Resumo em Inglês:

The present paper concerns to predict the sulfur concentration in biodiesel/diesel blends in the range of 5-100 mg L-1 of sulfur using spectrofluorimetry and partial least squares multivariate calibration (PLS). The calibration set consisted of samples with 10 and 20% (B10 and B20) of biodiesel in diesel with sulfur addition of 5-100 mg L-1. Two PLS models were constructed, one to predict the concentrations of sulfur in B10 blends that presented coefficient of determination (R2) values of 0.9867377 and 0.9801064, respectively, for calibration and validation. The other PLS model predict the concentrations of sulfur in B20 that presented R2 values of 0.9949219 and 0.8573713, respectively, for calibration and validation. Therefore, the models showed adequate efficiency to predict changes in the concentration of sulfur in biodiesel/diesel blends B10 and B20.

Resumo em Inglês:

A series of carbon nanotube (CNTs)-supported copper-cobalt catalysts were prepared and investigated in a slurry reactor for their ability to selectively convert syngas into higher carbon number alcohols. The 7.5Cu7.5Co/CNTs catalyst achieved superior selectivity towards the formation of ethanol (30.1%) and C2+ alcohols (57.7%), while the 10Co5Cu/CNTs catalyst exhibited the largest alcohol space-time yield (372.9 mg gcat -1 h-1). However, the pure Cu (15Cu/CNTs) catalyst displayed negligible activity. Cobalt reduction was enhanced in the presence of copper. In addition to the Cu0-Co0 center, Co0-Co2+ also presented dual active sites for higher alcohols synthesis, the Co2+ site could terminate carbon chain growth to produce alcohols. The ratio of Cu/Co considerably influences the metal particle properties-synergistically effecting the active species.

Resumo em Inglês:

This paper presents a new green protocol for Knoevenagel condensations of aldehydes and compounds with an active methylene group in a binary mixture of ethanol/water (3:7, v/v). This medium favored the uncatalyzed Knoevenagel reactions and easy workup products can be obtained by precipitation in this medium and showed good isolated yields (55-100%) in short reaction times (1-60 min).

Resumo em Inglês:

A new fluorophore containing 2,1,3-benzothiadiazole unit with alkylated tetrazole terminal groups as electron donors connected through a π-conjugated system of the type (D-π-A-π-D) was synthesized using the Sonogashira coupling reaction with good yields. The genotoxicity of the two intermediate compounds and the final product was evaluated in vitro in consideration of the potential application of the new compound in the chemical production of photovoltaic paints. The new fluorophore did not show significant biological effects in the cell viability test and the comet assay when compared with the intermediate compounds that were obtained synthetically despite the ability to interact with deoxyribonucleic acid (DNA) as demonstrated in circular dichroism assays. Thus, the compound does not show toxic or genotoxic activity, and therefore, it can be applied as a pigment in photovoltaic paint.

Resumo em Inglês:

Formaldehyde is a carcinogenic compound that was employed as fungicide in the past. Despite its disuse, some foods such as mushrooms naturally produce formaldehyde, showing the importance of its determination. In this work, a mechanized flow system based on solenoid valves is proposed for spectrophotometric formaldehyde determination in mushrooms. The analyte was extracted from fresh and dried mushrooms samples by steam distillation with deionized water in the presence of phosphoric acid. The determination was based on the reaction between formaldehyde and acetylacetone in presence of ammonium acetate (Hantzsch reaction), leading to the formation of 3,5-diacetyl-1,4-dihydrolutidine (DDL, λmax = 412 nm). Linear response from 0.2 to 7.0 mg L-1 was achieved, with detection limit estimated at 0.02 mg L-1 (99.7% confidence level). Coefficient of variation and sample throughput were 1.1% (n = 15) and 17 h-1, respectively. Per determination, 11 mg of acetylacetone and 30 mg of ammonium acetate were consumed, generating 4.2 mL of waste. The procedure was applied to formaldehyde determination in fresh and dried shiitake, and fresh shimeji, and the results agreed with those attained by reference method at the 95% confidence level.

Resumo em Inglês:

Traditionally, thermokinetic and chemical oscillations have been studied independently, but in cellular media recent studies have shown that cell’s temperature is not uniform. Thus, on this context it is possible to inquire about the influence of thermal effects on chemical oscillatory behavior and vice versa. To this end, in this paper we propose a dynamical model based on a modified Sal’nikov oscillator that can address both kinds of oscillatory behavior (thermokinetic and chemical). We found that the system modeled can jump from thermal oscillations to mixed chemical-thermal oscillations through a transition or bifurcation parameter. Thermokinetic oscillations are well defined in a limit cycle, while chemical-thermal oscillations appear in the form of a burst. The model could be useful in explaining biochemical energy recovery under cellular stress conditions.

