Resumo em Inglês:

Cellulose derivatives still receive special attention in today biomedical applications due to their biocompatibility, ability to form resistant membranes and compatibility with various bioactive agents. In this work, cellulose acetate (CA) was used to prepare membranes with different morphologies aiming to evaluate the release profile of the drug ibuprofen (IBF). The IBF incorporation was performed by the addition of 10% of the drug in an 8% (w/w) CA/acetone solution. The morphology of the membranes was modified by the addition of water, used as porogenic agent. Drug release assays showed the effect of morphology on the cumulative drug release curves. The symmetric membrane exhibited retention of significant amounts of the drug and a slow release process that lasted for more than 50 hours. The asymmetric porous membranes presented different behavior with greater amount of drug released in less time of release. The kinetic parameters calculated from the Higuchi and Korsmeyer/Peppas models indicated release profiles controlled by diffusion/solution process in the polymer matrix. The results revealed that the interactions established between IBF, CA and the matrix morphology are significant factors for the kinetic control of the drug release process and enable to choose different applications of the membranes loaded with IBF.

Resumo em Inglês:

The objective of this paper was to study the effect of pH, concentration and ionic species on the water absorption of the bionanocomposite hydrogels based on carboxymethylcellulose polysaccharide and laponite nanoclay. Bionanocomposite hydrogels were obtained via free radical polymerization. It was possible to observe that the swelling degree (Q) and kinetic properties were strongly influenced, and controlled, by the presence and quantity of ionic species, decreasing their water uptake when compared to the same values obtained in distilled water. Furthermore, the addition of nanoclay decreased the water uptake sensibility of the hydrogel in ionic media. It was also observed that the presence of the nanoclay decreased the Qeq distilled water values from 32.5 g g-1 to 22.5 g g-1. The pKa variation of the bionanocomposites was a good indication of the possible interaction of the nanoclay-polymeric chains. The possibility of the control of water absorption (velocity and quantity) whereas these nanocomposites are pH- and salt-responsive may potentiate their application in agriculture. Agronomical studies are in progress, which can confirm its applicability in this area.

Resumo em Inglês:

The power of a compound is enhanced by the direct connection of nitrogen atoms, and its stability can be improved through conjugated structure. So novel high energy density materials N14 (1,6-dihydro-1,2,3,3a,4,5,5a,6,7,8,8a,9,10,10a-tetradecazapyrene) and N18 (1,2,2a,3,4,4a,5,6,6a,7,8,8a,9,10,10a,11,12a-octadecazacoronene) were designed, and their structures, detonation performance, and stabilities were calculated employing density functional theory (DFT). The detonation performance includes detonation pressure (P), detonation velocity (D), and heat of detonation (Q). Furthermore, the stability involves frontier molecular orbitals and impact sensitivity. Calculations reveal that they have an excellent power, detonation performance of N14 (P = 43.6 GPa, D = 10040 m s-1, Q = 2214 cal g-1) and N18 (P = 37.4 GPa, D = 9400 m s-1, Q = 2114 cal g-1) are comparable to CL-20. Besides, their impact sensitivities are slightly better than CL-20, therefore they are promising candidates in energetic materials.

Resumo em Inglês:

Fingerprints are unique for each individual contributing to human identification in forensic cases. Visualization of latent fingerprints usually involves the use of a chemical substance that creates a contrast between fingerprint residues and the surface on which the print was deposited. Commercial powders used as fingerprint developers by papilloscopy have relatively high costs due to their importation and chemical composition. (E-1,3-diphenylprop-2-en-1-one, E-1-phenyl-3-(4-methylphenyl))prop-2-en-1-one but only one compound was highlighted, E-3-(3-nitrophenyl)-1-phenylprop-2-em-1-one). The composite was selected for its suitable properties (adhesion and texture) of visualization of the digital, providing the obtaining of clear revelations with identification of minutiae and singular points of the fingerprints. Identification, magnetic resonance, granulometry and contact surface evaluation with chalcones such as sebaceous and natural deposition with development in different materials such as plastic, metal and glass were applied for the application of fingerprint development. The compound was tested in eight volunteers regardless of gender and age, presenting satisfactory results for fingerprint development on glass and metal surfaces.

