Programa de Pós-graduação em Química

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As Licenciaturas em Química EaD nos IF e a Heutagogia como elemento basilar nos modelos de formação docente
(Universidade Federal de Goiás, 2024-08-27) Alves, Dylan Ávila; Mesquita , Nyuara Araújo da Silva; http://lattes.cnpq.br/6971106875143413; Mesquita , Nyuara Araújo da Silva; Cassiano, Karla Ferreira Dias; Lima, Daniela Da Costa Britto Pereira; Soares, Marlon Herbert Flora Barbosa; Silva Filho, Juvenal Carolino Da
This research aims to investigate the educational methodologies present in distance Chemistry Licentiate courses (LQ). It utilizes the theoretical perspectives of adult education in distance courses (Heutagogy) proposed by Stewart Hase and Chris Kenyon. The goal is to contribute to the discussion of the methodologies used in distance Chemistry courses at Federal Institutes (IF) that facilitate the learning process in these courses. The doctoral thesis was structured from chapters in the format of articles. For the conclusion of the thesis, three chapters/articles were developed titled: 1- Tensions in the Landscape of Chemistry Licentiate Programs in Brazil: Distance Education in Public and Private Spheres; 2- Heutagogy as a Methodology for Teacher Training at a Distance: An Overview of Brazilian Research; 3- An Analysis of Distance Chemistry Licentiate Programs in Federal Institutes from the Perspective of Heutagogical Learning Design Elements. Chapter 1 presents results from the survey of distance Chemistry Licentiate programs (LQ) in public and private higher education institutions (IES) in 2021, conducted through the e-MEC portal. A descriptive study with a quantitative-qualitative approach was used. The distance LQ programs represent a total of 20 courses in public institutions and 25 in private ones. The study highlights a trend towards teacher training through distance education, especially in private IES, but it also indicates the need for public institutions to investigate distance education training. Chapter 2 presents a survey of the main publications related to the Heutagogy theme in the Database of Theses and Dissertations (BDTD) from CAPES and in Portuguese journals. The research is configured as the "state of the art," divided into two moments: the first addresses the inventory of publications from 2010 to 2022, and the second identifies the trends in the publications regarding the theme. A total of 14 publications were surveyed, including five in the BDTD and nine in scientific articles. Initially, an analysis category was established as "Teacher Training," but two categories emerged: Distance Education and Heutagogy as a methodology. The study shows that there is no clear direction in research towards teacher training courses, but it presents Heutagogy as a potential theoretical reference in distance Licentiate courses. Chapter 3 analyzes the curricular proposals (PPC) of distance LQ courses in IF, based on the six learning elements proposed by Blaschke and Hase (2016). It was possible to reveal that the LQ programs present some learning elements in the documents, which can be evidenced in disciplines, evaluation criteria, supervised internships, curricular components, tutorial activities, among others.
Estudo da inserção de grafeno em catalisadores de PtSn para a oxidação de etanol
(Universidade Federal de Goiás, 2022-02-21) Bastos, Tarso Leandro; Colmati Junior, Flavio; http://lattes.cnpq.br/0231242349462585; Colmati Junior, Flávio; Ciapina, Eduardo Gonçalves; Martins, Paulo Roberto
Fuel cells are portable electrochemical converters that generate electricity using renewable fuels and can act as high-efficiency energy sources. When fed with ethanol, they lose performance due to electrode poisoning. To mitigate this problem, noble metals are used in the electrodes in addition to the addition of elements to the electrocatalysts, increasing the production cost while the problem persists. Thus, this study seeks to increase the efficiency of ethanol oxidation by modifying the carbon support with graphene, where the metallic phase is anchored, and to verify its influence on the general catalysis process. Electrocatalysts with carbon-graphene hybrid support were synthesized in different proportions, and a physical mixture of graphene with the carbon-supported electrocatalyst was prepared. Hybrid supported electrocatalysts showed higher electrochemical activity and stability in ethanol oxidation compared to carbon supported electrocatalyst, with an increase of 132% in alkaline medium. In the physical mixture, the addition of graphene generated a 10% decrease in the amount of metallic phase needed, obtaining the same performance as the pure electrocatalyst. While in acidic medium, in addition to the 10% decrease, the physical mixture exhibited a much superior performance to the pure electrocatalyst. The results showed that the influence of graphene depends on its interaction with the electrocatalyst, while promoting an increase in the performance of ethanol oxidation.
Abordagens para análise de n-nitrosaminas em medicamentos utilizando DPX-LC-MS e DART-MS
(Universidade Federal de Goiás, 2023-12-19) Batista Junior, Almir Custodio; Chaves, Andréa Rodrigues; http://lattes.cnpq.br/6064014965252121; Chaves, Andréa Rodrigues; Coltro, Wendell Karlos Tomazelli; Freitas, Carla Santos de
N-Nitrosamines (NAs) are molecules characterized by a deprotonated amine group linked to a nitroso group, usually formed through the reaction of secondary or tertiary amines with nitrosating agents. NAs are commonly found as impurities in various products, such as processed foods and cosmetics. These molecules are the subject of study due to their potential mutagenic and carcinogenic properties. In 2018, NAs were discovered in medicines containing the active ingredient valsartan. In sartan medicines, the occurrence of NAs was initially linked to the synthesis of the active pharmaceutical ingredient (API), as the reaction medium may contain precursor amines for NAs, as well as a nitrosating agent. Through more in-depth studies, it has been confirmed that the degradation of the API or its interaction with the packaging material could lead to the formation of NAs. These discoveries prompted global regulatory agencies to establish guiding principles regarding the presence and maximum allowable concentrations of these molecules in such medicines. Aiming to assess the content of NAs in medicines, efficient and sensitive analytical methods have been developed. The challenge in analyzing NAs in medicines lies in the low concentration of these analytes, as they are found in this matrix in the order of ng of N-nitrosamine per mg of the medicines. The literature presents various chromatographic methods coupled with mass spectrometry (MS) applied in such analyses. Both liquid chromatography (LC) and gas chromatography (GC) techniques provide sensitive and selective methods for the analysis of NAs in medicines. However, LC methods have advantages over GC as it allows the analysis of thermally unstable and non-volatile compounds. Due to the presence of the API in the sample and the low concentration of these impurities, the determination of NAs can be compromised by various factors, such as matrix effects, carryover effects, and the compromise and contamination of the LC-MS system. Thus, the sample preparation step proves to be important, aiming at the extraction, purification, and pre-concentration of NAs. Additionally, advances in mass spectrometry have led to the development of ambient ionization techniques designed to analyze samples that are either unprocessed or minimally modified in their native environment. These techniques enable the analysis of samples in situ, often in a non-destructive manner. Another important factor currently is the adaptation of analysis protocols with sustainable principles advocated by green chemistry, which aim to reduce the use of solvents and samples, minimize risks, decrease energy consumption, and reduce waste generation. Therefore, the present study introduces new approaches to the analysis of NAs in medicines that have not yet been explored in the literature. Chapter I demonstrates the use of a miniaturized sample preparation technique for the separation and pre-concentration of NAs in medicines followed by LC-MS analysis. Conversely, Chapter II presents the application of an ambient ionization technique coupled with mass spectrometry for the assessment and quantification of NAs in medicines.