Resumo em Inglês:

One new methodology for analysis of the antimicrobial oxolinic acid (OXA) based on adsorptive stripping voltammetry (AdSV) in carbon paste electrode (CPE) was developed and applied in untreated pond water sample. Cyclic voltammetry (CV) indicated that an irreversible anodic process occurs in KOH solution as supporting electrolyte. Quantification of the antimicrobial was carried out by differential pulse adsorptive stripping voltammetry (DPAdSV) at potential of deposition (ED) +1.05 V for 45 s to examine OXA adsorption on the surface of CPE. The limits of detection (LOD) and quantification (LOQ) of the method for OXA analysis were determined. The values of LOD were 0.0570 and 0.512 mg L-1 in absence of matrix and in the water sample, respectively, and the corresponding values of LOQ were 0.192 and 1.707 mg L-1, respectively. The apparent recovery percentage for different concentrations of OXA in natural waters ranged between 98.4 and 109%.

Resumo em Inglês:

A wet-synthetic method is described to obtain magnetic, air-stable, zero-valent iron nanoparticles coated with an alkanedioic acid. The particles can be immobilized in an amino-substituted polysiloxane matrix to provide materials capable of dechlorinating, debrominating, and deiodinating a wide variety of halogenated organic molecules dissolved initially in a highly polar medium. The methodology involves diffusion of the organic molecules into the polysiloxane matrix, their reaction with the embedded iron nanoparticles, and then diffusion of the dehalogenated products back into the polar medium or into the air. Thus, the abilities of the coated particles, as suspensions or within an amino-substituted polysiloxane matrix crosslinked with succinic acid, to dehalogenate various organic molecules (especially the model compounds, bromobenzene and chlorobenzene), have been assessed. Data from several spectroscopic methods demonstrate that the particles are in a crystalline α-Fe phase surrounded by the diacid shell. The effect of embedding 10 wt.% of the particles in amino-substituted polysiloxane-diacid matrices with different COOH/NH2 group ratios and the viscoelastic properties of the polymeric materials have been investigated as well. Potential uses of these gel-like materials to remove halogenated pollutants from various types of aquifers are mentioned.

Resumo em Inglês:

N-Myristoylation protein is catalyzed by N-myristoyltransferase (NMT), an essential target in Leishmania donovani, the causative agent of kala-azar. Four-dimensional quantitative structure-activity relationship (4D-QSAR) analysis was applied to a series of 77 Leishmania donovani NMT inhibitors. Then, three new compounds were proposed using QSAR models. In addition, molecular docking was performed to predict the binding affinities and interaction modes among the proposed compounds and the NMT active site. In silico absorption, distribution, metabolism and excretion (ADME) evaluation was performed and potential inhibitors demonstrated satisfactory pharmacokinetic properties.

Resumo em Inglês:

Both Shuang-Huang-Lian and Xue-Bi-Jing injections are clinically proven efficient and low cost medicines. However, the studies of their chromatographic separation are limited. In this study, a column based on ionic liquid stationary phase was applied for the first time for the analysis of these two injections. For Shuang-Huang-Lian injection, U-shaped plots of retention factors vs. mobile phase constitutions were obtained. This unique kind of separation behavior allowed a flexible adjustment of retention by tuning the mobile phase constituents. Then acids group was analyzed with hydrophilic chromatography mode, while glycosides group was analyzed with reversed phase chromatography mode. Similarly, constituents in Xue-Bi-Jing injection were analyzed with mixed mode high performance liquid chromatography (HPLC). Higher, medium and lower polarity groups were analyzed with hydrophilic interaction, reversed phase and normal phase liquid chromatography modes, respectively. Results from this work provided valuable information for the separation of complicated systems such as traditional Chinese medicine injections.

Resumo em Inglês:

The high Si and Al contents in the amorphous phase of coal fly ash have been used for its conversion into zeolites. This process converts a toxic low-value by-product into a product used in a number of environmental applications, but has the disadvantage of introducing contaminants. Despite the large number of studies on the conversion of fly ash into zeolites, few report this drawback or discuss the efficiency of the proposed processes from a technical or ecological perspective. In this respect, the present study conducts a detailed assessment of two routes for integrated hydrothermal synthesis of zeolites 4A and Na-P1 obtained from coal fly ash. The processes are evaluated and compared in relation to the presence of undesirable metals and elements in the different steps of synthesis, as well as the feedstock and final product. Different performance parameters are presented and applied in the assessment of both processes and the most sustainable is recommended.

