Resumo em Inglês:

The perspective is that the energy demand will grow in the coming decades worldwide. The search for renewable energy sources is urgent and necessary. Residual biomass may be a promising source of raw material for obtaining bioenergy. Thus, this research sought to evaluate the energetic and physicochemical properties of residues from the seeds of Brazilian pine (Araucaria angustifolia (Bert.) O. Ktze). The chemical analysis included the extractive, holocellulose, and Klason lignin contents. The residues were pyrolyzed according to the final temperature of each process (300 ºC - 550 ºC) and a control treatment. The proximate analysis was performed to determine the moisture content, volatile matter, ash, and fixed carbon. We determined bulk density, the higher heating value, and the net heating value. The determination of the energetic density was also calculated. The residues showed significant values in lignin and extractives. The pyrolysis treatments performed at the final temperature of 350 ºC and 400 ºC presented a higher value of gravimetric charcoal yield. The charcoal obtained at 500 ºC and 550 ºC had better energetic properties. The Brazilian pine seed residues under the pyrolysis process presented desirable energy characteristics, showing its potential for use as a raw material in bioenergy generation.

Resumo em Inglês:

Melipona subnitida (“jandaíra”) is a species of stingless bee endemic to the Caatinga, a dry forest in the northeastern Brazilian semi-arid. Propolis is a product containing beeswax and plant resin. It contains compounds that can be able to prevent health problems by protecting cells against damage by oxidative agents. M. subnitida produces geopropolis, a mixture of propolis with soil. Samples of geopropolis of M. subnitida, one of inside and another outside of the nest from a hive in the municipality of Mossoró (northeastern Brazil) were analyzed by HPLC-PDA-ESI-MS/MS and their antioxidant activity evaluated by the DPPH and β-carotene/linoleic acid methods. Both samples exhibited similar chemical profile, characterized by 26 phenolic compounds, however, the compounds detected were more abundant in sample collected from inside of the nest. They were tentatively characterized as galloyl hexoses, coumaroyl-O-galloyl-hexoses, cinnamoyl-O-galloyl-hexoses, coumaroyl- and cinnamoyl- galloyl hexoses, phenylpropanoyl-O-benzoyl hexoses, flavanones and ellagitannins. Flavonoids, galloyl hexoses, coumaroyl-O-galloyl-hexosides, cinnamoyl-O-galloyl-hexosides and coumaroyl-cinnamoyl-galloyl hexosides were reported previously in this genus, however ellagitannins and phenylpropanoyl-O-benzoyl hexoses are reported for the first time. Comparing the antioxidant activity of the geopropolis samples from inside and outside of the nest, the latter was higher than the former.

Resumo em Português:

COVID-19 is currently the most critical disease in the world. Thus, several tools have been used in the last two years to contain the spread of SARS-CoV-2. In this perspective, Wastewater-Based Epidemiology (WBE) provides valuable data by including symptomatic, pre-symptomatic, and asymptomatic individuals and anticipating clinical cases. For 37 weeks, the SARS-CoV-2 viral load was monitored in sanitary sewage samples from Goiânia-Brazil. Through pre-concentration, extraction, and purification of viral RNA, followed by RT-qPCR, it was detected in 83.78% (31/37) of the weeks the presence of fragments of the genetic material SARS-CoV-2 with viral loads ranging from 105 to 108 genome copies L-1. The viral load in the wastewater samples was related to the clinical data of the municipality, demonstrating its ability to promote an Early Warning System (EWS). In early 2022, it was possible to predict the increase in clinical cases 3 weeks in advance and issue an alert note to the health authorities. Prevalence estimates ranged from 0.003 to 0.5% and showed good agreement with observed values. Thus, monitoring effluents become another essential tool that can help combat the pandemic’s advance, especially in countries with scarce resources.

Resumo em Inglês:

Anthropic activities are responsible for the increase in environmental contamination, especially in aquatic systems, demanding studies to assess and monitor contamination levels in different water bodies. We have done a chemical characterization of eleven sediments in order to evaluate the level of contamination by domestic sewage from the Capibaribe River, between the cities of Santa Cruz do Capibaribe and Toritama in the state of Pernambuco, Brazil. The classical analyses were performed, as well as the determination of sterol biomarkers using liquid chromatography coupled to tandem mass spectrometry. Sterol ratios corroborated the presence of fecal-derived organic matter, mainly in the sediments collected in regions of higher population occupation. The multivariate statistical analysis clearly showed the regions from the most contaminated to the least contaminated, indicating the severe contamination by domestic sewage in the region. To the best of our knowledge, this is the first study to assess anthropic contamination of the Capibaribe River by using sterol biomarkers and classical analyses in an integrative data interpretation. This can be helpful when making decisions about preventive and corrective actions for human health concerns.

