Journal of the Brazilian Chemical Society This is an RSS file. You can use it to subscribe to this data in your favourite RSS reader or to display this data on your own website or blog.

Evaluation and Geostatistical Study of Toxicological Risk by Water Ingestion with Al, Ba, Fe and Pb in Communities Close to Industrial Areas in the Brazilian Amazon
This study provides a risk assessment and risk maps related to the consumption of water contaminated by Al, Ba, Fe and Pb in an industrial area in the Brazilian Amazon. A total of 120 samples of drinking water were collected from 26 locations in the municipality of Barcarena, Par á State. Multiple elements were analyzed by inductively coupled plasma optical emission spectrometry. The quantifiable elements in the samples were Al, Ba, Fe and Pb. Risk assessment was performed according to U.S. Environmental Protection Agency (USEPA) procedures. Results indicate that the highes t potential risk of non-carcinogenic adverse hea...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Voltammetric Determination of Free and Total Manganese in Tea Infusions
Tea infusions are a source of mineral nutrients, including manganese. Although it is classified as an essential element, the excess of manganese is toxic for humans and its toxicity depends on its bioavailability. In this context, we propose a simple procedure to determine free and total manganese in black tea infusions by square-wave voltammetry (SWV). Free manganese was directly quantified in the samples after simple sample dilution in 0.1 mol L − 1 acetic acid/acetate buffer (pH = 4.5) while total manganese determination was carried out after sample digestion with oxidant mixture (HNO3 + H2O2). For comparison, cloud p...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Chemical Prospection of Qualea grandiflora Mart. Fruit and Stem Extracts and Their in vitro and in vivo Antiplasmodial Activity
In this study, we investigated the antiplasmodial activity of Q. grandiflora fruit and stem extracts against Plasmodium falciparum. The polar extracts of both fruits and stems showed promising in vitro antiplasmodial activity against sensitive and resistant P. falciparum strains (half-maximal inhibitory concentration (IC50) = 1.2 and 4.2 ng mL-1, respectively), low cytotoxicity against human hepatic cells (IC50HepG2 ≥ 400 ng mL-1), and a noteworthy selectivity index (SI ≥ 322 and ≥ 96, respectively). The fruit ethanolic extract revealed significant oral efficacy at 100 mg kg-1 in a mouse model of P. berghei malari...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Simultaneous Quantification of Plasma Catecholamines and Metanephrines by LC-MS/MS
The quantification of the low levels of catecholamines and metanephrines in biological fluids is important for clinical screening of pheochromocytoma/paraganglioma and diagnosis of overtraining syndrome in athletes. We introduce a novel, accurate and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of these biogenic amines in human plasma. Simple protein precipitation combined with rapid 2-aminoethyl diphenylborinate-assisted liquid-liquid extraction allow us to quantify catecholamines and metanephrines over broad concentration ranges. Target analytes were monitored...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Two Years Monitoring of Ethyl Carbamate in Sugar Cane Spirit from Brazilian Distilleries
This paper describes the monitoring of ethyl carbamate concentration in sugar cane spirit from industrial distilleries in Brazil. In total, 18 distilleries from Minas Gerais and S ão Paulo states were evaluated, with, a total of 336 samples from August 2017 to August 2019. The ethyl carbamate was analyzed using a previously validated mass spectrometric method. Analytical curves presented coefficient of determination (R2) values higher than 0.99, and quality control samples s howed a relative standard deviation (RSD) below 9%. Concentrations of ethyl carbamate ranged from not detected to 1608 µg L-1, with mean values of 2...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Fast Verification of Buffalo’s Milk Authenticity by Mid-Infrared Spectroscopy, Analytical Measurements and Multivariate Calibration
Mid-infrared spectroscopy (MID), chemical composition and physicochemical characteristics associated with chemometrics were used to rapidly detect and quantify the amount of cow ’ s milk added in buffalo ’ s milk. A total of 165 samples, divided into buffalo ’ s milk, buffalo ’ s milk added with cow ’ s milk (10 to 90%) and cow ’ s milk were evaluated to obtain fat, protein, lactose, total and defatted solids, urea, pH, acidity, cryoscopic index and band absorbances in the spectra associated with principal component analysis (PCA), multiple linear regression (MLR) and partial least squares regression (PLS). The...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Concentration of Metals in Plant Litter Produced in Regions of Caatinga in Southwest Bahia, Brazil
The objective of this study was to investigate the concentration of metals (Fe, Co, Ca, Cu, Ni, Mg, Mn and Zn) in Caatinga plant litter in the southwest region of Bahia. Plant litter was collected in summer (January/2017) and winter (August/2017). Concentrations were determined by flame atomic absorption spectrometry (FAAS). The results were submitted to multivariate analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA). The average amount of plant litter found in January and August was 1190 and 1329 kg ha-1, respectively. The twigs fraction provided the largest amount of biomass to the plan...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

