Resumo em Inglês:

In this work, multivariate optimization techniques were applied to develop an acid digestion procedure in digester block using “cold finger” as reflux system to determine minerals in almond pulp samples by inductively coupled plasma optical emission spectrometry. Two-level full factorial design and Box-Behnken design were applied to evaluate and optimize the factors involved in the acid digestion process. In both experimental designs, Function D and Function MR multiple responses were used to establish the method condition for all analytes and with greater digestion efficiency. Two apple and spinach leaves certified reference materials were analyzed to confirm the proposed method accuracy. The digestion efficiency was evaluated by residual carbon content which showed 1.32-1.77% range. The concentration values found for each element in almond pulp collected in Salvador, Bahia, Brazil in mg 100 g-1; were: 3.08 (Ca), 0.209 (Cu), 0.407 (Fe), 356 (K), 21.5 (Mg), 0.096 (Mn), 34.4 (P) and 0.289 (Zn). The developed method was simple and efficient for almond pulp mineral composition evaluation. This unconventional fruit has nutritional relevance with future application for new food recipes and pharmaceutical products formulation.

Resumo em Inglês:

The liquid-liquid extraction with low-temperature partitioning technique (LLE/LTP) was miniaturized to determine the pesticides chlorpyrifos, bifenthrin, λ-cyhalothrin, and deltamethrin in a biological matrix, by gas chromatography. The method was proposed for fetal-bovine serum samples (500 μL), by using a full factorial design (23) with one center point. The evaluated factors included the volume of water added to the sample (1000 μL), volume of extraction solvent (500 μL) and stirring time (60 s) – a cleanup step was not necessary. The method was validated for the main figures of merit. The results indicated that the LLE/LTP/GC/ECD miniaturized method was efficient in extracting pesticides from blood-serum samples (75 to 115%). It showed both selectivity and sensitiveness, with limits of quantification (LOQ) ranging from 8 at 17 μg L-1;. Once validated, the method was applied to blood-serum samples of rural workers from a city in the Brazilian state of Minas Gerais. In that case, the presence of chlorpyrifos was detected in two of the samples.

Resumo em Português:

PREPARATION OF IRON/CARBON MATERIAL FROM BIODIESEL WASTE FOR APPLICATION IN THE REMOVAL OF ORGANIC CONTAMINANTS. In this work, iron/carbon-based catalysts obtained from biodiesel residues, glycerin, were prepared. The composites were prepared by thermal carbonization of the glycerin polymer, from biodiesel residues, in the presence of iron salt. The materials obtained were characterized by adsorption/desorption of N2, scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and thermogravimetric analysis. XRD analysis have shown the presence of hematite and magnetite. The methylene blue (MB) adsorption and oxidation tests reached 99% color removal in the presence of hydrogen peroxide. The steadystate spectra confirmed the MB oxidation by the reduction of the fluorescence intensity. Besides, it has high stability, with no active phase leaching, proving a heterogeneous oxidation process.

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ANALYTICAL METHOD FOR DETERMINATION OF AURAMINE DYES IN ECOTOXICITY TESTS AND IN SURFACE WATERS. Dyes can be considered important environmental contaminants. Auramine dyes, known commercially as Solvent Yellow 34 and Basic Yellow 2, are used in several industrial products, including textile and paper. In this study, an analytical method was developed and validated using Liquid-Liquid Extraction and High-Performance Liquid Chromatography coupled to Diode Array Detector (LLE and HPLC-DAD) to determine the exposure concentrations in the ecotoxicological tests with auramine dyes, increasing the results reliability about the hazard of these compounds. The method was also used to monitor auramine dyes in surface water samples, in a region considered one of the most critical regions for dyes contamination in Brazil. The results showed no risk for the aquatic organisms considering the analyzed samples. The method using simple instrumentation showed the results of selectivity, linearity (R2> 0.99), precision (CV: 5.6-29%) and accuracy (recovery: 82-90%) considered satisfactory for the two purposes with Instrumental LOQ of the 12 µg L-1; and the Method LOQ of the 12 ng L-1;. The results indicated that the proposed method was effective and practical for the auramine determination in environmental levels and will be an important tool to verify the potential risk of auramine dyes in future studies.

Resumo em Inglês:

The controlled release of Salicylic Acid (SA) influences the concentration and collateral effects of the drug. This release refers to the matrix in which the SA is incorporated. Among the matrices, Fe3O4 nanoparticles (NPs) stand out, for transporting drugs to specific sites. The functionalization of Fe3O4 by bovine serum albumin (BSA) can improve colloidal and chemical stability, in addition to increasing interactions with drugs. Thus, understanding the release kinetics of the AS incorporated in Fe3O4-BSA is essential to improve the controlled release. The study aimed the synthesis, characterization and release of the SA into the Fe3O4-BSA NPs. The results showed the functionalization of the Fe3O4-BSA NPs was effective and the average size was below 30 nm. The NPs showed colloidal stability above the pH of 7.5 which can be used as a drug carrier in blood plasma. Drug encapsulation into the NPs system was efficient (~91%) with about 30% of drug loading capability. The kinetic results showed the SA release mechanism was controlled by diffusion. The conclusion is that the incorporation of SA in Fe3O4-BSA NPs led to a release of SA in the first six hours, reaching equilibrium at 0.265 mg mL-1; and 1.83 mg.

