Resumo em Inglês:

This study investigated the feasibility of H2 production by acid corrosion, employing a by-product from the fertilizer industry (Hexafluorsilic acid - H2SiF6) and waste iron sources. Different masses of metal from three different sources: iron powder (waste from metal workshops), steel wool and rebar (construction waste), were reacted with various proportions of H2SiF6 with HCl. The influence of the variables was evaluated by factorial design, verifying greater production of H2 for materials with higher contact areas. The lowest production was observed for construction industry waste (rebar) probably due to the presence of protective films and lower contact area. The gas produced was analyzed by gas chromatography and was found to consist only of H2 (up to 99%) and air. The results indicate a promising application of H2SiF6, which is generated in large quantities during phosphate fertilizer production and has few commercial applications. The method proposed is promising, it does not emit toxic or polluting gases, contributing to the sustainable generation of H2.

Resumo em Inglês:

This work aims to evaluate the possible relations between the confirmed daily cases of COVID-19 and the environmental parameters for the Cuiabá-Várzea Grande conurbation in the state of Mato Grosso, Brazil. The data sets used to cover the rainy-dry periods, from January to December 2020, were achieved from a database of government institutions, and processed through the Spearman correlation test. Our results showed that atmospheric pressure and fire radiative power has a significant positive correlation, suggesting that these parameters favor the transmission of COVID-19. On the other hand, the relative humidity of the air and the total column of water vapor showed a significant negative correlation with the number of confirmed daily cases of COVID-19, which indicates that the water vapor present in the atmosphere acts in the regulation of virus transmission. Thus, taking into account the results obtained, there is a need for collaborative policies and measures among the three spheres of executive power in Brazil, to act in the surveillance of fire cases, which can favor the transmission of COVID-19. In addition, prevention and protection measures aimed at reducing the spread of coronavirus continue to be indispensable.

Resumo em Inglês:

The electrospinning has been widely used in tissue engineering for the preparation of wound dressing with the most varied polymers and drugs. Considering that propolis has antimicrobial and anti-inflammatory characteristics, the aim was to develop electrospun fibers from PBAT (poly (butylene-adipate-co-terephthalate)/PCL (poly(ε-caprolactone) containing propolis in order to promote antimicrobial action and the healing of wounds. By the optical microscopy analysis, the best parameter for obtaining the fibers was chosen: 16.5% (v/v) of propolis extract alcoholic solution, 14.0 cm needle-collector distance, 17.0 kV of voltage and 0.5 mL h-1 flow rate. The scanning electron microscopy demonstrated fiber diameters of 0.51 ± 0.12 μm for the polymer blend and 1.16 ± 0.98 μm for the blend with propolis. The Fourier transform infrared spectroscopy (FTIR) results showed no evidence of chemical interaction with propolis, this being a physical interaction. This interaction was corroborated by the differential scanning calorimetry (DSC) due to the variation in the heats involved, mainly in the aromatic part of the polymer blend, indicating a better interaction in the PBAT group. Finally, it was found that fibers presents propolis antimicrobial activity against the bacteria Pseudomonas Aeruginosa. The results indicate that this blend has a great potential to be used as a cutaneous dressing.

Resumo em Inglês:

This research was aimed to evaluate the concentration of 15 chemical elements as a reference base for the quality of the litter in a forest in the central region of the Amazon. The sampling of the litter was performed monthly in two topographic positions for one year. For the quantification of the elements, digestion by nitroperchloric solution and reading by ICP OES were performed. The mean of macronutrient contents in the litter in decreasing order were Ca>K>Mg>Na. For micronutrients, the order was Al>Mn>Fe>Sr>Zn>Cu>Ba>Cr>Ni>Co>Cd for the Plateau and Al>Mn>Fe Sr>Zn>Cu>Ba>Cr>Ni>Cd>Co for the Baixio. Among the fractions, calcium had its highest concentration in the woody material, potassium in the reproductive material, while magnesium, sodium, and aluminum showed higher concentrations in the leaf fraction. Also, it was observed that the return of the elements to the soil by litter was greater in the dry period of the region, due to the greater fall in plant material. Calcium differed significantly within the same area, obtaining the highest concentrations compared to the other elements, while aluminum and zinc differed significantly between the areas studied, with a higher return for both elements on the Plateau.