A Comparative Study on the Groebke-Blackburn-Bienaymé Three-Component Reaction Catalyzed by Rare Earth Triflates under Microwave Heating
Over the last twenty years, the Groebke-Blackburn-Bienaym é (GBB) reaction has been emerged as a powerful tool to access different nitrogen-based heterocycles as privileged scaffolds in medicinal chemistry. This multicomponent reaction is usually catalyzed by ordinary Brønsted or Lewis acid catalysts. Herein, we present a comparative study on the catalyt ic efficiencies of different rare earth triflates in GBB reactions under microwave heating, involving 2-aminopyridine or 2-aminothiazole, as aminoazole component, and different aldehydes and aliphatic isocyanides. The use of gadolinium(III) triflate as cheaper alternativ...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Mango (Mangifera indica) Aroma Discriminate Cultivars and Ripeness Stages
In this study, it was demonstrated that both the variety and ripening stage have a significant impact on the aroma of mango. The volatile compound profile of “ Tommy Atkins ” , “ palmer ” , “ espada ” and “ Carlota ” varieties in green and ripe stages were characterized by headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME/GC-MS). Thirty-three volatile compounds were identified, 30 from “ Tommy Atkins ” , 29 from “ espada ” , 25 from “ palmer ” and 10 from the “ Carlota ” variety. The major compounds were monoterpene and sesquiterpene hydrocarbons, regard...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Application of a Chemometric Method to Interpret Spectrophotometric Data Obtained for Degradation of an Organic Dye in Water Using Manganese Oxide
Birnessite type manganese oxide ( δ -MnO2) was synthesized for use in degradation of the cationic dye methylene blue in aqueous solution. The material was characterized using infrared spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller (BET) surface area calculations. The removal of the dye from aqueous solutions was evaluated considering the effects of the following variables: pH, manganese oxide concentration, contact time, and temperature. UV-Vis spectroscopy analyses indicated achievement of 99 and 95% removal of methylene blue (7 mg L-1) at pH 2.0 and 4.0, respectively, after 120 min of contact with the birne...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

High Conversion of Palm Olein to Ethyl Esters Using a Strong Anion Exchange Resin: Study of the Operational Parameters
Biodiesel, known as a mixture of fatty acid ethyl/methyl esters, is seen as an alternative, ecofriendly, biodegradable and renewable non-fossil fuel. The use of heterogeneous catalysts for biodiesel synthesis can solve several problems associated with the homogeneous alkaline catalyzed-transesterification. Therefore, this work reports the evaluation of the commercial resin Amberlyst A26OH, a strong anion exchange resin, as a heterogeneous catalyst for the batch transesterification of refined palm olein with ethanol. It was studied the effects of the main operational parameters, considering the molar ratio of the reaction m...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Hopfield Neural Network-Based Algorithm Applied to Differential Scanning Calorimetry Data for Kinetic Studies in Polymorphic Conversion
A general kinetic equation to simulate differential scanning calorimetry (DSC) data was employed along this work. Random noises are used to generate a thousand data, which are considered to evaluate the performance of Levenberg-Marquardt (LM) and a Hopfield neural network (HNN) based algorithm in the fitting process. The HNN-based algorithm showed better results for two different initial conditions: exact and approximated values. After this statistical analysis, DSC experimental data at three heating rates for losartan potassium, an antihypertensive drug, was adjusted by the HNN method using different initial conditions to...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Production of Furanic Compounds and Organic Acids from Brazilian Pequi (Caryocar brasiliensis Camb.) Residues Using Green Chemistry
In the current search for renewable energy sources, residual biomass has gained ground in the concept of biorefinery. Furanic compounds such as 5-hydroxymethylfurfural (HMF), furfural (FF) and derivatives such as levulinic acid (LA), obtained from biomass, have emerged as important industrial chemical platforms. In this sense, this work aimed to use pequi bark, typical biomass and abundant in the Brazilian cerrado, in the production of HMF, FF and LA using the ionic liquid 1-n-butyl-3-methyl-imidazole bromide ([BMIM][Br]). The analysis of chemical composition of pequi bark showed that it has potential for use in the produc...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Understanding Solvent/Bixin Interactions by Raman Spectroscopy
In this work, Raman spectroscopy and density functional theory (DFT) calculations have been used in order to understand the nature of the interaction between the carotenoid bixin and organic solvents with dielectric constant varying from ca. 2 (toluene) to ca. 47 (dimethyl sulfoxide). Raman shifts registered for the main carotenoid marker band, the C=C stretching mode (1525-1533 cm-1), were used as a probe to monitor spectral changes due to chemical interaction between bixin in the solid state with the analogous solvated species. Raman spectra of bixin in solution showed significant bathochromic shifts in the wavenumber po...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research

Furfural Hydrodeoxygenation over a Ruthenium-Based Bifunctional Catalyst in the Presence of a Direct Source of H2
This work presents the results obtained for the gas chromatography-mass spectrometry (GC-MS) monitoring of the liquid-phase hydrodeoxygenation (HDO) reaction of furfural (FFR) to 2-methylfuran (MF) over a bifunctional Ru/RuOx/C catalyst in the presence of a direct source of H2. Hydrogenation and hydrogenolysis reactions of FFR and of the intermediate furfuryl alcohol (FA), respectively, were independently studied to provide insights on the HDO mechanism. The mass spectra monitoring of the kinetic isotope effect indicated the HDO reaction occurs through a two-step mechanism comprising of an initial ruthenium-mediated hydrog...
Source: Journal of the Brazilian Chemical Society - July 3, 2020 Category: Chemistry Source Type: research