Estudo de degradação forçada e de compatibilidade do ciprofibrato com excipientes farmacêuticos
(Universidade Federal de Goiás, 2022-08-31) Brito, Camila Cíntia Sousa Melo; Leles, Maria Inês Gonçalves; http://lattes.cnpq.br/1614912440064013; Leles, Maria Inês Gonçalves; Siqueira, Adriano Buzutti de; Chaves, Andrea Rodrigues; Ionashiro, Elias Yuki; Ribeiro, Elton Brito
Ciprofibrate-CPF is a hypolipidemic that promotes the reduction of serum levels of cholesterol and triglycerides by stimulating activated nuclear receptors for peroxisome proliferation-alpha-PPAR-α. In this work, the stability of CPF was studied using forced degradation and compatibility studies. The Active Pharmaceutical Ingredient-API (SQC) was characterized by Thermogravimetric Analysis/Derivative Thermogravimetric AnalysisTGA/DTGA, Differrential Scanning Calorimetry-DSC, Differrential Scanning Calorimetry coupled to the Photovisual system-DSC-Photovisual, Absorption spectroscopy in the mid-infrared region with Fourier Transform-FTIR, Nuclear Magnetic Resonance-RMN, Powder X-ray Diffractometry-DRXP, High Resolution Mass Spectrometry-EMAR and High Performance Liquid Chromatography coupled with Diode Array Detector and High Resolution Mass Spectrometry-CLAE/DAD/EMAR. The forced degradation study was carried out for CPF (SQC) under the following conditions: acid hydrolysis, basic hydrolysis, oxidative and thermal at 70 °C 240 hours using EMAR and CLAE/DAD/EMAR. The compatibility study between the CPF and the excipients was carried out by preparing binary mixtures in the proportions 50:50 and 92:08 (m/m), where the isolated components (CPF (SQT) and excipients), Simulated Excipients Sample-ASE (excipients) and the binary mixtures (CPF-excipient or CPF-excipients) were analyzed by TGA/DTGA, DSC, DSC-Photovisual, FTIR, and DRXP. The EMAR and CLAE/DAD/EMAR results suggested the degradation of CPF when subjected to basic hydrolysis, with some degradation products previously reported in the literature being observed and a new product identified. In the other exposure conditions, the CPF remained stable. The DSC technique suggested signs of interaction between the CPF and the excipients (Sodium Starch Glycolate-AGS, Sodium Lauryl Sulfate-LSS, Silicon Dioxide-DOS and Hydrogenated Vegetable OilOVH) when prepared in a proportion 50:50 (m/m) and between CPF and the excipient (OVH) in a proportion (92:08 m /m). However, the FTIR and DRXP techniques did not confirm the sings of interaction observed in the DSC, except when DOS was used at 50%. The compatibility study indicated the use of the CPF-ASE binary mixture in the proportion 50:50 (m/m) as a candidate for pre-formulation.
Implantação das técnicas espectroscópicas de Laser FlashFotólise e de fosforescência para estudos fotofísicos de sistemas porfirínicos e suas interações com biomoléculas e nanoestruturas
(Universidade Federal de Goiás, 2023-12-14) Ducas, Eli Silveira Alves; Gonçalves, Pablo José; http://lattes.cnpq.br/0515343409614452; Gonçalves, Pablo José; Coelho , Felipe Lange; Gomes, Danielle Cangussu de Castro; Lopes, Jefferson Marcio Sanches; Patrocínio, Antônio Otávio de Toledo
The photophysical characterization allows the assessment of processes following the phenomenon of light absorption, which is of interest for various applications, both in the field of materials chemistry and in photomedicine. This work aimed at the photophysical characterization of potential porphyrinic photosensitizers and their interaction with biomolecular systems and nanostructures. To achieve this, the spectroscopic techniques of Transient Absorption (or Laser Flash-Photolysis) and a Spectrophosphorimeter were implemented, and their usage protocols were established. With these techniques in operation, an alternative method for determining the triplet state formation yield and obtaining the singlet oxygen formation yield was proposed, fundamental properties for the characterization of photosensitizers. It was possible to investigate the interaction of water-soluble porphyrins with bovine serum albumin and verify that this interaction affects the triplet states lifetimes and singlet oxygen yields. These parameters were strongly influenced by the presence of oxygen and the porphyrin's location at the interaction sites in the protein structure. Another study conducted was the interaction of cationic porphyrins with manganese ferrite (FeMn2O4) anionic ferrofluids in which the interaction leads to the suppression of fluorescence and singlet oxygen (1O2) generation of the photosensitizers. Interestingly, this interaction is not predominantly governed by electrostatic interactions but mainly through chemsorptives and physisorptives interactions. Additionally, it was demonstrated that photothermal heating breaks the interaction with the nanostructure, restoring the photophysical properties of the photosensitizer, making this system a multifunctional nanostructure with luminescent and theranostics properties.
