction were in the range of 0.8-10.0 × 10-2 s-1 depending on the polymeric capping agent structure, with the highest value being found for nanogel-based systems. These composite catalysts also mediated the cross-coupling Suzuki reaction providing the expected products in quantitative yields under relatively mild conditions after 4 h at 50 ºC. The simplicity of catalyst preparation protocol that ensures excellent activity and the low concentration of polymer applied during the synthesis are a step forward in terms of environmental and economic prospects.

Resumo em Inglês:

Solid state reaction of serpentinite Mg3Si2O5(OH)4 with NaOH was investigated to produce new NaMgSi oxide phases with basic properties for application in catalysis. X-ray powder diffraction (XRD) showed that NaOH impregnated on serpentinite, specially 20% sodium and treated at 700 ºC (20Na700), led to the formation of a new crystalline phase Na2Mg2Si2O7. This solid state reaction is discussed in terms of a first step involving Na+ diffusion and intercalation in the interlayer space of the serpentinite structure followed by a dihydroxylation and formation of the NaMgSi oxides. Temperature programmed reaction and desorption experiments with 20Na700 combined with XRD suggested a strong basicity with high CO2 uptake likely due to diffusion and interaction with the basic sites in the material structure. These materials were tested as catalysts for the transesterification of soybean oil with methanol. The obtained results are discussed in terms of a basic site Si-O-Na+ present in the in the Na2Mg2Si2O7 structure.

Resumo em Inglês:

The quality control of pellets homogeneity cannot be assessed by conventional techniques and near infrared-chemical imaging combined with multivariate curve resolution with alternating least squares is an attractive alternative. In this study, composition and spatial distribution of pellets components were determined after assessment of experimental parameters. The use of a 25 μm intermediate pixel size, an initial estimation matrix with instrumental signals for pure substances and individual matrices provided a model with explained variance of more than 99% and a value of 0.00263 for percentage of lack of fit. In addition, the similarity between the pure substances spectra and those recovered by the model were 0.9501 for sucrose, 0.9480 for starch, 0.9910 for ketoprofen and 0.5941 for SiO2. Chemical images were generated and show that the pellet is composed of an inert nucleus of starch and cellulose, surrounded by a ketoprofen layer. All this information was obtained quickly, in minutes, being an excellent alternative for pellets analysis.

Resumo em Inglês:

The humic acid (HA) obtained with the activity of three bacterial strains that transformed a lignite-type low rank coal (LRC) and released humified organic matter (HOM) was characterized. The HA obtained with the activity of Bacillus mycoides, Microbacterium sp. and Acinetobacter baumannii were compared with HA obtained with the traditional alkaline extraction method using NaOH 0.5 M (HA-NaOH). These characterizations included the elemental composition (C, H, N, O), Fourier transform infrared (FTIR) analysis, cross polarization-magic angle spinning-nuclear magnetic resonance (13C-CPMAS-NMR), tetramethylammonium hydroxide (TMAH)-thermochemolysis followed by gas chromatography-mass spectrometry (GC-MS) and size exclusion chromatography. The two evaluated HA types showed differences in the elemental composition, aromaticity degree, content of aliphatic groups, molecular weight, polydispersity, profile of the spectra 13C-CPMAS-NMR and products of TMAH-thermochemolysis. The results indicate that the process of biotransformation of LRC with bacterial activity results in the structural transformations of HA, which leads to the formation of HA with a lower degree of aromaticity, more of a hydrophilic tendency, lower oxygen content, enriched with nitrogenated functional groups and polar aliphatic chains, as compared with HA-NaOH. The HA generated with the three bacterial strains exhibited a high structural similarity to each other; however, some differences were evident in the type of metabolites generated by the TMAH-thermochemolysis of the HA obtained with B. mycoides, as well as a higher polydispersity for the HA generated with A. baumannii.

Resumo em Inglês:

Selected emerging contaminants in water samples from the Brazilian capital were investigated by liquid chromatography-mass spectrometry after solid-phase extraction. In Paranoá Lake, an urban reservoir that will be used to produce drinking water, caffeine was the most abundant contaminant found (average of 53 ng L-1), followed by atenolol (34 ng L-1), N, N -diethyl-meta -toluamide (DEET, 12 ng L-1) and atrazine (3.8 ng L-1). The role of wastewaters discharges could not be evidenced probably due to the water flow and circulation in the lake. However, higher concentrations were detected during the dry season suggesting the presence of point sources, except for atrazine. In source waters, concentrations were lower in comparison with Paranoá Lake waters. Environmental risk assessment shows the need for further surveys for atrazine. For drinking waters, only caffeine and atrazine were detected at average concentrations of 8.6 and 3.2 ng L-1, respectively. No risk for human health was observed.

