Resumo em Inglês:

Different activated carbons and manganese-modified activated carbons were prepared as deoxidizers for the low-concentration coalbed methane deoxidation. The results show that the deoxidation performance of the different activated carbons is affected by raw materials for preparation of deoxidizers. One type of activated carbon exhibited the best performance of oxygen removal, due to the relatively low ash content and better adsorption performance. Experimental results show that the manganese-modified deoxidizers exhibit an excellent deoxidation efficiency at low temperature. At 200 ºC, one kind of manganese-modified activated carbons decreased the oxygen content to less than 1 vol%, which could maintain about 600 min. This indicated that the addition of manganese greatly improved the reactivity of oxygen with activated carbon. Characterization results demonstrated that the physical structure and species types of oxygen of activated carbons, and manganese have important effects on the activity of deoxidizers in different temperature ranges.

Resumo em Inglês:

Release behaviors of arsenic (As) during pyrolysis of two Chinese coal gangues were studied in this report. The pyrolysis experiments were carried out in a temperature programmed tube furnace under N2 atmosphere with different temperature (200-1200 ºC), residence time (0-50 min), heating rate (10-50 ºC min-1) and N2 gas flow rate (100-500 cm3 min-1). The experiment results, under different pyrolysis conditions, indicate that the release ratio of As increases with increasing temperature, as well as residence time during pyrolysis of coal gangues. Besides that, higher heating rate during pyrolysis of coal gangues can stimulate the As release from coal gangue to some extent. The release ratio of As increases to a maximum and then decreases when the N2 gas flow rate is increased. The results imply that different modes of ocurrence of As exist in two coal gangues. The As release has positive relation with the volatile matter release. As is more easily released than coal gangue matrix during coal gangue pyrolysis.

Resumo em Inglês:

Hydrated Mn/Al-SO4-A (A = Li, Na or K) layered double hydroxides with M2+:M3+ molar ratio close to 1:1 were synthesized by co-precipitation with increasing pH. All phases presented solvated alkali metals and sulfate as intercalated species. In the exchange reactions, when sulfate solutions of alkali metals were used, sodium could be partially replaced by potassium, and the same was true for the potassium phase, where potassium could be partially replaced by Na and Li, without removing the intercalated sulfate anions. This class of compounds, considered to be anion exchanger, can also exchange cations, which opens new perspectives for applications.

Resumo em Inglês:

A novel method for the determination of aflatoxins B1, B2, G1, and G2 (AFB1, AFB2, AFG1, AFG2) in animal feed samples based on magnetic solid-phase cleanup and novel pre-column derivatization has been developed. In this work, synthesized polyvinylpyrrolidone-coated Fe3O4 magnetic nanoparticles were applied as adsorbents for rapid cleanup for extracts of animal feed samples. The purified extract was then derivatized with trifluoroacetic acid coupling ultraviolet irradiation which enabled the weakly fluorescent AFB1 and AFG1 transformed into their highly fluorescent hemiacetals derivatives. Afterward aflatoxins were separated and quantified by reverse phase liquid chromatography with fluorescence detection. The results indicated that four AFs presented excellent linear response with correlation coefficients > 0.996 and recoveries ranged from 86.7 to 108.9% with relative standard deviations (RSDs) from 3.6 to 6.4%. The limits of detection (LODs) were 0.0392, 0.2429, 0.0842, 0.4556 ng mL-1 for AFB1, AFB2, AFG1 and AFG2, respectively.

Resumo em Inglês:

In this work, we report the preparation of a copper-silica material (Cu/SiO2) by a sol-gel methodology and its characterization concerning composition and textural properties. The Cu/SiO2 material was successfully applied as a Lewis acid heterogeneous catalyst for the A3-coupling from 2-aminopyridine, aldehydes and alkynes to imidazo[1,2-a]pyridines (45-82%), which are relevant pharmacological scaffolds. The synthesis shows a number of advantages, such as easy separation from the reaction media and the minimal formation of metal aqueous wastes. Investigation of the mechanism supports the involvement of the formation of reaction intermediates inside the pores of the mesoporous material prior to 5-exo-dig cyclization.