Novas abordagens para determinação de melatonina e metabólitos em leite materno e aplicação da metabolômica para fins de diferenciação de cultivares de alface
(Universidade Federal de Goiás, 2024-09-11) Machado, Lucas Santos; Roque, Jussara Valente; http://lattes.cnpq.br/7154037221725381; Chaves, Andréa Rodrigues; http://lattes.cnpq.br/6064014965252121; Chaves, Andréa Rodrigues; Bottoli, Carla Beatriz Grespan; Silva, Bruno José Gonçalves da; Faria, Anízio Márcio de; Sgobbi, Lívia Flório
In analytical chemistry, there is a constant search for methodologies that require less cost and analysis time, but at the same time offer precision and accuracy. In this sense, various methodologies and technologies have been evaluated, among which we can highlight those that employ miniaturized sample preparation techniques and those that use ambient ionization sources for mass spectrometry. This thesis is divided into two chapters presenting the potential of modern sample preparation techniques for liquid chromatography analysis and ambient mass spectrometry analysis. The first chapter describes the use of disposable pipette extraction, utilizing a sorbent phase based on molecularly imprinted polymers (DPX-MIP), for the determination of melatonin and its metabolites (AFMK and AMK) in breast milk by liquid chromatography coupled with mass spectrometry (LC-MS). Different MIPs were synthesized and evaluated for their selectivity in analyzing melatonin and its metabolites, experimentally obtained results were compared with molecular simulation data, showing consistency between the theoretical physicochemical parameters and the experimental data. The application of DPX-MIP in conjunction with LC-MS enabled the development of a method for determining melatonin and its metabolites in breast milk, with recovery values ranging from 87-111% and precision between 2-13%, analysis of patient samples produced values consistent with those reported in the literature. The second chapter explores the application of the paper spray ionization mass spectrometry (PSI-MS) technique to study the metabolomics of lettuce cultivars and the potential differentiation according to their cultivation method and variety. PSI-MS, an ambient ionization technique, uses chromatographic paper as a substrate for the sample ionization process. In this study, lettuce samples were successfully differentiated according to variety and cultivation method through the application of chemometric tools (PARAFAC, PCA, PLS-DA, and OPSDA), identifying 36 metabolites responsible for this differentiation, with choline, mannose, and citric acid being the most influential. Additionally, green chemistry metrics, such as AGREEprep and AGREE, were applied to assess the sustainability of the developed methodologies. The results confirmed that DPX-MIP and PSI-MS are more sustainable, offering appropriate analytical performance with shorter analysis times and generating low volumes of chemical waste
Desenvolvimento de metodologias miniaturizadas de preparo de amostras para a avaliação de pesticidas multiclasses em amostras ambientais
(Universidade Federal de Goiás, 2023-09-05) Martins, Rafael Oliveira; Silva, Bruno José Gonçalves da; http://lattes.cnpq.br/6550581465780888; Chaves, Andréa Rodrigues; http://lattes.cnpq.br/6064014965252121; Chaves, Andréa Rodrigues; Nascentes, Clésia Cristina; Coltro, Wendell Karlos Tomazelli; Hantao, Leandro Wang; Sgobbi, Lívia Flório
The presence of pesticides in the environment is primarily due to the excessive use of these chemical compounds in the global agricultural scenario. In recent decades, the search for new approaches to the analysis and monitoring of these compounds in such matrices has focused on the introduction of sample preparation methodologies as analytical strategies responsible for assessing such complex matrices. Furthermore, the evolution of these sample preparation methodologies over the decades has brought with it the introduction of miniaturized systems capable of overcoming classical challenges faced by conventional sample preparation method-ologies. Thus, this study presents the evaluation of three miniaturized approaches for pesticide extraction in environmental samples. Chapter II presents the development and application of the Hollow Fiber Liquid-Phase Microextraction (HF-LPME) technique for the assessment of 13 multi-class pesticides in soil samples. The methodology reported in the first chapter resulted in R² values >0.98 for all pesticides and detection and quantification limits (LOD and LOQ, re-spectively) in the range of ng L-1 and recovery values between 75.2%-118.8%. The evaluation of the methodology proposed by the AGREEprep software indicated that approximately 70% of the method adhered to the principles of green chemistry adopted by the software. Furthermore, a comparison with classical methods of pesticide extraction in soil identified the HF-LPME method as an efficient approach for monitoring pesticides in soil. Chapter III describes the application of the Electromembrane Extraction (EME) technique for the evaluation of the same set of analytes in soil samples. In this second approach, a special focus was placed on com-paring the proposed method with the one applied in Chapter II, regarding analytical frequency, green aspects, and analytical performance of both methods. Differences were observed in an-alytical aspects, where the EME technique showed higher LOD (76.1 -171.4 μg kg-1) and LOQ (270.7 -516.1 μg kg-1) values than the HF-LPME technique (66.1 -198.1 μg kg-1) and (92.7 -331.2 μg kg-1), respectively. Despite this, values closer to 100% were obtained with the EME technique. A higher analytical frequency was achieved with the EME technique (4 extractions/h) compared to HF-LPME (2 extractions/h). Regarding green chemistry aspects, due to the use of external energy, the methodology proposed by EME showed significant energy consumption. Finally, Chapter IV presented a detailed study of the influence of parameters involved in the on-chip electromembrane extraction technique of the pesticides Carbofuran and Carbendazim in river water samples. This chapter focused on two main aspects: (I)the optimization of the device to reduce leakage during extraction, as it is a disadvantage of the conventional system, and (II)evaluating the differences in the extraction of ionizable and neutral compounds by the on-chip electromembrane extraction system. The optimization of the device introduced the OSTE sealing material as an approach to prevent leaks, allowing for the use of flow rates of 300 μl/min-1 without observing leaks. The evaluation of the parameters involved in the technique showed the dependence of the physicochemical characteristics of the pesticides on the pro-posed system, revealing the extraction of the pesticides in their charged and neutral forms. The analytical evaluation of the method showed LOD and LOQ values ranging from 158.4 to 256.2 μg L-1and 528.1 to 854.1 μg L-1, respectively, and recovery values ranging from 26.3% to 53.8%, indicating an influence of the matrix that was confirmed by the matrix effect study. The study of the pesticides Carbaryl and Carbendazim proved to be an important approach to further expand the field of applications of the on-chip electromembrane extraction technique. The methods described here have proven to be effective analytical strategies for assessing pesticides in en-vironmental samples. The development of the methodologies presented here further expands the possibilities for monitoring pesticides in such complex samples as environmental ones. The application of the proposed methodologies offers a possible strategy for evaluating the effects of these compounds on the environment and proposing ways to identify contaminants in differ-ent environmental compartments.