Resumo em Inglês:

The lanthanide complexes [Ln(bmdm)3(L)] where Ln(III) = Eu and Sm were synthesized successfully using the diketone (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl) propane-1,3-dione) (bmdm) and (L) = 1,10-phenanthroline (phen), 2,2’-bipyridine (bipy) ligands. The coordination modes were determined as bidentate chelate by the FT-IR. The ground state geometry was determined using the Sparkle/AM1 implemented in MOPAC2016 package. Europium complexes exhibit the characteristic emission bands that arise from5D0→7FJ (J = 0-4); the presence of just one5D0→7F0 line transition means that this site is without the center of inversion. Samarium complexes display transitions at4G5/2→6HJ (J = 5/2; 7/2; 9/2 and 11/2), being the4G5/2→6H9/2 the most intense, indicating that the forced electric dipole mechanism is predominant when compared with the magnetic dipole ones. The intensity parameters Ω2 and Ω4 were calculated according to the emission spectra for Eu(III) and absorption spectra for Sm(III). The high Ω2 values demonstrated that the lanthanide ion in bipy or phen complexes is in a highly polarizable chemical environment. The emission lifetime (τ) increases compared with that of precursor aquo complexes, confirming that the non-radiative quenching is minimized. The low quantum efficiency is a result of NIR emissions and non-radiative transitions of Sm(III).

Resumo em Inglês:

It is herein described the synthesis of a series of thirty novel 1,2,3-triazole-1,4 disubstituted compounds inspired on the known SRPKs inhibitor N-(2-(piperidin-1-yl)-5-(trifluoromethyl)phenyl)isonicotinamide (SRPIN340) and biological evaluation of them against human glioblastoma multiforme cell line U87MG. Starting with 1-fluoro-2 nitro-4-(trifluoromethyl)benzene (1), the substances were prepared via a five-step synthetic route. The crucial step corresponded to the copper-catalyzed cycloaddition reaction between trifluoromethyl phenyl azides and different alkynes. In general, the compounds were obtained with good yields and they were characterized utilizing spectroscopic (IR and NMR) and spectrometric (HRMS) techniques. The evaluation of the synthesized compounds at three different treatment time (24 h, 48 h, and 72 h) and concentrations (50, 100, and 150 µmol L-1) revealed that five derivatives were capable of reducing cell viability by 50% after 72 h of treatment at the highest concentration. On the contrary, three derivatives significantly increased cell viability being this effect more pronounced after 48 h of treatment. In this regard, it stands out the compound 2-((1-(2-morpholino-5-(trifluoromethyl)phenyl)-1H-1,2,3-triazol-4-yl)methyl)isoindoline-1,3-dione (7) which increased cell viability in approximately 300% after 48 h of treatment at 100 µmol L-1. The substances that increased cell viaiblity present as common structural features the presence of a saturated nitrogen-containing six-membered ring and carbonylated fragments.

Resumo em Inglês:

Certainly, most chemistry students, patients or simply curious, have already questioned themselves about certain medications present in their daily lives, trying to understand how they work and even how they can be obtained. Based on that, this work presents some known synthetic routes and the structure-activity relationship (SAR), of some active pharmaceutical ingredients present in medications distributed in Brazil by the government program known as “Farmacia Popular”, emphasizing the functional groups and chemical structure linked to their mechanisms of action. Some other characteristics and future perspectives of such drugs and their respective active principles are also highlighted.