Resumo em Inglês:

Dithiocarbamates are widely used fungicides, including in passion fruit, whose fruits are mainly used for juice production, the leaves for the preparation of herbal tea and medicines. Also, the use of the peel in the food industry has been proposed. In this study, the spectrophotometric method for determination of dithiocarbamate residues, as CS2, in passion fruit (Passiflora edulis) was validated at a limit of quantification (LOQ) of 0.05 mg kg-1 CS2, and 108 samples (55 fruits and 53 leaves) collected from Brazilian growers were analyzed. About 25% of the fruit peel samples were positive (0.06 to 1.4 mg kg-1) and only one sample had residues in the pulp (0.09 mg kg-1), 43.4% of leaf samples contained residues. Washing of fruit reduced the residues in the peel by up to 100%, and drying the leaves increased residue levels by up to 60%. This is the first study that reports dithiocarbamate residues in passion fruit in Brazil, and the results are important for government authorities when planning monitoring programs, and for food and herbal medicine industries.

Resumo em Inglês:

Dengue is one of the most prevalent infectious tropical diseases in the world, with high incidence in over 100 countries. Rapid and reliable diagnosis of dengue is of great importance for public health. To simplify molecular diagnostics, isothermal amplification techniques have recently emerged as an alternative to conventional methods of deoxyribonucleic acid (DNA) amplification. Here, we developed a one-step method for dengue virus detection from real sample based on RT-LAMP (reverse transcription-loop mediated isothermal amplification) in a disposable microdevice. The reaction was thermally controlled with a thermoblock for 15 min at 72 ºC. At the end of the incubation time, we either removed the solution for detection of fragments by gel electrophoresis or added DNA intercalator for visual detection on-chip. Our results demonstrated that it is possible to detect dengue virus through RT-LAMP directly from a serum sample, without previous ribonucleic acid (RNA) extraction. The success of RT-LAMP was confirmed in reactions initiated with 0.8 fg µL-1 of RNA, which represents 200 copies of RNA per µL. RT-LAMP in a polyester-toner (PeT) microdevice is a simple and inexpensive method that allows for rapid detection of dengue virus with high reliability and great potential for point-of-care applications.

Resumo em Inglês:

The sensitive and selective chemosensor for copper(II) ions (Cu2+) was successfully optimized using the 1,5-diphenylthiocarbazone (DPT) compound. The result showed that dimethyl sulfoxide (DMSO) in a 9:1 (DMSO:water) ratio at a pH of 3 was the optimum medium for DPT to act as chemosensor of Cu2+ recognition. The DPT chemosensor did not encounter any interference from other metal ions, including Fe3+, Ag+, Cr3+, Pb2+, Mg2+, Cd2+, Zn2+, K+, Ni2+ and Co2+. The presence of Cu2+ led to an absorption peak at 658 nm, where the color changed from cantaloupe to gray-green color indicating the interaction by the formation of the DPT-Cu complex in 2:1 stoichiometry. The theoretical s-profile calculation using conductor-like screening model for real solvents (COSMO-RS) showed the compatibility of DPT with the DMSO solvent through hydrogen bonding. In the density functional theory (DFT) calculations, the formation energy of DPT and DPT-Cu were -1113.79645660 and -2435.71832681 a.u. , respectively. Under optimal conditions, a detection limit of 6.08 µM for the DPT chemosensor for Cu2+ recognition can compete with the flame atomic absorption spectroscopy (FAAS) value of 6.21 µM. Finally, DPT was able to provide less expensive, more portable and convenient chemosensor for Cu2+ recognition in environmental water samples.

Resumo em Inglês:

Three molecular hybrids containing 1,4-naphthoquinones, 1,3,5-triazines, morpholine and 7-chloroquinoline, which have recognized contributions to the biological activity of many drugs, were synthesized in yields ranging from 43-84%. All hybrids were obtained in three steps starting from readily available reactants: lawsone, cyanuric chloride, morpholine and 4,7-dichloroquinoline. A previous docking study was carried out to identify the binding energy and pharmacophore conformation of the promising anticancer compounds with PI3Kγ (phosphoinositide 3-kinase) and AMPK (5’ AMP-activated protein kinase). The cancer activity in human metastatic melanoma cells (SKMEL-103) were performed, and the synthetized compounds presented half maximal inhibitory concentration (IC50) values around 25 µM. The expressions of PI3K and AMPK were also determined using western blotting technique, and all molecular hybrids negatively modulated both targets.