Síntese de tri-heterociclos pentadienos e estudo de suas propriedades luminescentes
(Universidade Federal de Goiás, 2023-05-09) Matos, Gabriela Ferreira; Kato, Lucilia; http://lattes.cnpq.br/1362891438631386; Kato, Lucilia; Coelho, Felipe Lange; Barros, Olga Soares do Rego; Gonçalves, Pablo José; Santos Neto, José Sebastião dos
This study presents the synthesis of diois (1-4(a-h) and 5, Scheme 1), building blocks commonly used in designing and preparing heteroporphyrins. The synthesis of compounds 1 and 2 has been largely reported in the literature. On the other hand, there are few or no examples of synthetic routes for chalcogen-heteroaryl-substituted compounds such as 3 and 4 (Scheme 1), which constitutes a great challenge. Among the obtained products, thirty-seven molecules are new: five diols, thirty triheteropentadienylmethanes and two porphyrins. Chemical and structural characterization of the compounds 1-4(a-h), 5a and 6 were confirmed through a variety of analytical and spectroscopic techniques: High-Resolution Mass Spectrometry (HRMS), Nuclear Magnetic Resonance (NMR) by 1D and 2D, IR and UV spectroscopy. In addition, X-ray quality single-crystals of 3a allowed the determination of its relative stereochemistry as being (-)-RR-2,5-bis((4-methoxyphenyl)(thiophen-2yl)methyl)thiophene or (-)-SS-2,5-bis((4-methoxyphenyl)(thiophen-2-yl)methyl)thiophene. Unexpected fluorescence emission was observed when compounds triheteropentadienylmethanes were exposed to UV radiation, as shown in Figure 1. The photophysical studies of compounds 2a and 3a revealed a similar absorption profile, with the absorption bands in the violet-to-blue region (between 440-470 nm). Moreover, neither the distinct solvents (ACN, Dioxane, EtOH and CH2Cl2) nor the aryl-substituents (R, Scheme 1) nor the heteroatom (X, Scheme 1) affect significantly the HOMO-LUMO transition energy. In 2a, there is a dependence of the emission wavelength with the excitation wavelength. This fact may indicate that these compounds are examples of molecules exhibiting the non-traditional intrinsic luminescence phenomena.
Sensores miniaturizados para COVID-19 e paracetamol: uma abordagem simples e de baixo-custo
(Universidade Federal de Goiás, 2024-10-09) Moreira, Nikaele Sousa; Coltro, Wendell Karlos Tomazelli; http://lattes.cnpq.br/8302650734477213; Coltro, Wendell Karlos Tomazelli; Souza , Endler Marcel Borges de; Pedrino, Gustavo Rodrigues; Meloni, Gabriel Negrão; Chaves, Andrea Rodrigues
This work describes the development of miniaturized sensors on accessible and low-cost substrates to detect the spike protein (S) of the SARS-CoV-2 virus and paracetamol in whiskey samples. Protein S is a marker associated with COVID-19, which is present on the external part of the virus and has an affinity with the human angiotensin-converting enzyme 2 (hACE2), allowing the infection of human cells. Therefore, its detection is of great importance for an early diagnosis of the disease. In this context, polyester microplates were developed for the colorimetric detection of this protein in biological samples based on a direct ELISA assay for rapid detection and with less use of reagents, in addition to good clinical accuracy. A linear range was obtained in protein S concentrations of 0-10 μg mL-1, with a coefficient of determination (R2) equal to 0.991 and a limit of detection 0.44 μg mL-1. The proposed methodology revealed satisfactory intraplate and interplate repeatability with standard deviation values below 7.7%. Thirty-seven saliva and swab samples from positive and negative patients were evaluated for the presence of the virus. The results were consistent with the RT-PCR method, showing 100% sensitivity and 85.71% specificity for saliva samples. For nasopharyngeal samples, sensitivity was 90% and specificity was 100%. In addition, it revealed diagnostic accuracy above 94%, indicating that the proposed method can predict more than 94% of the samples correctly. Adulteration of whiskey is a common practice in nightclubs due to the high cost of these original drinks. Counterfeiters often add medications or pharmaceuticals to mask the effects of a hangover, for example, paracetamol, as it is an over-the-counter analgesic indicated for the treatment of headaches. Therefore, distance-based detection of paracetamol in whiskey samples using a paper-based microfluidic analytical device (μPAD) is imperative since the use of paper substrate offers excellent benefits, such as accessibility, portability, and the ability to detect paracetamol without expensive instrumentation. Optimal detection conditions were achieved by introducing 5 μL of a mixture containing 7.5 mmol L-1 of Fe(III) and K3[Fe(CN)6] into the detection zone, together with 12 μL of whiskey samples into the sample zone. The method showed linear behavior in the 15 to 120 mg L-1 concentration range, with R2 equal to 0.998. Paracetamol was quantified in spiked samples using the proposed method, and the results were compared with those of a spectrometric method. No significant differences were observed at the 95% confidence level. The method determined approximately 1 drop of the drug paracetamol of 200 mg mL-1 in 1 L of solution, demonstrating excellent sensitivity. Therefore, the proposed methods are alternatives for practical, simple and economical analyses and reduce the consumption of samples, reagents and waste. Then, they have great potential to be used in the field for clinical applications in diagnosing COVID-19 and forensic applications for detecting paracetamol in beverages.
