Resumo em Inglês:

For many years, the goal of transitioning from conventional to renewable fuels (bioethanol and biodiesel) has been encouraged by government entities. However, due to the hygroscopicity of ethanol, ethanol/biodiesel blends can accelerate corrosion in metallurgy. Therefore, inhibitors can be added to mitigate corrosion. This research studied the effect of adding ethanol to diesel/biodiesel blends and measured the rate of corrosion on various metals (aluminum, copper, and 304 stainless steel) by the electrochemical impedance spectroscopy (EIS) method. The results indicated the corrosion rate increased with increasing the percentage of ethanol in the blends, and the corrosion inhibition efficiency of tert-butylhydroquinone (TBHQ) decreased upon the addition of ethanol. TBHQ was most effective as a corrosion inhibitor in the B15E5 blend. The inhibition efficiency of TBHQ decrease with the increase of the temperature. The adsorption process and the electrochemical parameters were calculated and discussed.

Resumo em Português:

In the criminal sphere, it is extremely important to identify perpetrators of crimes based on latent fingerprints (invisible to the naked eye) revealed at crime scenes and their corresponding objects. The present work aimed to evaluate four synthetic analogues of curcumin as possible IDL developers, and to compare their results with those of carbon black developer, as well as to reach the most adequate parameters in the use of the LTQ and FT-ICR mass spectrometers with the paper spray ionization (PS) source to study the chemical composition of the endogenous substances contained in the IDL. For this, a 24-1 factorial design was developed, where it was verified that the distance and voltage factors were the most influential for the increase in the response of signals, in the analysis of latent fingerprints by PS. Among the detected substances we can mention around 20 fatty acids, and squalene. Finally, four potential developers, synthetic analogues of curcumin, were compared with carbon black developer. The revelation of latent fingerprints occurred efficiently, allowing the visualization of minutiae, such as bifurcation and end of line, making it possible to classify them, according to the Vucetich Fingerprint Classification System.

Resumo em Português:

The thermal degradation kinetics of avocado seed biomass (Persea americana) was investigated at the heating rates of 5, 15, 20 and 25 ºC min-1 using thermogravimetric (TGA) and differential thermogravimetric (DTG) analysis techniques in the temperature range from ambient to 780 ºC. Chemical analysis of the avocado seed resulted in: 51.4% cellulose, 42.4% hemicellulose, 20.1% lignin, 2.1% ash, 5.6% extractives. The pyrolysis products were characterized via FTIR, SEM/EDS. The isoconversional methods of Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) have yielded activation energy, Eα, varying from 36-323 kJ mol-1, respectively. The calorific value of biochars produced in the present study in the range of 265 to 475 ºC was 16,17 to 20,24 MJ kg-1, respectively, which are comparable to those reported values in the literature. Analyzing the DTG simultaneously with the addition of thermal energy, it can be seen that low molecular weight compounds represent the first degradation curves, followed by hemicellulose, cellulose and, lignin. The results obtained in the present work indicate that its feasible to prepare biochars with tunable properties from residual avocado seeds using a slow pyrolysis process, adding commercial value and reducing the environmental impact caused by the inadequate disposal of lignocellulosic materials.

Resumo em Inglês:

The variety of vegetables available for plant-based beverage production is associated with a lack of specific regulatory aspects and difficult standardization. The aim of this study was to characterize the physicochemical properties of plant-based beverages (five different sources, three different market brands for each vegetable). The parameters studied were pH, moisture content, acidity, soluble ionic calcium at initial pH and pH 4.3, soluble solids, heat coagulation time (HCT), density, conductivity, surface zeta potential, morphology, polydispersity index, particle size. When comparing the mean values of the results found in the present work with model emulsions and/or plant based beverages produced on a laboratory scale, it can be found that the mean values for pH, moisture, soluble solids, calcium, surface zeta potential, particle size, and polydispersity index were similar to the reported values in the literature, however, acidity, HCT, density, and conductivity were lower than those reported in the literature. The coconut plant-based beverage exhibited the most significant statistical difference as compared to other plant-based beverages, especially in terms of pH, conductivity, particle size, and polydispersity index. This study is a promising aid to regulatory agencies and industries for standardization of nutritional value, production, stability, storage and chemical attributes of these beverages.