Resumo em Inglês:

A dipyridamole (DIP) based surface molecularly imprinted polymer (MIP) was synthesized and applied as a sensing agent in a sensing layer of a new modified potentiometric carbon paste electrode (CPE). The potentiometric modified CPEs (GO@SiO2-NH2-MIP/MWCNTs/CPE, where GO is graphene oxide and MWCNTs is multi-walled carbon nanotubes) showed an improved performance in term of Nernstian slope, selectivity and response time compared to the unmodified CPE. The response time of the sensor in the range of 2.5 × 10-8-1.1 × 10-2 M DIP was 20 s. The obtained DIP sensor showed low limit of detection (1 × 10-8 M), and satisfactory long-term stability (higher than 4 months). The practical application of the sensor was demonstrated by the determination of DIP concentration in urine samples and pharmaceutical preparations, with good precision and acceptable recoveries (96.0-103.0%). The prepared sensor showed high selectivity for DIP over a number of common species (aspirin, caffeine, ascorbic acid, glucose, urea, bipyridine, Na+, Fe3+, Mg2+, Ca2+ and K+).

Resumo em Inglês:

The inorganic composition of the bark and leaf of a plant from the Amazon rainforest, Andira surinamensis, was determined using two non-destructive, multi-element techniques: X-ray fluorescence (XRF) and Rutherford backscattering spectrometry (RBS). XRF measurements were made using both a conventional X-ray source and synchrotron radiation. It was observed that although magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, and potassium are present in higher concentrations in the leaf, calcium is about three times more concentrated in the bark. Manganese, iron, copper, zinc, strontium and barium were also detected, with barium showing a concentration above the minimum toxicity level for plants. Chemical speciation of sulfur, performed using the X-ray absorption near edge structure (XANES) technique, showed that sulfur is present in several oxidation states, with a much larger contribution from the inorganic sulfate in the leaves. The article evidences that the combined use of synchrotron radiation and non-destructive multi-element techniques allows for an efficient and accurate determination of the inorganic composition and chemical speciation in plants.

Resumo em Inglês:

Using niobium compounds as heterogeneous catalysts in biodiesel production is a promising methodology from economic and environmental viewpoints. However, the application of niobium catalysts still is a challenge due to the high temperatures and pressures for moderate biofuel yields. Therefore, easily handled and applied materials have been developed to optimize biofuel production, which is the goal of this study. Nb2O5 and ammonium niobium oxalate (AmNO) were activated in reflux and ultrasound-assisted system. Nb2O5 showed better activity under reflux, using methanol. The characterizations conclude that the Lewis-acid sites are determinant for higher conversion rather than surface area. AmNO has better activity also in the reflux system at 70 ºC, against 170 ºC for Nb2O5, reaching above 70% conversion. In addition, reactions in ultrasound-assisted systems are also appealing due to the lower time and temperature, with conversion rates above 40%. Both catalysts showed interesting results under milder conditions than those in the literature.

Resumo em Inglês:

Seasonal concentrations of total, particulate and dissolved Al, Cu, Cd, Cr, Fe, Pb and Ni were analyzed in surface water and total metals in sediment samples from black and whitewater rivers within the Itacoatiara City, Central Amazon. Metals concentrations in water and sediment samples demonstrated that even though urbanization and agricultural practices are common in this region. Metal concentrations in sediments samples are acceptable regarding the recommended levels for protection of aquatic life. From this work, which is the first trace elements study in the main tributaries from Itacoatiara region, we conclude that metals are present in a particulate form, being easier to be transported to other aquatic bodies. During flooding periods an increase of Al, Fe and total organic compound (TOC) in almost water sampling points was observed.

Resumo em Inglês:

Chalcones are compounds with wide interesting biological activities including Alzheimer’s disease. A comparative study was performed between the chalcones (E)-1-(2-aminophenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one and 1-(6-amino-1,3-benzodioxol-5-yl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one regarding the influence of benzodioxol group on their molecular conformations. The first chalcone was neutralized with dilute hydrochloric acid, while solid of the second was filtered and recrystallized from ethanol, both on centrosymmetric space group P21/c. Their molecular packing were evaluated by Hirshfeld surfaces, and both frontier molecular orbitals and molecular electrostatic potential (MEP) map were carried out by density functional theory (DFT) calculations. The compounds are stabilized by C–H…O and C–H…p interactions, as observed on MEP map, while the HOMO-LUMO gap indicated the conformational stability. The pharmacophore mapping approach was carried out for the identification of potential target candidates and then, further molecular docking analysis targeting the beta-secretase 1 (BACE-1) protein as a tactic to develop potential AD inhibitors, was performed. The AutoDock Vina score in redocking result for 2OHQ is –7.4 and –7.6 kcal moL-1. Additionally, the docking results for compounds inside the active site of the 2OHQ structure showed that both compounds bound to the BACE-1 active site with AutoDock Vina score of –6.0 kcal moL-1.