Síntese e Caracterização de Novos Complexos de Ru(III) com Ligantes Nitrogenados Heterocíclicos e Potencial Atividade Antitumoral
(Universidade Federal de Goiás, 2017-05-31) Noronha, Linneker Fernandes de; Souza, Aparecido Ribeiro de; http://lattes.cnpq.br/7884708272070266; Souza, Aparecido Ribeiro de; Quintino, Michelle Pereira; Chagas, Rafael Pavão das
Cancer is a genetic disease caused by mutations in the DNA that can develop in any part of the body. Its treatment follows different approaches, including chemotherapy, which can be quite aggressive. Ruthenium compounds associated with heterocyclic nitrogen ligands have been well studied because of their promising antitumor activity, some of them already present good results and are in the preclinical phase, such as [H-Imidazole] [trans-RuCl4(imidazole)(DMSO)] (NAMI-A) and [H-indazole][trans-RuCl4(indazole)2] (KP1019). In this work, six Ru coordination compounds were synthesized, four of them being unpublished, with heterocyclic nitrogenous ligands 2-(1H-pyrazole)-1-pyridine (L1 ), (1-(pyridine-2)-1H-pyrazole-4-il)methanol (L2 ), ethyl-4-((1-(pyridine-2)-1H-pyrazole-4-il)methyl)pipyrazine-1-carboxylate (L3 ) e 1-(4-((1-(pyridine-2-)-1H-pyrazole-4-)methil)pipyrazine-1-)etanone (L4 ) which are believed to have potential antitumor activity. The compounds were synthesized by reaction under reflux and characterized by: infrared and Uv/Vis spectroscopy, 1H nuclear magnetic resonance spectroscopy, elemental analysis (CHNS), single crystal x-ray diffraction and cyclic voltammetry. The binders used have the same target nucleus for coordination consisting of a pyridine ring and a pyrazole ring. The ligands showed two different modes of coordination to the metal, a bidentate, forming a chelate with the metal, occurs with the ligands L 1 and L 2 and another monodentate, where the ligand coordinates with the metal only by the nitrogen atom of the pyrazole ring, the which occurs with ligands L 3 and L 4 .
Deciphering the stereoselectivity of Claisen rearrangements: joint density functional theory and machine learning models
(Universidade Federal de Goiás, 2024-01-29) Oliveira, Ana Gabriela Coelho; Oliveira, Heibbe Cristhian Benedito de; http://lattes.cnpq.br/ 5995553993631378; Oliveira, Heibbe Cristhian Benedito de; Alonso, Christian Gonçalves; Muniz, Aline Silva; Silveira Neto, Brenno Amaro da; Oliveira, Guilherme Colherinhas de
In the present study, the stereoselectivity of Claisen Rearrangements was addressed, focusing on the influence of two distinct electron-withdrawing groups and eight different substituents in three variants of the rearrangement: Hurd, Eschenmoser, and Johnson. Using the Curtin-Hammett principle, the energies of reactions, products, and transition states were calculated using the M062X/def2TZVPP theory level. The results indicate that kinetic effects predominantly govern the reaction equilibrium. A key aspect of our investigation involved applying Shubin’s energy decomposition analysis to the optimized transition states. This approach highlighted the significant influence of the electrostatic component on stereoselectivity, revealing its predominance over the quantum and steric components. Moreover, each transition state was divided into four fragments: the electron-withdrawing groups (Ester and Nitrile), the specific Hurd/Esch/John group (H, NMe2, and OEt), various substituents (alkyl and aryl), and the central fragment. This fragmentation allowed for a comprehensive analysis of the dipole moments of the groups and non-covalent interactions, providing insights into the electrostatic forces driving the rearrangement process. In addition, Supervised Machine Learning algorithms were employed, focusing on the analysis of electronic and geometric datasets related to the transition states. The results obtained not only elucidate the mechanisms underlying the stereoselectivity of Claisen Rearrangements but also provide a subtle understanding of the interaction between different molecular components, establishing new perspectives in advanced applications in organic synthesis.
Análise de imagens para a determinação de parâmetros de cinética química
(Universidade Federal de Goiás, 2024-05-31) Oliveira, Isabella Moura e; Oliveira, Anselmo Elcana de; http://lattes.cnpq.br/0369339073291948; Oliveira, Anselmo Elcana de; Guimarães, Freddy Fernandes; Coelho, Clarimar José
A low-cost experimental apparatus was built from a video capture device (smartphone) and a lighting box. This system was used to determine the rate constant of fading of Phenolphthalein in NaOH (pH > 10) using video analysis. All computational development was carried out using free software. The analytical methodology developed is statistically equivalent to the determination made by the reference spectrophotometric method (λ = 550 nm). A case study using categorization was designed to evaluate the use of video analysis methodology as a teaching tool in a class on the Experimental Physical Chemistry course. The results obtained reinforce that the methodology developed showed good agreement between the results obtained in the classroom and those in the literature. There was also a positive interest among students in the alternative approach, highlighting the practicality and mobility offered by the new methodology. In other words, this methodology can also be effective in teaching laboratories, especially as a low-cost alternative to the use of UV/Vis spectrophotometers.