Resumo em Inglês:

Heat map and hierarchical cluster analysis showed that sparkling wines produced with immobilized yeasts contained mostly higher levels of compounds that impart positive notes to wines. Fisher ratio pointed out nine volatile compounds as the main components responsible for differentiation of samples treated with mannoproteins/lees and others. Principal component analysis (PCA) showed differences between the sparkling wines produced with and without adjuvants (commercial mannoproteins or lees). Sparkling wines aged without adjuvants presented higher levels of decanoic and dodecanoic acids (fatty/metallic aroma), while the use of mannoproteins or lees resulted in higher content of some fruity esters, nerolidol and β-damascenone. Therefore, the combination of immobilized yeast and aging on mannoproteins or lees seems to be the most promising treatment to obtain the volatile profile that positively influence wine quality.

Resumo em Inglês:

The immobilization of Burkholderia cepacia lipase (BCL) on pristine or functionalized multi-walled carbon nanotubes (MWCNTs) was studied in the resolution of (RS)-1-phenylethanol. For the functionalization, three treatments were used, these being in H2SO4/HNO3 (acid, MWCNTs-A), KOH (basic, MWCNTs-B) or in H2O2 (oxidizing agent, MWCNTs-O). It was found that the pristine or functionalized BCL/MWCNTs resulted in a 3-fold improvement in the conversion and in a 5-fold improvement in ees (enantiomeric excess of the substrate), when compared with free BCL under the same reaction conditions. This pristine or functionalized BCL/MWCNTs system could be reused for up to 8 times without significant decrease in the catalytic efficiency. Under the optimum conditions (pH of immobilization 6.0, 45 ºC and 25 mg/5 mg pristine or functionalized BCL/MWCNTs), the best results were obtained using BCL immobilized on MWCNTs-A. The simple process of physical adsorption of BCL onto MWCNTs-A has improved the catalytic efficiency when compared with free BCL and an increase in the stability was confirmed by thermogravimetric analysis (TGA).

Resumo em Inglês:

In this scientific work, it was developed a single analytical procedure for the sample preparation of different tissues of blue crabs using microwave-assisted digestion for the determination of Cu, Mn, Fe and Zn by fast sequential flame atomic absorption spectrometry (FS FAAS). The limits of quatification were 10.5, 1.6, 8.9 and 19.3 µg g-1 for Cu, Mn, Fe and Zn, respectively. The precision was estimated in terms of repeatability using the relative standard deviation (RSD, n = 7) 3.4% for Cu; 4.8% (Mn); 4.7% (Fe) and 4.7% (Zn) and accuracy of the procedure was confirmed by analysis of certified reference material (CRM) of oyster tissue (NIST 1566B) with concentration values of 71.3 for Cu, 18.3 for Mn, 202.5 for Fe and 1415 µg g-1 for Zn. The procedure has been applied for the determination of Cu, Mn, Fe and Zn in several blue crab samples from Cachoeira River estuary, Ilhéus, Bahia, Brazil.

Resumo em Inglês:

This paper reports an optimized, simple, fast and inexpensive method for hydroxyapatite (HA) nanoparticle synthesis. Through a multivariate statistical analysis using a factorial design with 23 resolution, an empirical model was developed which allows control of the shape and size of the HA nanoparticles. This model was used to synthesize HA nanoparticles with sizes between 8 and 600 nm, formed by oriented attachment growth mechanism. The structure was confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images, which also showed that HA nanoparticles had well-defined nanorod forms and narrow size distributions. It was observed that the model is statistically significant and the main parameter for the growth of crystals in the hydrothermal process was temperature.