Resumo em Inglês:

A hand-held near infrared (NIR) spectroscopy device is much more convenient than a traditional desktop NIR instrument. Thus, it is more suitable for the practical application. An automatic and rapid tool for grading tobacco leaves on the spot using a hand-held digital light processing (DLP)-based NIR spectroscopy device is proposed in this paper. Firstly, the spectral data of the samples is scanned with a hand-held NIR device directly from the tobacco leaves without any samples preparation procedures. Then, the training model of different classes is built and the class of each test sample is predicted by using sparse representation classification (SRC) algorithm. Comparing with the traditional linear discriminant analysis (LDA) and support vector machine (SVM) algorithms, the classification accuracy of SRC method is the highest and has the least computation time. The results show that hand-held NIR spectroscopy technology could be a novel classification tool for grading tobacco leaves in the purchasing on the spot.

Resumo em Inglês:

Removal of toluene using cobalt oxide supported on sepiolite catalysts was investigated. Deposition precipitation method was used to prepare the catalysts. The catalysts were characterized using X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis (TGA) and Brunauer-Emmet-Teller methods. The results of catalytic testing showed that 20% cobalt oxide/sepiolite (Co20/Sep) had higher catalytic activity for degradation of toluene. A temperature of 400 ºC was found to be the optimum calcination temperature for Co20/Sep, since it achieved 90% toluene conversion at about 300 ºC. The results showed that the selectivity of the catalysts towards CO2 was complete and no byproducts were detected. Stability tests also indicated that Co20/Sep remains stable at 320 ºC with complete conversion of toluene after 24 h. In conclusion, the results of this study confirmed sepiolite-supported cobalt oxide catalyst as an efficient catalyst for degradation of toluene.

Resumo em Inglês:

In this study, a polymer pH-indicator was synthesized by sulfonation of poly(styrene-co-acrylic acid) with concentrated sulfuric acid. The synthesized polymer pH-indicator exhibited pH-responsive color changes in aqueous solutions, being purple in alkaline medium (pH < 4), whereas yellow in acidic medium (pH > 9). The sulfonation process extent and polymer color were affected by time and temperature of the process, as well as acrylic acid (AA) content. The addition of acrylic acid was a crucial point for color change due to the facility of cyclic ketone structure to turn into phenol under acidic condition. Compared with low molecule pH-indicators, the sulfonated copolymer was prepared in form of films being repeatedly used as pH-indicator and easily removed from the acid-base medium.

Resumo em Inglês:

In this paper, a simple, sensitive and precise electroanalytical method was developed using a chemically-reduced graphene-oxide (CRGO)-modified glassy carbon electrode and square wave voltammetry (SWV) for determination of ciprofloxacin in pharmaceutical formulations (tablets) and milk samples. Advantages of this sensor include a potential displacement of 100 mV and a 5-fold current increase for the electrochemical oxidation of ciprofloxacin, which resulted in a highly sensitive sensor, when compared to unmodified electrode. The improved properties of the modified electrode are likely due to the formation of a porous surface evidenced by the change in electrode kinetics (thin-layer diffusion process). The proposed sensor is free from interference of sample matrix (pharmaceutical formulations and low/high-fat milk) avoiding cumbersome processes such as previous separations, solvent extraction, or sample filtration (samples were only diluted in Britton-Robinson buffer solution). The results by SWV showed a limit of detection of 0.21 µmol L-1 (correspondent to 0.069 mg L-1), which is lower than the ones obtained using other carbon-based electrodes, relative standard deviations lower than 12%, and satisfactory recoveries in the range from 84 to 109%. The results obtained were statistically similar (95% confidence level) with those performed through high-performance liquid chromatography (HPLC).