Análise de íons inorgânicos em resíduos de explosão utilizando microssistemas eletroforéticos
(Universidade Federal de Goiás, 2018-08-01) Pinheiro, Kemilly Mara Pires; Coltro, Wendell Karlos Tomazelli; http://lattes.cnpq.br/8302650734477213; Coltro, Wendell Karlos Tomazelli; Rosseto, Renato; lonashiro, Elias Yuki
This study describes the development of an analytical methodology based on the use of microchip electrophoresis (MSE) devices integrated with capacitively coupled contactless conductivity detection (C4D) for the separation and detection of inorganic anions in post-blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol L-1 lactic acid, 10 mmol L-1 histidine and 0.070 mmol L-1 cetyl(trimethyl ammonium) bromide. For C4D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 Vpp. The separation of Cl-, NO3-, NO2-, SO42-, ClO4- and ClO3- was performed within ca. 150 s with baseline resolution and efficiencies between 4.4x104 and 1.7x105 plates/m. The found limits of detection ranged between 2.5 and 9.5 μmol L-1. Also, excellent repeatability was obtained, with relative standard deviation lower than 0.8%, 8.8% and 13.5% for the injection time, for the intensity and the peak areas, respectively. Lastly, real samples of post-blast explosive residues were analyzed on the MSE-C4D devices obtaining successfully the determination of Cl-, NO3- and SO42-. The achieved concentration values varied between 2301,610 µg g-1 for Cl-, 805,490 µg g-1 for NO3- and 1453,270 µg g-1 for SO42-. It was also possible to compare the anionic profile of residues of an improved explosive device and a commercial explosive emulsion, confirming the improved explosive device composition, based on ammonium nitrate fuel oil (ANFO). The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the MSE-C4D devices emerge as a powerful and portable analytical platform for on-site analysis demonstrating to be a promising tool for the crime scene investigation.
Determinação de ácidos orgânicos em amostras alimentícias e petroleômicas utilizando sistemas eletroforéticos
(Universidade Federal de Goiás, 2022-06-30) Pinheiro, Kemilly Mara Pires; Coltro, Wendell Karlos Tomazelli; http://lattes.cnpq.br/8302650734477213; Coltro, Wendell Karlos Tomazelli; Vaz, Boniek Gontijo; Lago, Claudimir Lúcio do; Richter, Eduardo Mathias; Micke, Gustavo Amadeu
This study describes the use of microchip electrophoresis coupled to contactless conductivity detection for the determination of inorganic and organic anions for food and petroleomics application. Also, describes the use of capillary electrophoresis coupled to mass spectrometry for petroleomic application. Organic acids are responsible for several wines characteristics, such as aroma, flavor, color and stability. Their analysis are important for monitoring fermentation process and the quality of wines. 12 anions were detected and separated within 100 s, using a buffer composed of 30 mmol L-1 OF 2-(N-Morpholino)ethanesulfonic acid, 15 mmol L-1 of histidine and 0.05 mmol L-1 of cetyltrimethylammonium bromide (pH 5.8). 18 wine samples were analyzed and it was possible to detect and quantify sulfate, phosphate, tartrate, maleate, succinate, acetate and lactate. A multivariate approach was used to investigate the similarities among anionic profile of the wines, and it was possible to discriminate samples mainly by grape varieties, production region and winemaking process. Naphthenic acids are carboxylic acids naturally occurring in crude oil with one or more ring structures. They are present in produced water, which is the water obtained with petroleum during its prospection and are responsible for corrosion, naphthenates deposition, and harmful to the environment when disposed of without treatment. The acids benzoic, 1-naphthoic and 9-anthracenecarboxylic were separated and detected using a microsystem electrophoresis coupled to contactless conductivity detection. The analysis was performed within 140 s using a buffer composed of an equimolar mixture of 10 mmol L-1 of sodium carbonate and bicarbonate (pH 10.2). 5 samples of produced water were analyzed and it was possible to detect and quantify 9-anthracenecarboxylic acid, demonstrating to be an efficient tool for analysis of complex samples matrices for petroleum applications. In this way, electrophoresis microchip proves to be a simple and portable analytical platform for field analysis, proving to be promising for wine quality control and for monitoring the presence of naphthenic acids in produced water samples. A capillary electrophoresis system coupled to a mass spectrometer was also used to analyze naphthenic acids. It was possible to detect cyclopentanecarboxylic acid, benzoic acid, cyclohexanebutyric acid, 1-naphthoic acid, decanoic acid, 3,5-dimethyladamantane-1-carboxylic acid, 9-anthracenecarboxylic acid, pentadecanoic acid and 2-methyl-octadecanoic acid within 13 min using a buffer composed of 40 mmol L-1 of ammonium hydroxide, 32 mmol L-1 of acetic acid and 20% isopropanol (pH 8.6). Produced water samples were analyzed and it was possible to identify and quantify cyclopentanecarboxylic, benzoic, cyclohexanebutyric and decanoic acids. In this way, the proposed method demonstrated to be efficient to detect naphthenic acids analysis in complex samples of produced water using capillary electrophoresis coupled with mass spectrometry. The next steps of this study are the evaluation of other acids in produced water samples for quantification of total acids.