Resumo em Inglês:

Levulinic acid is a reactive polar organic compound deemed as a building block for several products with relevant applications, replacing traditional substances in the petrochemical industry. Considered a platform molecule, levulinic acid is industrially produced from the acid hydrolysis of biomass - mainly plant-based - using hydrochloric or sulfuric acid in homogenous catalysis. However, considering the World Market for levulinic acid is expected to reach US$ 71.9 million in 2027, growing annually at 14.1%, and its applications in agriculture, pharmaceuticals, plasticizers, cosmetics, and food additives, the development of alternative production processes is sought. Hence, a survey was performed on publications considering the alternatives for biomass-based levulinic acid production processes: I) alternative homogenous catalysts to avoid using noble materials in the reactor; II) heterogeneous catalysis to facilitate and reduce the catalyst’s separation and recovery costs; III) ionic liquids, exploiting their high solvency, stability, and catalytic capacity. Additionally, biomass alternatives for obtaining levulinic acid are presented, showing that other agricultural residues and animal biomass options are being considered, targeting process flexibilization while reducing costs and producing derivatives at more competitive prices. Thus, it can be stated that levulinic acid is an important platform molecule for biorefineries’ economics, replacing fossil fuels with renewable raw materials.

Resumo em Português:

Biomaterials have been intensively investigated due to the increase in the elderly population and high prevalence of several disorders, such as cardiovascular and orthopedic diseases. Polymeric and composite polymeric materials in combination with different processing techniques, such as electrospinning, solution blow spinning, ultrathin film preparation, and 3D printing are promising for obtaining biomaterials with patient-specific applications. Here, we provide a review on recent advances and perspectives for synthetic and natural polymers as well as composites in the design of biomaterials. After introducing basic information about biomaterials, we describe the fundamentals of manufacturing techniques and highlight possible biomedical applications.

Resumo em Inglês:

Plastic pollution is a major societal, economic, and environmental issue. Upon release into the environment, plastics are altered by biological and physicochemical processes that influence their fate and transport within ecosystems. Large plastic debris can fragment into smaller pieces and are called microplastics (MPs) when occurring at sizes between 1 µm and 5 mm, fragmented or produced in this range. These small pieces of plastics are ubiquitous anthropogenic contaminants found throughout the world; however, the environmental consequences and effects on biota are not clearly understood. Scientific literature on the environmental implications of MP pollution is expanding rapidly and critical review of this literature is necessary to identify areas of evolving consensus and remaining gaps in knowledge. Herein a comprehensive literature review was performed to assess (i) the sources and distribution of MPs in different environmental compartments, (ii) the analytical methods that have been applied worldwide, and the key analytical challenges that remain in assessing MPs in the environment, and, finally, (iii) to integrate the findings of Brazilian MP research, which showed that since 2004 (80 papers up to 2020) has documented the presence of MPs in aquatic matrices and sediments with focus on marine ecosystems, mainly identified by visual inspection.

Resumo em Inglês:

Caffeine and guarana are safe foods according to the American (FDA) and Brazilian (ANVISA) health agencies. However, data regarding the composition, quality, and safety of guarana-based food supplements sold in Brazil are limited. Most of the methods used for quantification of caffeine and other guarana chemical markers are based on complex extraction techniques as well as on gradient elution and do not evaluate the matrix effect nor the uncertainty estimation measurement. A simple and selective method for caffeine detection has been developed and validated using HPLC-UV. It shows linearity between 1 and 10 µg mL-1, has a significant matrix effect (p < 0.05) and its expanded uncertainty varies from 6.9 to 16.7%. Other parameters (selectivity, recovery, precision, robustness, limits of detection, and quantification) were satisfactory. The present study has analyzed 30 commercial samples of guarana-based food supplements (powders and capsules). Powder samples have shown an average caffeine level of 25.27 ± 5.20 mg g-1 while capsules 28.53 ± 13.81 mg g-1. No significant difference between the two types of samples has been observed (p > 0.005).

Resumo em Inglês:

This work proposes a novel approach for colorimetric assays using ubiquitous and inexpensive water beads (WBs) made of a superabsorbent polymer (sodium polyacrylate). The high-water absorption capacity by the WBs was exploited for the preconcentration of iron ions from samples of tap, well, and lake waters. Moreover, the WBs also worked as a substrate for colorimetric detection of iron by the classical reaction of formation of Fe(II)-phenanthroline complex. Digital images acquired with a smartphone were used to obtain the color intensity of the WBs containing the orange color complex. The WBs were able to uptake and preconcentrate iron ions, allowing colorimetric detection with good linearity (R2 = 0.9978) and limits of detection (LOD) and quantification (LOQ) of 0.02 and 0.07 mg L-1, respectively. The proposed method provided recoveries ranging from 93 to 111% for a sample of well water spiked with 0.15 mg L-1 of iron.