Resumo em Inglês:

This paper discusses the synthesis and resulting catalytic performance of mesoporous alumina using aluminum isopropoxide as the aluminum source, and synthesized organosiloxane KH560-540 as template. The effects of the hydrothermal conditions, as well as the amount of templating agent at pH values of 5-9 on the structure of the synthesized mesoporous alumina were investigated by nitrogen adsorption-desorption methods, XRD and electron microscopy. Alumina from a rod-like scaffold structure was obtained, and the specific surface area was as high as 508 m2 g-1. Also, the coordination state of aluminum before and after calcination was analyzed by 27Al-NMR spectroscopy. The role of the templating agent in the synthesis process was determined. The synthesis mechanism of mesoporous alumina prepared by a KH560-540 template was also proposed. The acidity of samples that were synthesized by different templating agents were compared to NH3-TPD, and the content of Si in each sample was tested by ICP-OES, the results show that the silicon content has little effect on the acidity of the sample. Finally, we used the synthesized mesoporous alumina to catalyze the cyclization of dichloropropanol to epichlorohydrin, which showed excellent catalytic performance:dichlorohydrin conversion is up to 96% and epichlorohydrin yield of nearly 92%.

Resumo em Inglês:

First-generation methods used to quantify HDL-cholesterol have been used for decades. Therefore, first-generation precipitatingreagents still in use, the chemical impact on HDL-particles functionality (structure/activity-relationship) is not well-documented. The study aim was to identify the most efficient precipitating-reagent for lipoprotein separation to be used in the HDL functionalevaluation. A cross-sectional design with convenience sampling was conducted. Plasma samples from 40 individuals, both genders, were evaluated. Biochemical analysis was performed after using different chemical precipitants (e.g. polyethylene glycol - PEG (P1), phosphotungstic-acid (P2), and dextran-sulfate/MgCl2 (P3)) to evaluate HDL-particle-size and PON1-activity. Parametric and non-parametric tests were performed using GraphPad-Prism 5.01 (USA). Differences were considered significant when a p-value < 0.05 were obtained. The PON1-activity comparison differed after NaCl stimulation (p < 0.001, paired t-test) and among chemical precipitant treatments. The PON1-activity differed after sample precipitation with P1 when compared to P2, and P3 (p < 0.05; ANOVA), before and after stratification for dyslipidemia group. The HDL particle-size comparison did not differ, but on the other hand, polydispersity differed after sample precipitation with P3 when compared to P1 or P2 (p < 0.05; ANOVA). Dextran- Sulfate/MgCl2 was a better chemical precipitant for PON1-activity, and PEG for HDL-particle-size, respectively. The HDL functional

Resumo em Inglês:

Foods with high lipid contents are susceptible to deterioration by oxidative processes that lead to the formation of food rancid. Determining the chemical nature of lipid oxidation products presents a nutritional and health interest due to the possibility of formation of compounds related to the development of degenerative diseases such as Parkinson’s and Alzheimer’s. In this context, the present study describes the use of nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA) to monitor the formation of oxidation products in Brazilian table margarines subjected to the heat treatment at 80, 100, 120, 140, 160 and 180 °C. Lipid profiles were characterized by 1H NMR experiments. Changes due to heat treatment were identified by NMR-PCA models, which indicated triacylglycerol (TAG) as the main descriptor from 160 °C. At this temperature, were identified signals evolution in 1H NMR spectra whose chemical shifts (δ) indicated the formation of aldehydes and dienes. The results were useful to highlight the need for efficient methods to maintain the oxidative stability of this type of food widely used in industrial and home cooking.

Resumo em Inglês:

Melissopalynological, physicochemical analysis, mineral content, antiradical activity and profile of compounds by Ultra-Performance Liquid Chromatography coupled with a Diode Array Detector and quadrupole Time of Flight Mass Spectrometry (UPLC-DAD-qTOF-MS/MS) of Frieseomelitta doederleini honeys from semiarid region of the Northeast of Brazil are presented. The melissopalynological analysis showed two principal pollen types of Mimosa tenuiflora (jurema preta) and Shinus sp (aroeira). The chemical profile data obtained by UPLC-DAD-qTOF-MS/MS of the Mimosa tenuiflora flowers (principal pollen of honey) and the five samples of F. doederleini honeys both flowers and honey showed similar profile. Abelha branca honeys samples had similar characteristic profile of phenolic compounds (flavonoids), and also antiradical activity. The main flavonoids identified in the honey samples in the jurema preta flowers were flavonols/flavone and flavanols/flavanones aglycones. All the flavonoids identified showing that the nectar collected by the bees may be from this plant species. The antiradical activity of the honey samples strongly correlated with their phenolic content. Among the minerals analyzed, potassium was the most abundant, followed by magnesium.

Resumo em Inglês:

In this work, density functional theory (DFT) was used to study the caused effect on reactivity of 8-hydroxyquinoline (8-HQ) by substituent groups (-H, -CH3, -OCH3, -Cl and -NO2) on different positions of the 8-HQ structure. DFT was also used to obtain the electronic profile of β-amyloid peptide (Aβ) bind site to Zinc. The energies and absolute hardness (η) values, besides participation percentages values and graphical representation of highest occupied molecular orbital (HOMO) of 8-HQ derivatives and lowest unoccupied molecular orbital (LUMO) of Aβ bind site to Zinc (ZnAβ) were analysed. The calculations indicated that the hardest ligands with each substituent formed the most stable complexes with Zinc, and the electronic nature of substituent points to a preferential position on 8-HQ structure. The LUMO profile of ZnAβ showed that the ligands dislocate one of histidine residues for interacting with Zinc.