Resumo em Inglês:

Magnetic zirconium-iron oxide nanoparticles loaded on palygorskite as a low-cost adsorbent was produced by one-step co precipitation technique and its properties for phosphate adsorption were overall investigated. The Brunauer Emmett Teller (BET) specific surface area analysis, scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the adsorbent and evaluate the adsorption interactions. The influences of pH, ionic strength and coexisting ions on phosphate adsorption were measured with a discussion of the adsorption mechanism. Results indicated that no very noticeable changes on the surface properties, structure and phosphate adsorption capacity be found for the magnetic zirconium-iron oxide nanoparticles loaded on palygorskite or not. The adsorption kinetics fitted to the pseudo-second-order model and adsorption isotherm followed Langmuir equation and Dubinin-Radushkevich equation. The phosphate adsorption was slightly affected by ionic strength and highly dependent on pH, i.e. increasing pH sharply restrained adsorption under neutral and alkaline conditions. The surface OH groups in the adsorbent processed an important role in adsorption and the adsorption mechanism conformed to ion exchange and complex. The adsorbent could be conveniently regenerated and effectively reused.

Resumo em Português:

The aim of this study was to evaluate the influence of Inca muña phenolic antioxidants in the reduction of acrylamide (AA) in potato chips. The potatoes were cut into 2 mm thick slices, the addition of antioxidants was evaluated by immersion at atmospheric pressure and by vacuum impregnation (VI) at 80 kPa for 10 min. In both cases, two antioxidant concentrations were used (1 and 2 mg Gallic acid equivalents (GAE) mL-1) and times of 15, 30, 60 and 120 s. The greatest reduction of AA was obtained by VI with 1 mg GAE mL-1 for 120 s (67.4%) and 2 mg GAE mL-1 for 15 s (59.3%); while immersion at atmospheric pressure with 2 mg GAE mL-1 for 30 s and 60 s resulted in reductions of 50.8 and 50.9%, respectively. Besides, the addition of phenolics from Inca muña had no influence on the colour of potato chips. VI treatment resulted in increased amounts of phenolic compounds and antioxidant capacity in the potato chips being the most abundant phenolic compounds hesperidin and luteolin glucoside; while in the control samples phenolic corresponded to chlorogenic acid isomers.

Resumo em Inglês:

The pandemic caused by the new coronavirus has resulted in a global health emergency and has prompted an urgent need for new treatment strategies. No target-specific drugs are currently available for SARS-CoV-2, but new drug candidates targeting the viral replication cycle are being explored. A prime target of drug-discovery efforts is the SARS-CoV-2 main protease (Mpro). In this work, we identified a potential inhibitor for SARS-CoV-2 main protease using in silico methodologies. Molecular docking and molecular dynamics studies were carried out to ascertain the inhibitory action of α and β anomers of Punicalagin from fruit peel of Punica granatum against the Mpro protease. The molecular dynamics results revealed that the β-anomeric configuration of punicalagin allowed access to more hydrogen bonds and hydrophobic interaction leading to higher selectivity and specificity of β-anomer than α-anomer. Therefore, the β-anomer of Punicalagin could act as potential inhibitor against the main protease of SARS-CoV-2 and may act as a potential drug candidate.

Resumo em Inglês:

Formaldehyde (FA) is a carbonyl compound, ubiquitous in the environment and among the most widespread pollutants: it has exhibited toxic properties and is classified as a human carcinogen. FA is released from several sources, both temporary (e.g., combustion processes) and permanent (e.g., building products). This work proposes an innovative fully-automated application of headspace solid-phase microextraction (SPME) with on-fiber derivatization for the analysis of airborne FA emitted from liquid solutions or solid manufacts, in static mode, via gas chromatography-mass spectrometry. The method was tested in a wide range of airborne FA concentrations, using SPME and SPME Arrow fibers: the inter-day LOD and LOQ for SPME and SPME Arrow were evaluated, resulting in 0.072 and 0.215 ppm and 0.014 and 0.042 ppm, respectively. Moreover, other conventional detectors, such as Electron Capture Detector (ECD), Thermoionic Specific Detector (TSD), Photoionization Detector (PID), and Flame Ionization Detector (FID), were tested to set an analytical method to meet different requirements. The sensitivity and linearity of PID, FID and MS were comparable, while TSD and ECD were not suitable for the developed method, due to issues of response or linearity. MS results to be the most suitable and perfoming detector, however PID and FID result to be cheaper valid alternatives.

