Química Nova, Volume: 45, Issue: 3, Published: 2022
  • ENANTIOSELECTIVE SEPARATION OF OXYBUTYNIN: A THEORETICAL AND EXPERIMENTAL INVESTIGATION Artigos

    Zin, Lilian Christina; Silva, Camilla Fonseca; Guimarães, Luciana; Borges, Keyller Bastos; Nascimento Jr., Clebio Soares

    Abstract in Portuguese:

    In this work, we have studied both experimentally and theoretically the oxybutynin chiral discrimination. According to the main results, the enantioseparation of oxybutynin was efficiently achieved by high performance liquid chromatography in normal phase using the Chiralpak® AD column, which has amylose tris (3,5‐dimethylphenylcarbamate) as a chiral selector. The energetic and structural parameters obtained via density functional theory calculations pointed out the chiral discrimination as well as the enantiomeric elution order of oxybutynin, thus explaining, at molecular level, the experimental data. Finally, the strength of the hydrogen bonds played a key role in the discrimination between the oxybutynin diastereomeric complexes formed.
  • MOLECULAR NETWORKING-BASED DEREPLICATION OF AMBUIC ACID DERIVATIVES FROM THE MARINE FUNGUS PESTALOTIOPSIS SP. 4A11 Articles

    Kellner Filho, Luis C.; Assis, Rhenner N. A.; Santos, Aline O. dos; Targanski, Sabrina K.; Siqueira, Kátia A.; Medeiros, Livia S. de; Angolini, Célio F. F.; Silva, Felipe M. A. da; Soares, Marcos A.; Dias, Gustavo M.; Silva, Marcio L. A.; Cunha, Wilson R.; Pauletti, Patricia M.; Koolen, Hector H. F.; Januario, Ana H.

    Abstract in English:

    Ambuic acid (AA) is a highly-modified cyclohexenone and known as a promising inhibitor of quorum sensing in methicillin-resistant Staphylococcus aureus, and is thus a candidate as an antivirulence drug. This molecule is mainly produced by the species of Pestalotiopsis and, since its discovery twenty years ago, only a restricted amount of AA-derivatives have been described. Despite being a promising subject, methods for the analysis of modified AA-analogues via mass spectrometry remain unexplored. In order to adress this question, the marine fungus Pestalotiopsis sp. 4A11 associated with the ascidian Didemnum perlucidum was grown in a solid rice medium and its crude extract was chemically studied. From this extract, AA and 10-hydroxy ambuic acid (10-HAA) were isolated and identified using NMR spectroscopy with the aim of obtaining model compounds for the MS analysis. These served as reference compounds (seeds) to guide the dereplication of other AA-analogues via LC-MS/MS-based molecular networking. Based on the manual interpretation of the fragmentation pathways of the seeds and related compounds observed in the networks, six AA-derivatives were dereplicated in the extract. Furthermore, three analogues with unprecedented chemical formulas were proposed as putative unprecedented AA-derivatives. The fragmentation annotation proposed represents a fast and feasible method for characterizing AA-derivatives.
  • THEORETICAL INVESTIGATION OF THE EFFECT OF CONJUATION OF THIOPHENE RINGS ON THE CHARGE TRANSPORT OF THIENOCORONENE DERIVATIVES Articles

    Chen, Ziran; Zhang, Yujin; He, Zhanrong; Li, Yuan; Xia, Meihao; Yu, Wenhao

    Abstract in English:

    Based on density functional theory, quantum chemical calculations of the charge-transport rates were performed for five disc-shaped coronene derivatives with varying numbers of fused thiophene rings, using different basis sets 6-31+G(d) and 6-311++G(d,p), hybrid functionals (B3LYP, M06-2X, CAM-B3LYP, WB97XD, M08-HX), and a dispersion-corrected hybrid functional (M06-2X+D3). Our results indicate that increasing the basis set and adding diffusion and polarisation functions had little effect on the molecular reorganisation energy, charge-transport matrix element t, and charge carrier mobility μ. The charge carrier mobility calculated using B3LYP were relatively large, whereas the results calculated using CAM-B3LYP and WB97XD were similar. Among the five coronene derivatives, molecule b with one thiophene ring could be candidates for a n-type organic semiconductor, and molecule c with two thiophene rings can be designed as a p-type semiconductor.
  • BILIARY PAH METABOLITES IN FISH FROM THE HIGHLY IMPACTED GUANABARA BAY, IN SOUTHEASTERN BRAZIL, DETERMINED BY FIXED AND SYNCHRONOUS FLUORESCENCE SPECTROSCOPY Articles