Determinação de escopolamina e butilescopolamina em amostras de bebidas, urina e comprimidos de Buscopan® usando microssistemas eletroforéticos
(Universidade Federal de Goiás, 2023-08-08) Santos, Hellen Inácia dos; Coltro, Wendell Karlos Tomazelli; http://lattes.cnpq.br/8302650734477213; Coltro, Wendell Karlos Tomazelli; Jesus, Dosil Pereira de; Chaves, Andréa Rodrigues
The number of cases in which scopolamine (SCO) was used for both recreational and predatory purposes has increased dramatically in recent decades. Linked to this, there is a concern about obtaining SCO through thermal degradation of butylscopolamine (BSCO) – an active ingredient of Buscopan® – a drug sold without a medical prescription. In this study, mixtures containing SCO and BSCO were separated and detected on a microchip electrophoresis (ME) device with integrated capacitively coupled contactless conductivity detection (C4D) using a running buffer composed of 40 mmol L-1 of butyric acid and 25 mmol L-1 of sodium hydroxide (pH 5.0). The separation was performed within ca. 115 s with a resolution of 1.3 and separation efficiency of 1.4x105 and 1.5x105 theoretical plates m-1 for SCO and BSCO, respectively. The limit of detection was 1.1 μmol L-1 for both species and the developed method revealed satisfactory repeatability with relative standard deviation (RSD) values for forty-eight injections between 4.8 and 9.4% for peak areas and lower than 3.3% for migration times. Furthermore, inter-day precision was evaluated for sixteen injections (a sequence of four injections performed over four days), and RSD values were less than 6.6% for peak areas and 2.2% for migration times. Satisfactory recovery values (95 – 114 %) were obtained for all evaluated beverage samples (cachaça, vodka, whiskey, beer, coke soft drink, and grape juice) as well as for artificial urine samples (95 – 107 %). Finally, the conversion of BSCO into SCO was observed after simple heating procedure of Buscopan® sample (not subject to medical prescription), which was successfully confirmed through analysis by capillary electrophoresis coupled to the mass spectrometry (CE-MS). Based on the reported results, the use of ME-C4D devices has demonstrated a huge potential for applications in the forensic chemistry field.
Manufatura aditiva circular: utilizando e reciclando materiais termoplásticos para desenvolver sensores analíticos
(Universidade Federal de Goiás, 2024-02-05) Silva Neto, Habdias de Araujo; Coltro, Wendell Karlos Tomazelli; http://lattes.cnpq.br/8302650734477213; Coltro, Wendell Karlos Tomazelli; Carrilho, Emanuel; Muñoz, Rodrigo Alejandro Abarza; Janegitz, Bruno Campos; Chaves, Andréa Rodrigues
Additive printing technologies have emerged as powerful tools for the development of portable analytical instrumentation including electrochemical sensors. Before using the device, pre-treatment methods are required to improve the electrochemical performance. Additionally, the additive printing method used thermoplastic polymers that can be harmful to the environment compartments. In this report, we successfully developed five different strategies to manufacture 3D-printed electrodes and have also introduced an initiative for recycling thermoplastic materials in order to create electrodes on paper substrate, contributing to the circular economy. The ecological impact of each proposed method was evaluated also. An activation process was performed by using Fenton's reagents, H2O2 (15%, v/v) and Fe (10 mg L-1 ) in the presence of ultraviolet radiation (5 min), followed by an electrochemical oxidation step in the presence of acetic acid (1.8 V vs C for 200 s). The proposed activation method has used non-toxic reagents and showed excellent improvement in the electrochemical responses with long-term stability (~ 2 months). The manufactured 3D-printed electrodes have exhibited suitable values of limit of detection (at µmol L-1 levels) for different analytes, including metals such as Cd(II) (0.009; 1.01 µg L-1 ) and Pb(II) (0.006; 1.24 µg L-1 ), midazolam maleate (0.54) , uric acid (0.71), adrenaline (0.61), S-nitroso-cysteine (4.1) and folic acid (5.1). In addition, the analytical methodologies described here also demonstrated an excellent ecological profile according to the 12 principles of Green Analytical Chemistry.
Explorando o potencial do CO2 por meio dos líquidos iônicos de fase suportados para produção de carbonatos cíclicos
(Universidade Federal de Goiás, 2024-10-31) Silva, Blendo Almeida da; Chagas, Rafael Pavão das; http://lattes.cnpq.br/9712618482518275; Qadir, Muhammad Irfan; http://lattes.cnpq.br/8517524064523950; Qadir, Muhammad Irfan; Martins, Paulo Roberto; Scholten, Jackson Damiani
The fixation of CO2 into cyclic carbonates is a highly efficient synthetic route, recognized for its atomic economy and wide utility. Ionic Liquids have garnered interest due to their CO2 absorption capacity and chemical stability, making them attractive study targets. This work proposes investigating SILP catalysts for converting epoxides into cyclic carbonates under mild reaction conditions. The catalysts of trichlorozincate of 1-methyl-3-(3- (trimethoxysilyl)propyl)imidazolium, chloride of 1-methyl-3- (trimethoxysilylpropyl)pyridinium, and chloride of 1-methyl-3-(3- (trimethoxysilyl)propyl)imidazolium were synthesized, supported on Al2O3, and characterized by nuclear magnetic resonance, infrared absorption spectroscopy, and thermal analysis. The catalytic study of the SILP-Cl catalyst, it was observed that epoxides containing electron-withdrawing groups in their structure showed the best results, with epichlorohydrin achieving 100% conversion. Additionally, 2-(phenoxymethyl)oxirane (entry 2) and 2-((o-tolyl oxy)methyl)oxirane showed conversion results close to 90%, along with small epoxides like propylene oxide and 1,2-epoxybutane, which also showed satisfactory results. For the SILP-ZnCl3- catalyst, the results were similar to those obtained by the SILP-Cl catalyst, especially under the condition of 100 mg of catalyst and 120°C. Epoxides without this electron-withdrawing effect achieved low conversion values, such as tert-butyl glycidyl ether, which reached around 30% conversion. However, both catalysts maintained high selectivity for cyclic carbonate production. The recyclability tests of the catalyst demonstrated slightly decreased in conversion over four cycles, while maintaining selectivity above 90% without catalyst leaching. The obtained results indicate the efficacy of the established reaction conditions, highlighting the influence of the size and structure of the epoxides on conversion and selectivity.
