Bruna Marine Damm

Green chemistry provides a framework for redesigning laboratory practices to reduce environmental and safety impacts. In elemental analysis, replacing highly concentrated acids during sample preparation represents an important step toward more-sustainable practices. This study evaluates three didactic case studies based on the use of diluted nitric acid for sediment preparation in analytical and environmental chemistry courses. The participants included secondary technical students in biotechnology (n = 5) and undergraduate chemistry students (n = 43) from the analytical and environmental chemistry course, who were encouraged to critically evaluate conventional procedures that employ concentrated acids. Before classroom implementation, the alternative protocol based on diluted nitric acid was examined to ensure its analytical feasibility. Data were collected through questionnaires, responses completed by students in a structured monitoring form during the activities. The students proposed new alternatives and different approaches to solving problems related to chemical activities. The results demonstrated that this approach enabled students to integrate new knowledge in a critical, creative, and collaborative manner. Furthermore, the didactic strategy provided favorable conditions and essential experiences for training future chemical professionals who are aware of and reflective of their actions.

A experimentação contextualizada e problematizada pode fomentar a participação de estudantes do ensino superior em química, além de aprimorar suas habilidades para diversos temas científicos. Este trabalho teve como objetivo desenvolver e aplicar uma atividade experimental problematizada (AEP) baseada na determinação da composição inorgânica majoritária de amostras de mel de abelhas sem ferrão (ASF). Para isso, os estudantes realizaram dois experimentos: teste de chamas e espectrometria de fluorescência de raios X (XRF). A estratégia didática permitiu mobilizar conhecimentos de química inorgânica no contexto dos méis de ASF de forma colaborativa e experimental. Por meio dos indicadores de desenvolvimento de capacidades (IDC), verificou-se que os estudantes mobilizaram habilidades analíticas (RM: 5,8–6,1), práticas (RM: 5,2–6,0) e criativas (RM: 5,1–6,1), evidenciando progresso positivo durante a AEP. Os resultados indicam que a AEP contextualizada contribui para a formação inicial de licenciandos em química, promovendo aprendizagem significativa, desenvolvimento de competências experimentais e integração entre teoria e prática.

Chemical compounds found in stingless bee honey (SBH) may impact their biological properties; therefore, the establishment of quality control and standardization protocol is essential. This study investigated the chemical composition and antioxidant capacity of SBH produced by Melipona species from the Espírito Santo state (Brazil). A comprehensive characterization of SBH was conducted using Fourier transform mid-infrared (FT-MIR) and nuclear magnetic resonance (NMR) spectroscopy combined with chemometrics tools. A principal component analysis (PCA) model based on FT-MIR signals showed the separation betweenMelipona capixaba and Melipona quadrifasciata. Volatile organic compounds (VOCs) were detected by gas chromatography–mass spectrometry (GC–MS), and the more abundant classes of the classes were carboxylic acids, ketones, aldehydes, and alcohols. Moreover, the PCA model based on partial GC–MS chromatograms allows the grouping into M. capixaba and M. quadrifasciata. Simple phenols such as p-cresol and allyl guaiacol were also identified in SBH. In addition, total phenolic contents (TPC) and total flavonoid contents (TFC) had selective correlations with total antioxidant capacity (TAC). A high Pearson correlation was observed between TPC and ceric reducing antioxidant capacity (CRAC), although there were low correlations among TAC values. Chemometrics combined with phenolics and antioxidant capacity are comprehensive approaches to determine the identity and quality of SBH.

Quality parameters, physical-chemical characteristics, and antioxidant capacity are important to ensure the successful commercialization of honey. On the other hand, the presence of antioxidants in foods gives them greater added value. Thus, based on the study of total antioxidant capacity (TAC), along with the analysis of total phenolic compounds (TPC) and total flavonoid compounds (TFC), it is possible to classify honey according to its composition. First, all the samples were evaluated according to their polinic origin (melissopalynological analysis). The TAC was determined using both spectrophotometric methods (ferric reducing antioxidant power, FRAP) and electrochemical methods (ceric reducing antioxidant capacity, CRAC). All types of honey exhibited significant values for TAC, TPC, and TFC. To assess honey quality, methodologies such as moisture content, diastase activity, hydroxymethylfurfural (HMF), total acidity (TA), and water activity (A _w) were employed. Among the analyzed samples, 5 and 2 honey showed high levels of moisture (20.10-20.87%), TA (65.12-65.49 mequiv kg^-1), and HMF (>60 mg kg^-1), surpassing the limits set by Brazilian legislation. This indicates a potentially longer shelf life or the possibility of adulteration. Furthermore, it was concluded that the color of honey may interfere with FRAP (r = 0.837). In this regard, the CRAC assay presents a new alternative for evaluating TAC in bee products.

EXTRACTION OF BENZYL ISOTHIOCYANATE (BITC) IN CHEMISTRY TEACHING THROUGH THE PROBLEMATIZED EXPERIMENTAL ACTIVITY (PEA): POSSIBILITY OF REUSING PAPAYA SEEDS. This study investigated the reuse of papaya seeds for the extraction of benzyl isothiocyanate (BITC) as a context to foster the construction and deepening of chemical concepts in the initial training of chemistry teachers at the Federal University of Espírito Santo (UFES). Using Problematized Experimental Activity (PEA) as a teaching strategy, students conducted experiments to extract BITC from papaya seeds and applied ultra-violet (UV)-visible spectroscopy for its quantification. The results revealed that the highest BITC concentration was obtained from ethanolic extracts of dried seeds. At the end of the course, students developed teaching projects to incorporate this environmental theme into high school classes, reinforcing the relevance of contextualized chemistry teaching. The didactic intervention carried out in an environmental context contributed significantly to the training of future teachers, fostering meaningful learning and promoting a critical and conscious stance on the role of Chemistry in environmental issues.

Resumo A prática da metacognição na condução das atividades de ensino potencializa o processo de aprendizagem do estudante e melhora seu desempenho acadêmico. Tendo em vista a demanda e a importância do acompanhamento da aprendizagem que mensurem as capacidades desenvolvidas pelos estudantes, se propõe a elaboração e análise de indicadores metacognitivos das aprendizagens, a partir da aplicação da metodologia de ensino denominada aprendizagem baseada na resolução de problemas (ABRP) nas aulas de química analítica. Para isso, elaborou-se previamente indicadores que foram destinados à avaliação de três capacidades metacognitivas: a criativa, a analítica e a prática. Estes indicadores foram estabelecidos em conformidade com a teoria triárquica da inteligência, de Robert Sternberg. Esse levantamento possibilitou as reflexões e decisões sobre os pressupostos do autoconhecimento dos estudantes em termos de suas características e capacidades, e por outro lado, atentou-se na análise das especificidades das tarefas acadêmicas realizadas durante a execução da ABRP.