Resumo em Inglês:

As olive oil (OO) is more expensive than other vegetable oils, it is usually adulterated by blending it with more economic edible oils such as cottonseed oil (CSO), canola oil (CO), and soybean oil (SO). This research aimed to determine the fatty acid compositions obtained as a result of blending different proportions of CSO, CO and SO with OO using a gas chromatograph and to reveal OO adulteration by evaluating the obtained data with different machine learning algorithms. The assessment of the OO consisted of two stages. The first step was extraction of the feature vector, while second step was the classification of feature vectors with regard to the data and computing the regression values. Features were extracted using the Relief method, classified with the Support Vector Machine (SVM) and the k-Nearest Neighbor (k-NN) and Decision Tree (DT) algorithms, and the neural network algorithm was used for regression. The highest accuracy values for classification were calculated as 0.946, 0.964 and 0.982 for OO-CO, OO-SO, and OO-CSO mixtures, using the SVM method, respectively. The errors in the regression analysis were computed as 0.005, 0.005 and 0.002 respectively using the neural network algorithm.

Resumo em Português:

In this work, three methods for pattern recognition, used as exploratory data analysis, are revisited. A brief review of principal component analysis, PCA, an unsupervised method, is provided. Next, the Mahalanobis distance and the confidence ellipses usually drawn around the scores samples are discussed. Fisher’s canonical variate analysis (a supervised methodology) is the second method revisited in this work. The third exploratory data analysis methodology addressed is ANOVA-PCA, which uses the analysis of variance to separate variations into main effects, interaction and noise followed by principal component analysis. Unlike the other two, ANOVA-PCA was proposed recently and is still not yet explored in all its capabilities. One advantage of this method is the possibility to calculate the variance of each of the effects involved in the experimental design. The mathematical bases of the three methods are discussed as well as examples are presented.

Resumo em Português:

Instrumental advances have been employed in the study of archeological remains such as prehistoric rupestrians paintings with the objective of chemically characterizing them in order to reconstruct the cultural technologies of a prehistoric human group and/or to support conservation science studies. The analytical techniques most commonly used in archaeometric research are non-destructive or semi-destructive and preferably portable to preserve the integrity of the rupestrians paintings. They include X-ray Fluorescence Spectrometry (XRF), Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM/EDS), Raman spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Laser-induced Breakdown Spectroscopy (LIBS), and the many techniques with emerging applications such as Mössbauer Spectroscopy, X-ray Absorption Near Edge Structures (XANES), Particle Induced X-ray Emission Spectrometry (PIXE) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP-MS). Therefore, this paper presents a review of the literature on the development of chemical strategies employed in the study of rock art, focusing mainly on the critical evaluation of analytical techniques used, limitations, challenges and the perspectives within this area of study.

Resumo em Português:

We developed a UPLC-MS/MS method for the quantification of the ethanol metabolites ethyl-glucuronide (EtG) and ethyl-sulfate (EtS) in blood samples. Sample preparation was a protein precipitation with acetonitrile 0.1% formic acid containing internal standards (IS) 0.5 µg mL-1 EtG-D5 and EtS-D5. Chromatographic separation was performed in a fluoro-phenyl column, mobile phases were 0.1% formic acid in water (A) and acetonitrile (B) in gradient elution from 5% B to 70% B, with 10 min run time. Ionization was performed with electrospray source at 550 °C in negative mode, quantification mass transitions of m/z EtG 221- 75, EtS 125- 80.1, EtS-D5 130- 79.9, and EtG-D5 226- 75.1. The method was linear from 0.1 to 18 µg mL-1 for EtG and 0.02 to 6 µg mL-1 for EtS, specific, with no interfering peaks during the blank samples analyses. The method was precise and accurate, the matrix effect was compensated with the IS (-12% a + 6.1%). EtG and EtS were analyzed in 28 blood samples from trauma patients with positive alcoholaemia. The concentrations of EtG and EtS ranged from 0.25 to 14.11 µg mL-1 and 0.13 to 5.53 µg mL-1, with high correlation with ethanol concentrations, r=0.739 and r=0.817 (p <0,001), respectively.