Resumo em Inglês:

Natural additives with antioxidant properties can be used as biodegradable and sustainable alternatives to synthetic products, because they can inhibit the biodiesel oxidation reaction, increasing oxidative stability and extending its storage period. This research evaluated the efficiency of jabuticaba peels, gabiroba leaves, and hibiscus flowers in ethanolic extracts, analyzing through the simplex-centroid design, the induction periods (IP) and rate constants (k) of the biodiesel oxidation reaction at 110 °C. Antioxidant activity was observed in all extracts, either decreasing k or increasing the IP. The mathematical models obtained showed coefficients of determination greater than 0.9400, a non-significant lack of fit at the 5% level, and low dispersion between predicted and experimental data, indicating that the 1st order reaction fit was appropriate and can be used for predictive purposes. In this work, the optimization was performed with maximization of IP and minimization of k showing that the mixture containing 25% of jabuticaba peels extract and 75% of gabiroba leaves extract was the most suitable, because proportionally increased the IP and decreased k of the biodiesel oxidation reaction. It is possible to suggest the use of jabuticaba peels extract or gabiroba leaves extract as well as various combinations between them as antioxidant additives.

Resumo em Português:

Firearms and ammunition identification produces important information for the elucidation of the crime and also in cases of confirmation of the offender. In a crime scene, when a suspect weapon and its ammunition are found, it is possible to clarify and conclude an investigation using qualitative analysis and standards. However, in some cases only the fragments of ammunition are found, which makes difficult to identify the weapon using traditional techniques. Therefore, alternative methods are needed such as the determination of elemental composition of the lead alloy and the verification of the lead isotopic ratios. The present work includes a review of the basic concepts of ballistics and conventional techniques of ballistic confrontation, the existing studies related to the chemical analysis of ballistic fragments and its application in criminalistics and, finally, the articles involving the lead isotopic analysis as a tool for ballistic identification.

Resumo em Português:

The genus Fridericia belongs to the family Bignoniaceae and comprises 60 species that occur in humid to dry forests, cerrado, and caatinga vegetation. It may be found from Mexico to Argentina and southern Brazil. This article reviews studies conducted on this genus, primarily focusing on its chemical composition and biological activities. Of the 60 known Fridericia species, only 14 have been the object of chemical and biological studies, accounting for 23% of the researched species. Eighty-four compounds, mainly flavonoids, terpenes, xanthones, and phenylethanoids, have been isolated from these species. The biological properties described in this review include antimicrobial, antioxidant, anti-inflammatory, hepatoprotective, antiviral, healing, antiproliferative, trypanocidal, and antileishmania activities. Notably, the species F. chica has been the most studied, as it is listed in the National List of Medicinal Plants of Interest to the Brazilian Unified Health System (RENISUS).

Resumo em Inglês:

Juvenile hormone (JH III) is an important example of a chemical signaling derived from the terpene biosynthetic pathway. Because of its impact on many species’ reproductive and developmental processes, analytical approaches must be developed to accurately identify and measure it in biological samples. In this technical note, we explored the gas-phase dissociative behavior of JH III using tandem mass spectrometry combined with electrospray ionization to provide diagnostic fragment-ions for quantitative purposes.

Resumo em Português:

In organic chemistry, the pKa is a property used to compare the acidity behavior for many substances, and to locate the position of equilibria in acid-base reactions and to provide information about structure and reactivity. Evidence in the literature shows that the values of pKa for water and hydronium ion, commonly cited in organic chemistry textbooks, are incorrect. The values of 15.74 for H2O and -1.74 for H3O+ are due to a propagated misconception in the equilibrium calculations while the correct values are 14.0 for H2O and 0.0 for H3O+. This subtle difference of 1.74 units on the pKa scale between both values reflects an error greater than 55 times in the level of acidity for these chemical species. An immediate correction of these values is necessary for the adequate teaching of organic chemistry. A literature search was conducted on the most used organic chemistry books in graduate and undergraduate courses in Brazil, revealing that almost all values cited were inadequate. The textbook Chemistry of Organic Compounds, 3rd edition (1965), by Carl Robert Noller is suggested as possible source of this misinformation in organic chemistry textbooks.

Resumo em Português:

With clear and objective language, this article invites the reader to reflect on the relationship between autism and Brazilian Chemical Education. Here, we begin with approaches to autism in legal terms, which allow the reader to understand how autistic people and their families have their rights guaranteed by law, especially in the school. We also present the point of view of the teacher who trains the graduate and the one who receives an autistic student in the classroom, with reflections about their training curricula that are imperfect in terms of inclusion, which generates situations of discomfort and frustration in their work. We continue to discuss how inclusive education strategies adopted by professors in the area of chemistry aimed at autistic students have stood out, even in the midst of a scarce bibliographic reference. Finally, we turn our attention to one of the main places where inclusion takes place: the school, with valuable discussions about the role that it has played in the inclusion of the autistic student.