Resumo em Inglês:

National industrial effluent remediation strategies are largely outdated, which makes these processes costly and at the same time inefficient. Among the most worrying compounds are heavy metals, which have bioaccumulative and toxic characteristics to living beings. In addition to these, high nutrient loads constitute a huge environmental problem, since the devastation promoted by eutrophic niches is capable of disrupting complex food chains. This paper presents a bibliographical review of the current researches that are applying biomass from microalgae in effluent bioremediation, both domestic and industrial (mainly the latter, since its pollution potential is abruptly greater). Such strategy is interesting since the diversity of these microorganisms is abundant, propitiating the application of them in various conditions. Another point to be taken into consideration is the fact that many species of microalgae produce large amounts of lipids, many of which have potential application in the production of biodiesel.

Resumo em Inglês:

Hops in the brewing process are important for the chemical and sensorial quality of beer. Hops give to the beer bitterness (due to the presence of humulones and lupulones), natural antioxidants (due to the presence of polyphenols) and flavor (due to the presence of volatiles and essential oils). In this paper, we present, for the first time in Portuguese, a critical and comprehensive review about the phytochemistry of hops and the relationship between hop chemistry and the brewing process.

Resumo em Inglês:

Bisphenol A and ethinylestradiol, both considered as endocrine disruptors, have been found in surface water and effluents from municipal wastewater supply and can cause adverse health effects on wildlife species and in human beings at extremely low level. In order to remove these compounds from wastewater, constructed wetlands has been used since it proved to be more efficient, and has less cost than conventional treatments. One of the mechanisms of removal of endocrine disruptors by constructed wetlands is the uptake by macrophytes, so it is necessary to analyze these compounds in the plants of the system. Thus, the objective of this study was to develop and validate two methods by high performance liquid chromatography with fluorescence detector capable of determining these compounds in dwarf papyrus and water hyacinth. The evaluated parameters in the validation were: linearity (R2 ≥ 0.99), limit of detection (LOD = 0.045-0.15 µg g-1), limit of quantification (LOQ = 0.15-1.50 µg g-1), accuracy (recoveries from 83.5 to 119.4%) and precision (intra-day CV ≤ 6.2% and inter-day CV ≤ 5.8%). Samples from a constructed wetland were analyzed and the developed methods showed be suitable for intended purpose.

Resumo em Inglês:

Sweetened condensed milk contains various dispersed particles, such as proteins, fats, and lactose, all of which make it highly viscous. During sweetened condensed milk production, microcrystalline lactose is added in order to control the product crystallization. The purpose of this study was to characterize the behavior of commercially sold sweetened condensed milks submitted to laser particle size analysis using two different dispersion media: water and a lactose solution. The lactose solution dispersion medium extended the length of time the sweeten condensed milk samples’ original characteristics were present during the laser diffraction particle sizing measurements that were carried out. Significant difference was observed (p < 0.05) between analysis times when water was used as a dispersing medium versus when a lactose solution was used (p > 0.05). Using a lactose solution as a dispersion medium when determining particle size in sweetened condensed milk prolongs the original characteristics of the sample substance during laser diffraction particle analysis.

Resumo em Inglês:

The main goal consisted in the characterization of gradual concepts according to the categories of physical and chemical processes. The first step was to identify preceding notions about this principle of interaction in daily happenings, followed by the implementation of didactic interventions in order to appropriate the concept, and, finally, the determination of better acceptance of mental representations. This proposal has promoted the comprehension of the universe at macroscopic and microscopic levels and fosters constructive attitudes towards the study of science. This study is based on the corpuscular theory of matter and its interaction with light as a form of energy. The approach is based on a qualitative methodology with a comprehensive - descriptive perspective. A group of twenty-two students was analyzed at a generalized level in the mentioned categories and also, an insightful analysis of three learners with the purpose of determining changes in their cognitive representations. Paralleling the initial test with the final one, it was established that 31.8% of the pupils is placed on the physical - process category, 63.6% on the chemical - process category, and only 4.5% of them does not indicate the interaction; this evidences the progressive conceptual change and the gradual distancing of previous ideas.