Resumo em Inglês:

Porous carbon materials were prepared at low temperatures via thermal decomposition of iron, nickel and cobalt N, N -diethyldithiocarbamates (DDT). X-ray diffraction data showed two peaks at 2θ (25.5º and 43.5º) that indicate the presence of graphite-like structures. Raman spectra displayed D and G bands in the range from 1312 to 1321 cm-1 and 1587 to 1593 cm-1, respectively, which were fitted with 4 components. All spectra showed two low intensity D* (1190 cm-1) and D’’ (1500 cm-1) bands, assigned to sp2–sp3 bonds in disordered carbonaceous materials and amorphous carbon, respectively. Transmission electron microscopy images showed agglomerates of spherical particles formed by graphitic segments. The results showed that the carbon material obtained from iron N, N -diethyldithiocarbamate, Fe(DDT)3, is structurally better organized than the others and the pore size distribution curves confirmed that this material presents high degree of mesoporosity. Voltammetric curves obtained using KOH and H2SO4 electrolytes showed hysteresis behavior typical of capacitors charge/discharge process. The carbon material prepared from Fe(DDT)3 displayed the highest specific capacitance in acidic media, 59 F g-1, which was associated to its high degree of mesoporosity.

Resumo em Inglês:

In this work, the kinetics of aqueous paraquat (PQ) degradation in a surface air plasma reactor was studied under a variety of experimental conditions. Additionally, stable reactive oxygen species (ROS) and reactive nitrogen species (RNS) were determined. PQ degradation followed pseudo-second order kinetics, increasing both observed rate constant (kobs) and removal efficiency by increasing the temperature. Increasing PQ concentration decreased kobs, as a constant amount of reactive species is generated at the same conditions. Both the decrease of the entropy of activation (–157.1 J K-1 mol-1) and the low value of the enthalpy of activation (+9.9 kJ mol-1) supported a bimolecular associative mechanism for producing the transition state. From the ionic strength effect, the transition state is formed by two ions of opposite charges (zAzB= –3.6). Produced RNS (nitrous and nitric acid) followed zero-order kinetics. Gaseous ozone was the only ROS identified, as hydrogen peroxide concentration was below the limit of detection.

Resumo em Inglês:

Ophioglossum thermale Kom. was fermented with several fungi. The total phenolic and flavonoid contents (TPCs and TFCs) and antioxidant activities of fermented and non-fermented O. thermale (FOT and NFOT) were investigated. The results showed that Talaromyces purpurogenus M18-11 fermented O. thermale possessed significantly improved TPC and TFC and exhibited significantly stronger 1,1-diphenyl-2-picrylhydrazyl (DPPH) (half maximal inhibitory concentration (IC50) = 75.7 ± 2.1 μg mL-1) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) (IC50 = 20.52 ± 1.68 μg mL-1) free-radical scavenging activities, ferric reducing antioxidant power (0.585 ± 0.045 mmol g-1), and reducing power (half maximal effective concentration (EC50) = 30.52 ± 1.91 μg mL-1) than original material. The determination of the contents of representative flavonoids and their glucosides revealed that the improvements are attributed to the hydrolysis of homoisoflavonoid and flavonoid glucosides, glycometabolism, as well as fungal metabolites. This paper is the first to report the fermentation of O. thermale with pure strains and T. purpurogenus is an effective strain to process O. thermale for improving the antioxidant activity.

Resumo em Inglês:

Due to the expansion of sugarcane crops and the high costs of agricultural inputs, an alternative for fertilization of the soil is the use of humic substances (HS) because they improve its physical-chemical properties. The objective of this study was to assess the biological degradation of fipronil in soil supplemented with HS. For determination of fipronil and its metabolites, we validated a quick, easy, cheap, effective, rugged, and safe gas chromatography-mass spectrometry (QuEChERS/GC-MS) method, which yielded detection and quantification limits of 15.0 and 62.5 ng g-1, respectively. The method presented linearity of 0.99, precision between 1.5 and 10.9%, while the recovery ranged from 78 to 98%, with precision (relative standard deviation (RSD)) < 5%. The strain B. thailandensis of Burkholderia sp. grew under typical conditions for degradation of fipronil. Eight treatments assessed the degradation by B. thailandensis in the presence of HS. The metabolites produced in the experiment, although detected, could not be quantified because they were below the limit of quantification of the method. Our results showed that B. thailandensis has the potential to degrade fipronil, and that HS is not toxic to the microbiota, and does not inactivate fipronil.