Resumo em Inglês:

A cigarette brand automatic classification method using near-infrared (NIR) spectroscopy and sparse representation classification (SRC) algorithm is put forward by the paper. Comparing with the traditional methods, it is more robust to redundancy because it uses non-negative least squares (NNLS) sparse coding instead of principal component analysis (PCA) for dimensionality reduction of the spectral data. The effectiveness of SRC algorithm is compared with PCA-linear discriminant analysis (LDA) and PCA-particle swarm optimization-support vector machine (PSO-SVM) algorithms. The results show that the classification accuracy of the proposed method is higher and is much more efficient.

Resumo em Inglês:

A one-pot synthesized persimmon tannin (PT)-based novel biosorbent modified with 2,5-dimercapto-1,3,4-thiadiazole (DMTD) was prepared for the selective adsorption of AuIII from aqueous mixtures. The synthesized biosorbent was designated as DMTD-PT and characterized using elemental analysis, zeta potential, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The batch adsorption experiments in a model electronic waste leachate revealed that both DMTD-PT and PT had poor affinity for coexisting base metal ions, however, DMTD-PT and PT adsorbed 97.7 and 32.7%, respectively, of AuIII with an initial AuIII concentration of 78.0 mg L-1 in the mixtures with a dosage of 2.5 g L-1 each at pH 3.0 at ambient temperature. The adsorption results indicate the superior selectivity of DMTD-PT for AuIII compared to that of PT. The continuous column experiments further proved that DMTD-PT can be used to separate AuIII from aqueous mixtures. The maximum adsorption capacity of DMTD-PT for AuIII was determined to be 0.42 mmol g-1. A kinetic study in combination with XPS and FTIR analyses of fresh and spent DMTD-PT further revealed that the potential biosorption mechanism can be attributed to the collaboration of electrostatic interactions and coordination.

Resumo em Inglês:

A general method was developed for studying the diversity of individuals in a population based on the diversity of infrared spectra of solid cyanuric acid analytes obtained from various reactions of trichlorocyanuric acid. This method first generates infrared bar spectra for the analytes and then measures the coincidence and continence among pairs of the spectral peaks via confrontation matrices. Class markers are established to characterize analyte classes. Possible correlations among the employed reaction conditions and the nature of the produced solids, which are based on their infrared bar spectra, are discussed. The method of coincidence may be useful for characterizing polymorphs, particularly those of active pharmaceutical ingredients (APIs). The method may also be extended to define the homogeneity of solid analytes. The ANALIN module of the ANALOR software suite running on a dBase platform is used to generate the bar infrared spectra and to handle all calculations.

Resumo em Inglês:

The effects of structure and composition of different montmorillonites on their catalytic performance in the dimerization of unsaturated fatty acids were investigated. The dimerization reaction was performed at 240 ºC for 3 h, with montmorillonite as catalyst, and LiCl as the co-catalyst. The results showed that the specific surface areas of the different montmorillonites did not have a major effect on their catalytic performance, but the interlayer spacing and surface acidity of montmorillonite show significant effects on the product yield. After the organic modification through hexadecyl trimethyl ammonium bromide (CTAB) intercalation, the microenvironment of the montmorillonite layer changes. Moreover, the inner and outer surfaces change from being hydrophilic to lipophilic, which improves the dispersibility of montmorillonite in fatty acids. The xAl/xSi molar ratios of the three samples are similar and lie within the range of 0.4306-0.5010, thus the xAl/xSi molar ratio has little effect on the dimerization reaction.

Resumo em Inglês:

Photocatalytic reactions to convert CO2 and H2O into solar fuels using only solar irradiation have been investigated in this work. For this purpose, titanosilicate ETS-10 was decorated with Cu2O and CuO nanoparticles and their properties were analyzed by different techniques. The final materials were applied in photoreduction of CO2 in gas phase under 20 h of solar irradiation. In the final, the products oxygen, acetic acid, formaldehyde and methanol were detected by chromatographic techniques. Photoluminescence and electrochemical studies indicate the interaction between CuxO nanoparticles and Ti-O-Ti-O on the surface of ETS-10, corroborating with the results obtained in the photocatalytic experiments. The best CO2 photoconversion efficiencies into methanol were obtained when using ETS-10/CuxO compared to pure ETS-10. Another important finding in this study is the fact that the reactions were carried out in the gas phase and no scavenge donors were employed.

Resumo em Inglês:

In this work, a method was developed, based on dispersive liquid-liquid microextraction (DLLME) and analysis by ultra-fast liquid chromatography coupled to diode array detector (UFLC-DAD), to simultaneously determine ten antibiotics of two different classes in honey, as well as to evaluate their degradation kinetics in this matrix. The extraction was optimized by a Box-Behnken design and the method provided good linearity and precision, limits of detection (LODs) in the range of 3.1-6.8 µg kg-1 and recoveries between 82.9 and 105.7%. The decay velocities along the storage period have followed a first order model for nine antibiotics, while one has fitted a zero order model. In the analysis of 33 samples, sulfadimethoxine and tetracycline were found in four samples of the same year and type of blooming, freshly produced in different places, at concentrations, respectively, below and 79% higher than the established by the Brazilian legislation. This suggests an application of those drugs to the beehives, probably shortly before the samples were taken.