Propriedades fotofísicas de filmes multicamadas de perovskita livre de chumbo e compostos eletroluminescentes
(Universidade Federal de Goiás, 2024-07-26) Silva, Ramon Miranda; Almeida, Tatiana Duque Martins Ertner de; http://lattes.cnpq.br/9082478597898534; Almeida, Tatiana Duque Martins Ertner de; Colmati Júnior, Flávio; Barbosa, Martin Schwellberger; Talhavini, Márcio; Zalloum, Neife Lilian
Luminescent organic compounds play an essential role in the fabrication of photosensitive active layers, spanning a variety of applications from sensors to lightemitting diodes, photovoltaic systems, among others. In this context, we explored the creation of multilayer films from a hybrid Perovskite (P), with the configuration CH3NH3SnIxCl3-X, combined with recognized electroluminescent compounds such as Rubrene (R), and the polymer Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], MEH-PPV (M), which were deposited by the Layer-by-Layer and spin-coating techniques, and their photophysical properties were studied. Using steady-state and time-resolved fluorescence spectroscopy, it was possible to evaluate the optimal conditions for the production of thin films of the isolated compounds and combinations of interest (bi- and trilayers - P/M; P/R; P/M/R and P/R/M), as well as their photophysical properties. Steady-state electronic spectra demonstrated higher efficiency for films prepared from the deposition of layers of perovskite, Rubrene, and MEH-PPV, using solutions with concentrations of 0.6 – 10-5 and 10-8 mol.L-1, respectively. The layer-by-layer technique involved a 90-second immersion, and spincoating films required 100, 40, and 60 seconds of spin-up rotation for perovskite, Rubrene, and MEH-PPV, respectively. Single point and lifetime mapping analyses, using pulsed lasers (373, 452, and 507 nm), indicated tri-exponential behavior in all evaluations. The results showed for P/R layer-by-layer and spin-coating bilayers excited states with greater sensitivity to the excitation wavelength, prolonging lifetimes with decreasing irradiation length. Mapping analysis indicated regions with higher Eficiência de FRET for P/R when excited at 373 and 452 nm, and for P/M at 507 nm excitation. The Single point data of the Trilayers showed that the inversion in the order of deposition of the semiconductors directly influenced the formation of the system's excited states, with the P/M/R film showing greater sensitivity to the photophysical processes as the excitation length varied. and P/R/M greater stability. Mapping indicated higher FRET rates for P/M/R produced by layer-by-layer, which was selected for UV-Vis sensing studies
Aplicações da cromatografia líquida e espectrometria de massas na análise de contaminantes em amostras de leite bovino e arroz para fins de controle de qualidade e segurança em alimentos
(Universidade Federal de Goiás, 2024-03-28) Soares, Daniel de Almeida; Chaves, Andréa Rodrigues; http://lattes.cnpq.br/6064014965252121; Chaves, Andréa Rodrigues; Rezende, Cintia Silva Minafra e; Lima, Leomir Aires Silva de; Alves, Maria Isabel Ribeiro; Brito, Nubia Natalia De
The present study uses liquid chromatography and mass spectrometry approaches as tools for identifying and quantifying contaminants in foods, such as rice and bovine milk. For the sake of comprehension, this study is divided into four stages: 1) Development of an LC-MS methodology for quantifying the antibiotic ceftiofur in bovine milk samples; 2) Determination of bisphenols (A and S) in long-life milk and its respective packaging by Paper Spray Ionization (PSI-MS); 3) Development of a methodology for determining herbicides in rice (Oryza sativa) samples using the miniaturized hollow fiber liquid phase microextraction sample preparation technique (HF-LPME) with electrospray ionization analysis (ESI-MS); 4) Chemometric analysis comparing rice samples contaminated with fungicides and not contaminated from direct analysis by ESI-MS. In step 1, to determine ceftiofur in milk samples, a liquidliquid extraction (ELL) method was developed followed by analysis of the extracts by LC-MS. The main variables associated with the extraction process were optimized and the figures of merit: linearity, limit of detection and quantification (LOD and LOQ), precision and recovery were evaluated. The method presented LOQ 0.80 ng.mL-1 , inter-day precision of less than 7.3% and recovery greater than 94%. Milk samples obtained from cows subjected to antibiotic application were analyzed for the purpose of evaluating the antibiotic elimination profile in the milk samples. In part 2, it was possible to develop a rapid method for analyzing bisphenols (BPA and BPS) in longlife milk samples and their respective packaging using ambient mass spectrometry using the PSI-MS technique. The method was optimized and the figures of merit linearity, precision, accuracy, LOQ and LOD were evaluated, all of which were within the parameters required by national legislation. The bisphenols under study were detected in all samples (packaging and milk) and in only one sample the BPA content was above 10 ng.mL-1 (maximum residue limit) and for BPS the majority of samples presented levels above the same concentration. In milk, a content of up to 150 ng.mL1 for BPA and an average content of 60 ng.mL-1 for BPS was obtained. The results of this study were published in the journal Food Chemistry (qualis A1). In chapter 3, the use of the miniaturized HF-LPME sample preparation technique followed by ESI ionization mass spectrometry analysis for the determination of herbicides in rice is presented. The main parameters relating to the sample preparation method were optimized, with the use of a two-phase system resulting in shorter extraction times. However, in a three-phase system, with the donor phase at pH 1.7 and the acceptor phase at pH 12, extraction was favored for all analytes. The ionic strength was evaluated by adding salt to the donor solution and did not favor extraction. Therefore, the three-phase system presented a better response to the analytes and the method should have its figures of merit evaluated using the optimized HF-LPME/ESI-MS method. The fourth chapter presents a metabolomic analysis followed by chemometric treatment of data obtained by ESI-MS analysis on rice extract samples using positive and negative modes. A comparison of samples was carried out in 4 different matrices (rice husk, grain with husk, polished grain without husk and unpolished grain without husk). The samples evaluated were divided into two groups: contaminated with fungicides and not contaminated. The data obtained made it possible to separate them into classes using treatments using principal component analysis (PCA). In ESI(-) mode, the data were better explained by PCA Without normalization (89.1%) and also by Quantile Normalization (90%). The negative mode better explains the dissimilarity between the contaminated and uncontaminated rice groups.

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