Resumo em Inglês:

There is a global concern with pollutants and organic contaminants and efficient and inexpensive methods are sought for the treatment of these toxic products. Generally, large volume reactors and the use of expensive equipment are required to monitor a photoreaction. The present work proposes the construction of a colorimetric equipment, which allows the online monitoring of photoreactions, using low-cost materials that allow the analysis from small aliquots. To show the applicability of the system, we studied the reduction reaction of 4-nitrophenol (4NP) with NaBH4. The impedimetric sensor enabled to construct the kinetic curve of the decrease in the chromophore band. It was possible to observe that the 4NP reduction reaction depends on: (i) chromophore concentration; (ii) stability of the reducing agent and; (iii) repulsion between the anions. The system developed here opens doors, as it can be used using a photocatalyst in the form of film, and it has also proved to be an inexpensive alternative for both research and teaching laboratories, as it allows the execution of chemical physics practices such as kinetic monitoring of reactions and mathematical adjustment of the curves.

Resumo em Português:

This work presents an analytical framework focusing on the evaluation of contributions of formative actions to teaching practice. It consists of thirteen indicators, distributed into four levels, The framework was developed from analyzing participants’ final assignment, who attended a Specialization Course in Teaching Methodology in Natural Sciences, offered in a non-formal education setting. Potentialities and limitations related to the teacher education framework are discussed, as well as its application in the context of teaching chemistry.

Resumo em Espanhol:

This article presents the results of the study of explanatory models produced by 81 students of first-year of medicine at the Universidad del Norte in Barranquilla-Colombia. The students face a case in the area of chemistry applied to medicine, through a contextualized problem situation (SPC), constructed from a perspective of teaching chemistry in context. The explanatory models generated by the students were analyzed qualitatively at four moments of the implementation of a teaching proposal. The results obtained at the beginning of the implementation of the proposal indicate that the students did not elaborate any type of explanatory model. However, these arised from the teaching proposal that involves the SPC in which the students begin to generate explanatory models supported by chemistry content and categorized mostly in the research as Descriptive and Interpretative, a situation fostered by the theoretical and methodological coherence of the SPC, which was designed from a perspective of teaching in context based on modeling and leveraged by scaffolding.

Resumo em Inglês:

In this work, we call the attention to the ambiguity found in the literature when labeling vibrations and molecular orbitals as B1 and B2 for molecules belonging to the C2v point group as, for example, the water molecule. A survey of several books and some articles shows that this ambiguity comes from a long time ago and persists today, being a source of misunderstanding and a waste of time for students and teachers. It means that, in the case of the point groups Cnv, Dn, and Dnh (n = 2, 4, 6), it is very important to draw students’ attention to this ambiguity that exists in the literature. It is unfortunate that the recommendation made by Mulliken, more than sixty years ago, to always place the water molecule in the yz plane, has not been followed.

Resumo em Português:

The metabolomics approach is widespread and accepted in several lines within life sciences. However, much of what has been called metabolomics could be better defined as a comparison study, regardless of its purpose. Metabolomics finds its definition in the understanding of biological properties and effects on a given organism. In any case, the tools used in metabolomics are undoubtfully useful and should be used in natural products studies, both those already established and those that are under development. Natural products research is in a continuous process of evolution to become a discipline driven by multivariate data with a solid influence of “omic” technologies.

Resumo em Português:

Historical aspects related to eight reagents that were present in analytical chemistry laboratories in the first decades of the twentieth century are described. They have peculiarities that are based on their curious names or the purposes for which they were intended. Their presence in the laboratory environment reflected their industrial applications and the chemical analysis procedures used at that time. From the mid XXth century, with the migration of qualitative analysis to the chemistry teaching, these reagents have been replaced by others that today serve the same purposes as those previously used. However, many of them still retain their industrial importance. This historical overview emphasizes the importance of the evolution of chemicals and chemical assays for security and efficiency reasons. Learning from past experiences develops a critical spirit and laboratory behavior more committed to occupational hygiene and safety, without losing sight the learning power that qualitative analytical chemistry offers.