Resumo em Inglês:

The interaction between four antiparasitic drugs (benznidazole (BZL), metronidazole (MTZ), nifurtimox (NFX) and megazol (MZ)) with human serum albumin (HSA), the main vehicle of biodistribution of xenobiotics, hydrophobic, small and endogenous molecules in the bloodstream, was evaluated by multiple spectroscopic techniques and theoretical calculations. In all cases quenching of the fluorescence of HSA by these drugs involve a static mechanism, due to ground state association. There is just one main binding site in HSA for these four ligands (Sudlow’s site I); binding is spontaneous, moderate, does not have any effect on the polarity around the Tyr and Trp residues and does not perturb significantly the secondary structure of the protein. Molecular docking studies suggest hydrogen bonding and hydrophobic interactions as the main binding forces, i.e., BZL associates with the Trp-214 residue via hydrophobic interactions and with Gln-220, Arg-221 and Glu-449 residues via hydrogen bonding; whereas MTZ associates with Leu-197 and Leu-480 residues via hydrophobic interactions and with Trp-214, Glu-449 and Ser-453 via hydrogen bonding. Furthermore, electrostatic interactions were also suggested for HSA:MZ and HSA:NFX.

Resumo em Inglês:

By rationally introducing aromatic carboxyl functionalized 1,8-naphthalimide, a water soluble fluorescent chemosensor (DA) was successfully synthesized. It could selectively and sensitively detect CN- in pure water via an intramolecular charge transfer to twisted intramolecular charge transfer (ICT-TICT) state change mechanism. The detection limit of the chemosensor DA to CN- was 1.38 × 10−8mol L-1 which was lower than 1.9 µmol L-1 (set by the World Health Organization (WHO)). Notably, DA displayed rapid response (about 1 s) for recognizing CN- in pure water. Furthermore, DA could be applied to monitoring CN- in tap water. Meanwhile, we prepared the test strips based on DA, which could rapidly and efficiently detect CN- in water.

Resumo em Inglês:

This work aimed the development of an analytical procedure using inductively coupled plasma mass spectrometry (ICP-MS) in four modes of operation for simple and fast determination of Al, Ag, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Na, Ni, Pb, Sb, Se, Tl, Hg, V, U, and Zn in fresh and sea water samples attending simultaneously four Brazilian regulations, Ordinance No. 2914, ANVISA No. 274 and CONAMA Nos. 357 and 396. High matrix introduction system enables the introduction of sea water (3.5% m v-1 of NaCl) only 2-fold diluted. Collision cell mode was efficient to overcome polyatomic interferences. The procedure presented limits of detection (LODs) lower than maximum concentrations allowed by regulations. The CRM NIST 1643e and addition-recovery experiments were used to check accuracy and recoveries varied from 84 to 115%. ICP-MS combined with collision cell mode and aerosol dilution led to accurate and simultaneous determinations of 25 elements at different concentration levels in samples containing high contents of total dissolved solids.

Resumo em Inglês:

This study aimed to evaluate the distribution of mercury in rats after controlled chronic exposure to three different doses of HgCl2 for 30 days. Samples of blood, brain, liver, testis, heart, and kidneys were collected for mercury determination. Although the rats were exposed to different doses, the Hg levels in blood were similar among the groups under study. However, the distribution of mercury in the organs have substantially differed between low and high doses. There was a significant tendency to high deposition in the liver and kidney. The deposition profile in the tissues suggests that the level of mercury remains relatively low in blood while it is deposited at preferential sites such as liver and kidney, demonstrating that, at least at the doses studied, the screening for Hg exposure is unreliable by blood sample analysis.

Resumo em Inglês:

Assessment of phosphorus in fruit juices is of great interest due to its essentiality and nutritional properties. This study applied sample treatment strategies to determine phosphorus in fractions of juices. Firstly, total phosphorus (Ptotal) was determined from digestion and sample suspension exploring direct analysis by inductively coupled plasma optical emission spectrometry, which presented no significant difference, for 95% of confidence level. Then, free phosphorus (Pfree) was determined by spectrophotometry and represented 30-90% of Ptotal with an inverse relationship respecting Ptotal concentration. Fractioning according to particle size evidenced highest fraction of Pfree in samples after filtration. Fractioning of phosphorus based on its charge was also performed and the high percentages of P in the anionic fraction (from 91.2 to 95.9%) are related to free inorganic phosphate in equilibrium with its protonated forms. Thus, it is more assailable after consumption, giving this food great functionality on human diet.