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THE STATE OF THE ART OF VOLATILE CARBONYL COMPOUNDS IN INTERNAL ENVIRONMENTS: IMPACTS TO HEALTH AND SAMPLING METHODOLOGIES AND ANALYSIS. The primary sources of emission of volatile carbonyl compounds (CCs) in indoor environments are chipboard panels, laminate floors, plywood, paints and solvents, household products, fiberglass, gas stoves, heaters and heating systems. Several studies have already confirmed an indoor/outdoor (I/O) ratio greater than 1 (one) for several CCs, indicating that these compounds are emitted mainly from internal sources. CCs (especially aldehydes and ketones) are easily absorbed into the airways, presenting a considerable mutagenic, teratogenic and carcinogenic risk to humans. Therefore, this study aimed to review the CCs found in different indoor environments, the effects and impacts of these compounds on human health and the national and international guidelines that establish their maximum exposure limits. The methodologies most used in the literature to analyze CCs in the air were reviewed directly (in real-time) or indirectly (using pre-treatment steps). A detailed review of the sampling techniques: with and without adsorption, with and without derivatization, with adsorption and derivatization simultaneously; using various methodologies employed during the last decades (cartridges, filters, tubes or liquid absorbent-impinger) was carried out. Finally, this work describes the instrumental methods and the advantages and disadvantages of determining CCs individually and simultaneously in the atmosphere.

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ORGANOMETALLIC COMPOUNDS OF TIN(II) - SOME MAIN GROUP METAL STANNYLS. This paper aims to summarise some chemical information about selected main group metal stannyl compounds. The number of these compounds in the literature are much fewer than those with transition metal cations. Most papers report details of stannyls containing Li(I), Na(I) and K(I), such as synthetic routes, spectroscopic results and their molecular structures. This review comprises not only information of stannyls containing these cations, but also some alkaline-earth species containing Mg(II), Ca(II), Sr(II), Ba(II), as well as Sn(II). In some compounds, the alkaline or alkaline earth cation is connected to the stannyl fragment through a Sn – M bond, evidenced by X-ray crystallographic data or by solution- or solid-state 119Sn NMR experiments. The introduction part of the paper summarizes the chemical aspects of these compounds and their importance in the organometallic chemistry of Sn(II) as a research area. The second part of this review is dedicated to a broad discussion of the syntheses and structural aspects of some Li(I), Na(I) and K(I) derivatives. The structure of some stannyl compounds of Mg(II), Ca(II), Sr(II), Ba(II) are displayed in the third part of this paper. Two rare examples of Sn(II)-based stannyl derivatives are shown in the final part of the review. This review also highlights how important it is to correlate X-ray crystallographic data with those obtained by solution- or solid-state 119Sn-NMR experiments in order to determine the degree of covalence in the Sn – M bond.

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STRATEGIES FOR THE SYNTHESIS OF LYSERGIC ACID. (+)-Lysergic acid [(+)-1] is a precursor of several substances with well-established pharmacological properties, including some drugs approved and commercialized around the world. Thus, the importance of (+)-1 as a synthetic target becomes undoubted and various strategies for the synthesis of its tetracyclic core have been reported in the literature. Therefore, in this review article we will address in chronological order the total and formal syntheses of lysergic acid (1), separating them into racemic and chiral/asymmetric syntheses. Until now, there are 24 syntheses described in the literature, namely, 11 total and 13 formal syntheses. Considering all the syntheses accomplished, 15 were planned to produce (±)-lysergic acid [(±)-1] and 9 presented routes to eventually provide (+)-lysergic acid [(+)-1]. A significant evolution regarding approaches and efficiency may be observed since the first synthesis of (±)-1 until the last asymmetric synthesis of (+)-1.

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DETECTION AND QUANTIFICATION OF SILVER NANOPARTICLES BY spICP-MS. The growing interest in nanotechnology has led to an increase in the production and application of nanoparticles worldwide. Due to the unique functional properties of nanoparticles, these materials are being used by many industries, including the agricultural and food sectors. Among the commercially available nanomaterials, it is possible to highlight those produced with silver nanoparticles. One of the most promising techniques for the analysis of metallic nanoparticles is the Inductively coupled plasma mass spectrometry (ICP-MS) performed in single particle mode (spICP-MS). However, the use of the technique in the detection and measurement of nanoparticles requires that the equipment be operated differently than when used to analyze dissolved metal solutions. Thus, this article presents the use of the spICP-MS technique for the measurement and quantification of nanoparticles, as well as their validation. The method proved to be adequate for the purpose, presenting a satisfactory result for the selectivity test and recovery of 83.7 (40 nm) and 77.6% (80 nm). The detection limits, determined for the most frequent size, dissolved silver concentration and particle concentration, were 17.5 nm, 0.736 ng mL-1;, 146 particles mL-1;, respectively. Thus, the results obtained indicated the possibility of using the technique to determine the size and concentration of silver nanoparticles.