Resumo em Inglês:

In this work, self-made laboratory centrifuge equipment was developed for the separation of suspensions and immiscible liquids. This centrifuge was based on the Arduino microcontroller and fabricated from simple and recycled mechanical and electronic parts, spending an inexpensive budget suitably. The centrifuge frame and rotors were manufactured of Polylactic Acid (PLA) filaments, which were printed in a 3D printer. Two rotors labeled R50 and R15 were designed and fabricated to use tubes of 50 mL and 15 mL, respectively. The maximum speed reached, without vibration interferences, was 3350 and 3030 rpm for R50 and R15 rotors, respectively. The total fabrication cost of the fabricated centrifuge was less than 100 USD and the assembly process was not complicated. Finally, the centrifuge performance was evaluated through phases of separation of precipitate of CuCO3(s) and clinical blood samples. The obtained results showed achievement in components separation, entirely comparable with those obtained employing a commercial centrifuge.

Resumo em Português:

This research, whit the design and implementation of contextualized laboratory activities in chemistry was carried out, in order to demonstrate the level of argumentation presented by teachers in initial training, first semester of the Bachelor of Natural Sciences program and Environmental Education of the Pedagogical and Technological University of Colombia “UPTC”. This research was developed with a qualitative, interpretive and phenomenological research approach, allowing us to observe the progress presented by the students under study, in terms of argumentative processes, taking as reference Toulmin who describes different levels of argumentation. The research was carried out in three phases: a diagnostic phase that allowed identifying the initial state of the teachers in training, a second phase of design and implementation of the sequence of activities based on situations of context, and finally a third evaluation phase in which the levels of argumentation reached by the students, having as a fundamental basis the triangulation of data between the experiences of the students confronted with theoretical references that would allow us to account for the results found. It was possible to identify the difficulty that students present when preparing structured arguments as proposed by Toulmin, demonstrating the lack of appropriation of scientific language that students have and the low development of this competence at the different levels of academic. Is important to promote the use of different didactic strategies such as experimentation in the classroom, which allow strengthening the different argumentation processes in students.

Resumo em Inglês:

The covalent bond is a classical topic in science education because it is fundamental to a considerable number of other concepts and by its ability to interpret several chemical phenomena. However, the process of learning this concept presents some difficulties discussed here. This article brings together the conceptions related to the covalent bond, identified, and reported from other studies, to find similarities and to organize what is known about the topic in epistemological themes. In this paper, it was conducted a systematic review using 3 databases, reaching more than 200 reports, and classified 253 sentences of misconceptions in 7 epistemological themes. The main contribution of this article is the classification of misconceptions into themes, which enables teachers and researchers to easily identify a topic considering its complexity. This review shows different misconceptions over the same topic, how misinterpretations can appear over all the models and theories related to the covalent bond, heterogeneity of school levels with the same misconception and mixing of theoretical foundations. Finally, we claim that the knowledge of this wide sight can be especially important to further lesson/unity planning, studies, and understanding of how to make a better transition between one topic to another.

Resumo em Português:

In this paper, theoretical and experimental research on blackbody thermal radiation is discussed and historically ordered. The main thermal radiation equations following Planck’s revolutionary idea are obtained using the formalism of statistical mechanics. These equations, already well known, are deduced in a very detailed and didactic way in order to facilitate the reader’s understanding. The consequent results of Planck’s formula for blackbody radiation are analyzed: the limits of the average energy for frequencies tending to zero and infinity, Stefan’s law and Wien’s displacement law.

Resumo em Português:

The interest of researchers in understanding the stage of development of specific areas of knowledge is a way to understand their scientific maturity and their capacity for consolidation. This “popularization” of the knowledge of researchers working in a specific area of knowledge also allows a greater ability to recognize where science is produced and which actors participate in this effort from a series of evaluation parameters, indicative of the productivity of researchers through the number of articles published and the consistency of production and its relationship with the impact of this in the scientific community through citations of articles. Chemometrics, a science that relates measurements obtained in chemical systems or processes through the application of statistical and mathematical methods, an area created 50 years ago, still does not have a study evaluating the evolution of the area in qualitative and quantitative terms. In this sense, this article aims to present data from the profile of Brazilian scientific production in Chemometrics, as well as the training of human resources, in its scientometric aspects to allow an understanding of the dynamics and contemporary reality of the area. In terms of national scientific production is growing proportionally faster than the rest of the world, placing Brazil among the leading producers of knowledge in the area. Researchers in Chemometrics working in Brazil not only publish a significant number of articles, but these publications have a large number of citations, in addition to the training of human resources spread throughout Brazil, distributed among most graduate courses in chemistry, but not restricted to this area. Finally, the area of Chemometrics, which is about fifty years old, is mature, with numbers of publications and training of human resources, but it is noted that a plateau has not been reached in these two numbers, because the critical mass of researchers working in the area is still increasing.