    Freire, Marina Moreira; Gómez, Cristina; Oliveira, Anabela Sousa; Moreira, Josino Costa; Arias, Ana Rosa Linde

    Abstract in English:

    Guanabara Bay (GB) covers the metropolitan region of the state of Rio de Janeiro in Brazil. GB is subject to heavy contamination by polycyclic aromatic hydrocarbons (PAHs), from intense oil activities, which pose an ecotoxicological threat. The aim of this study is to implement and optimize a fluorescence methodology for the determination of biliary PAH metabolites in fish species (burrfish and whitemouth croaker), in order to evaluate biliary PAH metabolites as a biomarker of exposure. Fish were sampled from GB and a control region. Naphthalene, pyrene and benzo(a)pyrene metabolites were determined by Fixed Fluorescence Method (FF), while 1-hydroxypyrene was assessed by Synchronous Fluorescence Spectroscopy (SFS). The implementation and optimization of the FF and SFS methods allowed the determination and evaluation of the exposure of these species to PAHs of pyrogenic and petrogenic origin. Biliary PAH metabolite determinations was proven to be a useful tool for environmental monitoring contamination assessments.
  • FORMATION OF AZEOTROPES FROM THE STANDPOINT OF SOLVATION THERMODYNAMICS Artigos

    Pliego Jr., Josefredo R.

    Abstract in Portuguese:

    The formation of azeotropes is related to the deviation of the ideality of liquid mixtures. This deviation is expressed by the activity coefficient of each component. However, the physical origin of this behavior is not well quantified in terms of molecular interactions. In this work, a regular solution model was used, relating the β parameter to the solvation free energy of pure liquids in themselves and in the other component. A mathematical expression was derived that indicates when an azeotrope is formed. This equation shows that the greater the difference in vapour pressure between components, the greater the solvation difference of each liquid in itself and in the other component is needed to form the azeotrope. A set of 10 mixtures were randomly chosen and investigated as a test, and the equation worked in all cases.
  • EXEMPLIFYING THE USE OF MACRO ELEMENTAL MAPPING BY XRF (MA-XRF) SCANNING IN FORENSIC INVESTIGATION OF ARTWORKS Artigos

    Pimenta, André R.; Felix, Valter S.; Silva, Daniele M.; Pereira, Marcelo O.; Oliveira, Ana L.; Ferreira, Douglas S.; Carvalho, Cristiano S.; Silva, Fabricio L.; Gonçalves, Elicardo A.S.; Dutra, Rafael S.; Pereira, Leandro O.; Pereira, Ronaldo V.; Freitas, Renato P.

    Abstract in Portuguese:

    EXEMPLIFYING THE USE OF MACRO ELEMENTAL MAPPING BY XRF (MA-XRF) SCANNING IN FORENSIC INVESTIGATION OF ARTWORKS. This work exemplifies the potential of employing macro elemental mapping by XRF (MA XRF) scanning in the forensic investigation of artworks. The results of the investigation of two artworks of different styles and periods are presented and discussed. The images provided by MA-XRF scanning have information about the elemental distribution, which is related to pigments used in the artwork. These images bring different information such as: if there are underlying paintings; if a given pigment was used for the purpose of restoration or in the creation. Therefore, through the images, it is possible to obtain information, which refers to the process of creating the artwork and the history of conservation and restoration. Through the results, it was possible to verify that the two artworks are probably false because they present anachronistic pigments with the supposed period of creation. The analyzes were performed using a portable MA-XRF scanning system, and in addition to presenting the utility of the instrument in these investigations, the work also presents possibilities to explore the MA-XRF data through multivariate statistical analysis and image correlation.
  • ENZYMATIC, CHEMOENZYMATIC AND PHOTOENZYMATIC CASCADE REACTIONS: PERSPECTIVES FOR A MORE SUSTAINABLE ORGANIC SYNTHESIS Revisão

    Castilho, Shirley A.; Milagre, Humberto M. S.; Milagre, Cintia D. F.