Resumo em Inglês:

The recovery of waste materials with potential for synthetic transformations is a major field in science. However, just few experiments have been devoted to undergraduate students by exploring some consistent subjects in light of simple, natural resources. Nucleophilicity is a central subject in chemistry and there are significant synthetic models to exploit it in contrast to basicity. Here we present a laboratory experiment that utilizes hands-on research to be implemented in an organic chemistry lab by using benzyl isothiocyanate (BITC) from papaya seeds as raw material for the preparation of thioureas in a fast and visually indicative experiment. Subjects such as green chemistry, extraction methods, nucleophilicity, chromatography and NMR spectroscopy can be emphasized in order to implement a project-based approach. This experiment shows flexibility concerning the procedures and the use of biomass raw materials towards the reinforcement of a research-like experience and critical-thinking skills.

Resumo em Inglês:

This theoretical paper proposes some pedagogical practices that may be applicable by chemical lecturers who teach in Chemistry teacher education courses. Those practices are based on three theoretical ideas: i) Johnstone’s triplet about the three levels of chemical knowledge (macroscopic, microscopic and symbolic) which imposes challenges due to the significance of chemical language, leading us to discuss ii) the importance of the verbal language in chemistry teaching-learning processes, and iii) in the role of investigative experiments for exploring students’ ideas and promote abstract thought. Those practices focuses on the relation of the chemical triplet with investigative experiments for promoting meanings’ negotiations between lecturer and his students by means of pedagogical mediations and discursive interactions. In this sense, some research contributions about chemical education are related with central ideas of the historical-cultural approach proposed by Vigotski and collaborators aiming to highlight the importance of chemical lecturers in chemistry teacher education courses.

Resumo em Inglês:

This paper aims to present a review of the concept doping in scientific journals published in the period 2008 to 2018. The diversity of approaches that position doping as a socially acute question (SAQ) allow us to recognize the implications of this concept in educational contexts. The state of the art methodology seeks to reflexively recover production on the meaning that is attributed in the literature to the knowledge, practices and social, political and educational implications of a subject as complex as doping. Among the trends found, the Analytical Chemistry approach is highlighted, associated with the studies carried out in the laboratories on techniques and methods for the detection of prohibited substances; the consequences in terms of costs and benefits of doping from biochemical and physiological studies; the set of ideas, conceptions and representations that people have against doping; the educational programs and the pedagogical proposals that study the psychological, epistemological and methodological foundations for the prevention of doping; and the legal aspects, public policies and debates around doping and competition rules.

Resumo em Inglês:

The development of fingermarks is an important step in criminal cases. Latent fingermarks require applications of reagents to be developed before they can be visualized. Different techniques to enhance fingermarks’ visualization have been employed and the powder dusting is the most common among them. The use of food spices as latent fingermarks developers could be an alternative method of experiment in chemistry teaching, considering that they are low cost and accessible. In this work, an experimental methodology was developed and can be applied in undergraduate chemistry teaching for the extraction of components from food spices, their chromatographic analysis and application on the development of latent fingermarks.

Resumo em Inglês:

A procedure for the assessment and optimization of the greenness of solvents in synthesis was developed. It involves two optimization components, aiming at the optimization of both the intrinsic greenness of the solvents and their efficiency to improve the overall green performance of the synthesis, evaluated with mass, energy and time greenness metrics. The procedure was tested in a study with educational purpose for assessing and improving the greenness of solvents used in the workup step of a ionic liquid synthesis that involves a solventless reaction step (1-hexyl-3-methylimidazolium chloride) and proved useful to systematize the aspects that should be considered to choose the solvents used in the workup. The results show that there may be a competition in the solvent choice between a safer solvent and a more hazardous solvent with better performance of the overall synthesis process, which requires optimization for reaching a balanced solution. The study illustrates the problems of the substitution of solvents in synthetic processes to improve greenness, as well as the importance of the utilization of a battery of greenness metrics for evaluation of the overall synthesis outcomes.

Resumo em Inglês:

The qualified preparation of technician chemistry students who will act directly in the operation and control of industrial chemical plants is a permanent challenge in the teaching-learning process, since such activities require a broad view of the process and a sum of knowledge’s areas such as unit operations, instrumentation and industrial process control. An alternative to better understand these chemical engineering subjects within the technician chemistry course is the use of didactic experiments, which aims to provide an approximation of the taught content in the classroom with practical operation in a dynamic way, facilitating the teaching-learning process. In this sense, this work aimed to propose to the students of the technician chemistry course integrated to high school to use their creativity, combined with the technical concepts studied in the classroom, to build didactic experiments of unit operations within the following topics: heat exchanger, adsorption, humidification and drying. The results were evaluated in the form of performance technical data and qualitative questionnaire. Results have evidenced the positive character in the teaching-learning process of the operating principles of the unit operations, besides allowing the students a direct contact with process control and industrial instrumentation.