Resumo em Inglês:

Agrosilvopastoral waste, regarding agriculture and agro-industry sectors, is pointed as a promising sustainable raw material for biofuels production, specially concerning exploitation of lignocellulosic organic residues for fermentable sugars and cellulosic ethanol output, being therefore necessary to investigate the potential of these substrates concerning chemical composition, since many of them were not reported yet in literature. Being so, this paper presents a study of chemical composition and enzymatic hydrolysis of wastes from the four main crops in Maranhão, Brazil (soy, cassava, rice and corn) which are usually underutilized or abandoned in the field. The results of enzymatic hydrolysis were satisfactory for both soy and particularly corn residues, which presented total reducing sugars (TRS) percentage greater than 50% in comparison with pure cellulose.

Resumo em Inglês:

In this work, the gas diffusion electrode (GDE) cathode of Vulcan XC72 carbon modified with nanoparticles of WO2.72 (WO2.72 / Vulcan XC72) was used for H2O2 electrogeneration and degradation of 350 mL of Orange II (OII) and Sunset Yellow FCF (SY) azo dyes by electro-Fenton (EF) and photoelectro-Fenton (PEF) processes with different Fe2+ initial content (1.00, 0.50 and 0.25 mmol L-1). The WO2.72 / Vulcan XC72 GDE electrolyzed approximately 3 times more H2O2 than the Vulcan XC72 GDE. Decolorizations and mineralizations of the dye solutions were more efficient at higher concentrations of Fe2+. The decolorization decay showed pseudo-first-order kinetics. The most promising decolorization results obtained at processes of WO2.72 / Vulcan XC72 cathode combined with Pt anode (100% color removal of OII and SY at 30 and 20 min of electrolysis with 1.00 mmol L-1 Fe2+, respectively). The best mineralization achieved in trials of WO2.72 / Vulcan XC72 cathode combined with boron-doped diamond (BDD) anode (82% total organic carbon (TOC) removal of OII by PEF / 1.00 after 3 h and 90% TOC removal of SY by PEF / 0.50 after 4 h). It was found that SY decolorization was faster and mineralization showed a similar yield independent of oxidized dye.

Resumo em Inglês:

Catalysts were prepared by the heterogenization of the tributyltin(IV) methoxide (n-Bu3Sn(OMe)) and dibutyltin(IV) dimethoxide (n-Bu2Sn(OMe)2) on silica by two strategies: (i) anchoring of the organotin(IV) compounds on silica and (ii) anchoring of the organotin(IV) compounds on a silica gel functionalized with mercaptopropyl groups (SiO2–SH). The characterization results showed that, regardless of the method used to anchor the organotin species, the solids contained approximately 7-10% of Sn. The decrease or disappearance of the O–H and S–H stretching signals in the SiO2 and SiO2–SH spectra after the treatment with the organotin(IV) methoxide derivatives suggest the immobilization via O–Sn or S–Sn covalent bonds. The catalytic performance was evaluated in methanolysis of ethyl acetate, in comparison to the analogous homogeneous systems, and the order of reactivity is n-Bu2Sn(OMe)2 > n-Bu3Sn(OMe) > SiO2–SnBu2 > SiO2–S–SnBu2 > SiO2–SnBu3 > SiO2–S–SnBu3. The solids on which the organotin species were directly immobilized on activated SiO2 showed catalytic efficiencies slightly higher than those immobilized on thiol-functionalized silica. All of the solid catalysts were recovered and reused for recycling studies and characterized again after the reuse tests. A better interaction between n-Bu3Sn(OMe) and both supports was observed, as verified by the low leaching of Sn after the first catalytic reaction.

Resumo em Inglês:

This study describes the use of uncured polydimethylsiloxane (PDMS) as a binder agent to prepare carbon paste electrodes (CPEs). A comparative study between the properties of CPEs prepared with PDMS and mineral oil Nujol®, the most common binder agent for CPEs, was carried out. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry showed that PDMS-CPEs presented higher electrical conductivity, active electrochemical area, and wider useful potential window compared with Nujol®-CPEs. Moreover, PDMS-CPEs were more stable in aqueous mixtures containing 50% (v/v) of ethanol or methanol than Nujol®-CPEs. PDMS-CPEs have also provided higher sensitivity and lower limit of detection to propranolol than Nujol®-CPE. Therefore, this study demonstrated that PDMS is a promising alternative binder agent able to produce CPEs with superior chemical/electrochemical stability and improved analytical performance.