    Abstract in Portuguese:

    Chemicals are rarely the result of a single transformation but rather the consequence of several individual reaction steps. Classically, these individual steps are carried out in sequence, including isolation and purification of the intermediate products. However, the reasons for choosing to carry out cascade reactions can be multiple, such as (i) the chance to prepare unstable and/or toxic intermediates, which are consumed directly in a subsequent step, (ii) the option to shift the equilibrium of a reaction by removing the co (product), or (iii) simply bypass the tedious work of isolating and purifying intermediates, saving reagents, solvents, time and money, and still generating less waste. Therefore, it is not surprising that so-called cascade reactions are gaining considerable interest in academic and industrial research. The purpose of this review is to show recent, promising research and new trends, the potential and current limitations of cascade reactions in organic synthesis that involves at least one enzymatic step in the cascade. This review will address cascades involving multi enzymatic, chemoenzymatic, and photoenzymatic cascades, where all steps are performed in one reaction vessel simultaneously or sequentially and the cascades in the regime of continuous flow.
  • ANALYTICAL ADVANCES BASED ON FIRST-ORDER CALIBRATION MODELS AND UV-VIS SPECTROSCOPY FOR THE ASSESSMENT OF WATER QUALITY: A REVIEW – PART 1 Revisão

    Santos, Grazielle R.; Paulino, Gabriela S. P.; Borges, Grazielle P. I.; Santiago, Aníbal F.; Silva, Gilmare A. da

    Abstract in Portuguese:

    This work aimed to infer about the scientific progress of the use of ultraviolet-visible (UV-Vis) spectrophotometry for evaluations of water quality. The research started in the 60s, when the imminence of obtaining characteristics of the UV-Vis spectrum that estimated the water quality. From a temporal perspective, the 1990s began using first order multivariate calibration models, focus of this work, to predict water quality parameters utilizing the UV-Vis spectra. During the period evaluated, numerous studies used spectrophotometry to quantify analytes using univariate calibration. However, many works also report the fact that the determined substances absorb at the same wavelengths and describe how to resolve these interferences. But gaps such as low concentration determinations are still a bottleneck as the best results, for example, are related to high amounts of organic matter, fact also related to instrumental aspects. One of the gains was the introduction of chemometric approaches which allows quantification without the need of analytical curve construction during the prediction step. However, although they are already used techniques, the survey carried out here verified the applications are considered incipient, where, for example, dissolved organic carbon and nitrate predictions using first order multivariate calibration represent less than 30% of the determinations.
  • ALCOHOL GEL FOR ASEPSY OF THE HANDS - PROPER FORMULATION AND GUARANTEED EFFICIENCY AMID THE PANDEMIC OF COVID-19 Nota Técnica

    Ferreira, Kleber Queiroz; Rigoli, Isabel C.; Silva, Marcus V. S. da; Espeleta, Alexandre de Freitas; Rocha, Zênis Novais da

    Abstract in Portuguese:

    The use of hand antiseptics became widespread as a routine in the fight against COVID-19. In the market, the availability and purchase of substandard antiseptics create a permanent concern with safety, even after a pandemic. Therefore, the development of easy-to-deploy analytical methods for the quality control of alcohol-based hand antiseptics is needed. In this work, to determine the ethanol content in alcohol gel the use of refractometry and alcohol oxidation method by dichromate accompanied by UV-Vis spectroscopy were applied. The results indicated that 19 brands (out of the 70 evaluated) (27.1%) had levels of ethyl alcohol below the recommended level (68.25%), therefore, they are ineffective for hand asepsis. For the quality control of hand antiseptics, refractometry and the oxidation-reduction reaction are complementary analytical methodologies. As a quick, inexpensive screening method, refractometry provides a more suitable technique. However, the interference of emollients may affect the accuracy of the ethanol content determination. Therefore, applying the ethanol oxidation method coupled with electronic spectroscopy offers a simple and broadly accessible method to confirm the ethanol content in alcohol-based hand antiseptics. In addition to developing quality control protocols, is also described the 3.5-ton production of alcohol gel at the Federal University of Bahia.
  • CHEMICALS AND THE ENVIRONMENT: HISTORICAL ASPECTS AND THE CONTRIBUTIONS OF ENVIRONMENTAL MANAGEMENT TEACHING Educação

    Alves, Suellen A.

    Abstract in Portuguese:

    Global environmental issues have gained strength since the 1960 decade and the relationship between the chemical industry and the environment has become increasingly tight since then. In this sense, environmental management has gained more space making organizations think strategically about their business and the possible impacts that they can promote on the environment. The present paper shows two brief timelines: the history of the chemical industry and the important events for environmental issues. In addition, it reports an investigation into the insertion of the discipline of environmental management in curricular matrices of institutions in Paraná and didactic experiments carried out at the State University of Ponta Grossa: simulation of environmental audit and analysis of the environmental management of the chemistry teaching laboratories of that institution a from the survey of environmental aspects and impacts and the elaboration of the environmental risk index. Finally, a questionnaire is shown with the graduates who took the discipline and how they perceive the importance of it in professional life. The reflection on social and environmental responsibility is extremely important for sustainable development and the chemist has a leading role in this path.
  • USING ANALOGIES TO TEACH ABOUT THE ATOM IN HIGHER EDUCATION GENERAL CHEMISTRY CLASSES Educação

    Arão, José; Leite, Laurinda; Nhalevilo, Emília

    Abstract in Portuguese:

    Chemistry deals with concepts associated with non-observable entities. Using analogies may facilitate the learning of such concepts, including the atom. In this study, we investigated the analogies that two chemistry teachers used when teaching about the atom at two Mozambican universities. These analogies were characterized and the reasons that led teachers to use analogies were analyzed. Teachers were observed when teaching about the atom and they were interviewed afterwards. Both teachers used different amounts of analogies, which focused on the Thomson and the Rutherford models. Almost all the analogies, that were created and used spontaneously, showed a lack of internal consistency, which may reduce their didactical value and even make them inducing incorrect ideas in the students. Teachers stated that they would start planning the use of analogies in their classes. If they are to do this properly, they need training that integrates two components: analogies and chemistry.
  • ANALYSIS OF ENVIRONMENTAL SAMPLES FOR NUCLEAR SAFEGUARDS PURPOSES IN BRAZIL Assuntos Gerais

    Lisbôa, Carina C.; Oliveira Júnior, Olívio P. de; Andrade, Delvonei A. de

    Abstract in Portuguese:

    The International Atomic Energy Agency (IAEA) is responsible for preventing the proliferation of nuclear weapons by detecting early the misuse of nuclear material or technology, and by certifying that States are honouring their safeguards obligations. The analysis of environmental samples taken by IAEA inspectors during inspections is a powerful tool for nuclear safeguards. This tool was implemented in 1996, after a successful application in Iraq, when a clandestine nuclear weapons program was discovered. The science involved in this type of analysis depends on highly sensitive and selective analytical measurements for detecting traces of nuclear materials collected in the nuclear facility’s “environment”. The purposes of this article are to draw attention to the relevance of this subject in order to address a significant global problem and to present what have been developed in Brazil. Through compatible results with certified standards and IAEA requirements, Brazil has already demonstrated the potential of measuring the amount and isotopic composition of uranium and plutonium at the levels expected in typical environmental samples. Finally, this work suggests the necessary measurements to implement a reliable and consistent environmental samples program for nuclear safeguards in Brazil.
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