Resumo em Inglês:

In recent years, ecstasy trafficking has grown in complexity and tablets has been commonly sold containing different contents of 3,4-methylenedioxymethamphetamine (MDMA) or even other psychoactive substances. In contrast, identification and quantification of drugs of abuse is still a challenge, once the access to drug standards is very restricted in Brazil. In this work, ecstasy tablets seized by the Brazilian Federal Police have their chemical composition identified and quantified by gas chromatography and quantitative 1H nuclear magnetic resonance based on an internal standard approach (IS-1H-qNMR). Both methods were validated and showed suitable results for the figures of merit. IS-1H-qNMR shows excellent results of accuracy (relative error < 5%) and precision (relative standard deviation (RSD) < 2%). Comparatively, IS-1H-qNMR is more efficient and versatile than gas chromatography to accomplish in a single analysis the identification and quantification of target analytes. Since the method does not require a specific reference material, it is cost effective and provides agility to routine forensic analysis.

Resumo em Inglês:

Radiation and advection fogs were characterized at two sites nearby important roads next to São Paulo City, Brazil. Water-soluble ions, monosaccharides, other sugars and organic and elemental carbon (OC and EC) were determined. Both sites present a high number of fog events with mainly radiation fogs causing visibility problems to the automotive traffic (Castello Branco and Raposo Tavares roads). Samples were collected in nine events in 2009 and ten events in 2010, during wintertime. Two radiation and advection fog events have been herein presented. The radiation fog occurred in 2009 at Castello Branco Road (CBR), presented the highest concentration of pollutants comparing to all other events. The most abundant species are associated with biomass landfill and fossil fuel burning. Locally, the region has a strong impact by the fertilizer industries and traffic of heavy vehicles. The second most polluted event occurred also in 2009 at CBR, an advection fog presented species attributed to soil resuspension and anthropogenic emissions. The results are compared with rainwater composition studies.

Resumo em Inglês:

This paper presents a simple and low-cost capillary electrophoresis method for ultra-fast simultaneous determination of naphazoline (NPZ) and one of the following active ingredients: diphenhydramine (DIP), pheniramine (PHEN) or chlorpheniramine (CPHEN). The proposed method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) equipped with a short length capillary column (10 cm). One sample can be analyzed every 35 s (ca. 100 injections per hour) with resolutions between peaks greater than 1.4. The optimized background electrolyte (BGE) was composed by 20 mmol L-1 histidine and 10 mmol L-1 3,4-dimethoxycinnamic acid (pH = 9.5, adjusted with NaOH). Limits of detection were 25 µmol L-1 for NPZ, DIP, and PHEN and 13 µmol L-1 for CPHEN. The results obtained with the developed procedure were compared to those obtained by high-performance liquid chromatography (HPLC) and no statistically significant differences were observed (95% confidence level).

Resumo em Inglês:

Surface modification of poly(GMA-co -EDMA-co -MMA), whose synthesis was performed by copolymerization of 2,3-epoxypropyl methacrylate (GMA), methyl methacrylate (MMA), and ethylene glycol dimethacrylate (EDMA), was compared between aliphatic and aromatic substituted resorcarenes. The copolymer surface was modified by reacting with resorcarenes, and the vibrational properties of the modified copolymers were investigated via attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectroscopies in dry state at room temperature. Those analysis showed that only tetra(p -hydroxyphenyl)resorcarene was linked to the copolymer, the reaction was regioselective with the crown conformer. Additionally, quantification of incorporated macrocyclic was performed, specifically, the maximum fixation of resorcarene in the copolymer was 95% when employing two molar resorcarene excesses per glycidyl residue. The modification was carried out in both acidic and basic medium and it was established that the polymer is modified with the aromatic resorcarene only in basic medium, while the reaction in basic medium with aliphatic resorcarenes produces their corresponding tetrasodium salt.

Resumo em Inglês:

The Mehlich-1 extractor is routinely used to evaluate the bioavailability of metals in soil since it has a high closeness between the amount of these elements absorbed by the plants and those available in soil, as well as being simple and practical to use. Thus, the aim of this work was to improve (optimize) a Mehlich-1 extraction method for evaluating the availability of Cu, Zn, Mn, Ni, Cr and Cd in soil using Box-Behnken type response surface method (RSM). After optimizing the soil amount, Mehlich-1 extractor volume and stirring time, the validation of the newly developed method was performed by evaluating the following parameters: matrix adjustment, linearity, linear range, limits of detection (LOD) and of quantification (LOQ), precision and accuracy. The analytical method proposed by this study can be routinely employed for the evaluation of soil toxicity since it presented advantages such as simplicity, speed and efficacy, as well as being precise and accurate.