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MIXTURE DESIGN AND OPTIMUM REGION VISUALIZATION WITH SPREADSHEETS AT EXCEL: A TUTORIAL. This tutorial shows how to perform the data treatment for mixture design with two and multiple responses. Two data sets from the literature were used to exemplify the calculations. A template in Excel was proposed to prepare contour plot and response surface to visualize the optimum region of the mixture, which usually is made with commercial computational programs. The desirability function was used in example 2 (optimization of 5 responses simultaneously), and a code also available for download was proposed. Besides, 21 videos were prepared to show all the details for the readers and, it is available on YouTube. With this tutorial, it is possible to learn in a practical fashion how to handle the data from mixture design and, the authors hope to contribute with the researchers in this area.

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A PROPOSAL FOR ANALYZING CHEMISTRY ISSUES AT ENADE ACCORDING TO THE COGNITIVE LEVEL OF DIFFICULTY. This article aims to present an analysis of the ENADE-Chemistry exam using a taxonomy based on the cognitive operations mobilized to solve the chemistry issues here called as Cognitive Level of Difficulty. In addition to identifying contents in the area of knowledge, skills and competences. All questions from the exams of the years 2011, 2014 and 2017 were analyzed; selected the statistical data present on the reports issued by INEP for four higher-educational institutions (UFRN, UTFPR, UFU and UFAM) and the percentages of the distractors indicated. These data were organized in an excel spreadsheet (database) that helped the comparisons of different variables. As a result, we observed discrepancies when comparing the variables of the ease index and the cognitive level of difficulty for the questions that addressed general chemistry concepts. For example, issues considered very difficult in the easiness rating, but which required low order thinking skills and reciprocally. We consider the proposed taxonomy of analysis of cognitive operations and the database is a tool that can contribute to their courses structure. Furthermore, the proposal can be extended to other areas.

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THE APPLICATION OF A COMIC STRIP, TRINITY, IN CHEMISTRY EDUCATION. Faced with obstacles encountered in lessons and the search for actions that meet current educational needs, some attention has been paid to the role of comics as instructional tool. This article focuses on the use of a comic strip, Trinity: A Graphic History of the First Atomic Bomb, to develop knowledge and promote science learning. Three case studies were extracted from the comic and implemented to a group of pre-service chemistry teachers. A questionnaire was utilized to assess their perceptions about the usefulness of comics for their learning. One hundred percent of students indicated that comics helped improve their understanding of the nature of science. On the basis of the data, comic strips may be utilized as an acceptable educational tool in science education.

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ESSENTIAL AND VEGETABLE OILS: RAW MATERIALS FOR THE MANUFACTURE OF BIOPRODUCTS IN CLASSES IN EXPERIMENTAL ORGANIC CHEMISTRY. A schedule was prepared for three undergraduate classes for the discipline of experimental organic chemistry for obtaining bioproducts. As natural raw materials, lavender flowers and cinnamon peels were used to obtain hydrolates and essential oils (Class 1), coconut and avocado pulp to obtain vegetable oils and annatto seeds to obtain a natural dye (Class 2). Cosmetic bioproducts (Class 3), body emulsions similar to those found on the market, were obtained from the mixture of essential and vegetable oils and the addition of natural dye. The raw materials obtained can also be used in other classes of the discipline, complying with the principles of Green Chemistry. Essential oils, for example, can be used as samples for Thin Layer Chromatography (TLC) classes and vegetable oils for the production of biodiesel.

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TEAM THAT GIVES ITS BEST. Football is the most practiced sport in the world, and admittedly one of the biggest cultural manifestations in Brazil. Its size and importance impact many fields of science. In this work, a playful and interactive activity is proposed, which allows the so beloved national sport and Chemistry to be united in a fun and reflective way, through the selection of the dream team. Each team can be formed by the desired tactical lineup, placing the player of your choice in the eleven available positions, describing its characteristic that makes it there. Even though it is derived from a competitive sport, there is no singular winner in this strategy, since everyone involved wins, due to the reflections and considerations developed, to the stimulus of creativity and to the fun involved in recreational activities like this.

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THE TELESCOPIC APPROACH AS A TOOL FOR GREEN CHEMISTRY. One-pot reactions have become a powerful tool for the development of sustainable protocols in organic synthesis. In particular, the telescoping of multi-step reactions, i.e., the execution of sequential reactions without isolating and purifying intermediates, reduces the number of steps while preventing waste generation. Additionally, the processes become more sustainable through time, reagents/solvents, energy and cost savings. Therefore, the aim of this work is to summarize and discuss representative one-pot telescoped strategies involving heterocyclic construction, cross-coupling and continuous-flow reactions.