Navegando por Autor "Leles, Maria Inês Goncalves"
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Item Estudo da estabilidade térmica de óleos de peixes em atmosfera de nitrogênio(2004) Garcia, José Uires; Santos, Harlen Inácio dos; Fialho, Afonso Pereira; Tejerina-Garro, Francisco Leonardo; Antoniosi Filho, Nelson Roberto; Leles, Maria Inês GoncalvesThe fish are a rich source of omega 3 polyunsaturated fatty acids that give benefits to human health beyond basic nutrition. For this reason a lot of studies have been done focusing on the analysis of the content of the substances that compose the foods and the processing effects on foods. These studies have been spread to fishing resources. Many studies about thermal oxidative stability and the kinetic behavior of vegetal oils have been made by Thermogravimetry (TG), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). However, the studies about the oil and fat (from animals) thermal behavior are still lacking. Therefore, on this research analysed the thermal stability of five fish species from Araguaia river (Goiás – Brazil) in a nitrogen atmosphere by TG/DTG. The results showed losses of mass between 235ºC and 490ºC and it points to an equivalence of thermogravimetric behavior between the oils of the five fish species and also between the fish oils and some vegetal oils, such as, araticum, Brazilian wine-palm and palm oils.Item Multiresponse optimization of an extraction procedure of carnosol and rosmarinic and carnosic acids from rosemary(2016) Oliveira, Gerlon de Almeida Ribeiro; Oliveira, Anselmo Elcana de; Conceição, Edemilson Cardoso da; Leles, Maria Inês GoncalvesA green solvent-based optimization for rosmarinic acid (RA), carnosol (COH), and carnosic acid (CA) extraction, the three main antioxidants from rosemary, was performed. The conventional solid-liquid extraction was optimized using a central composite design (CCD) followed by the desirability approach. In the CCD analysis the quantitative effects of extraction time (4.8–55.2 min), liquid-to-solid ratio (4.6–21.4 mL g-¹ ), and ethanol content (44.8–95.2% v/v) were determined for the extracted amount of antioxidants, their concentrations in the extract, and the extraction yield. Samples were analyzed by HPLC and the antioxidants were identified by comparison with pure standard retention times and UV spectra. The desirability function that simultaneously maximizes the antioxidants extraction and their concentrations in the final product was validated. The extraction using a hydroalcoholic solution 70% v/v, at low liquid-to-solid ratio (5 mL g-¹), and after 55-min yielded an antioxidant recovery rate of 89.8%, and a final product 4.75 times richer in the main antioxidants than the raw material.Item Nb2O5 supported catalysts for cross-coupling reactions(2020) Souza, Guilherme Botelho Meireles de; Ribeiro, Thiago Soares Silva; Mourão, Lucas Clementino; Pereira, Mariana Bisinotto; Leles, Maria Inês Goncalves; Liao, Luciano Morais; Oliveira, Guilherme Roberto de; Alonso, Christian GonçalvesPalladium and nickel supported on Nb2O5 were synthesized via wet impregnation method and tested for the Suzuki-Miyaura reaction. The catalysts were characterized by X-ray fluorescence, textural analysis, scanning and transmission electron microscopy, thermogravimetry/differential thermal analysis and X-ray diffraction. Palladium catalyst resulted in high isolated yields (91%). Satisfactory yields (48%) were achieved employing the nickel catalyst. Hot filtration experiments were performed to evaluate the reaction heterogeneity. The catalysts were submitted to consecutive reactions runs to assess recyclability. Deactivation was attributed to catalyst loss by filtration between cycles, minor leaching of the active phase and poisoning by inorganic species.Item Síntese, caracterização e estudo termoanalítico do ftalato, isoftalato e tereftalato de cobalto(2015-12) Carmo, João Paulo Santos do; Leles, Maria Inês Goncalves; Ionashiro, Elias YukiItem Spectroscopy and thermal studies of valsartan compounds with metals Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) in the solid state(2021) Siqueira, Adriana de Paula Cardoso; Ionashiro, Elias Yuki; Bannach, Gilbert; Souza, Aguinaldo Robinson de; Morgon, Nelson Henrique; Soares, Marcos Antônio; Siqueira, Adriano Buzutti de; Leles, Maria Inês GoncalvesSolid-state M-Val compounds were synthesized, where M stands for bivalent metals (Mn, Fe, Co, Ni, Cu, and Zn), and Val stands for valsartanate ion (C24H27N5O32−). The thermal and spectroscopic study of the compounds was performed using TG-DSC, FTIR, DRX, as well as the evolved gas analysis (EGA) by TG/DSC-FTIR. The thermoanalytical results showed information about the stoichiometry of the compounds (1:1), the degree of hydration, and thermal behavior. The EGA results allowed the identification of the aliphatic hydrocarbons, carbon monoxide, carbon dioxide, and ammonia for both Valsartan and metal compounds. The theoretical and experimental spectroscopic data suggested the possible modes of coordination of the ligand with the metal ions by coordinating bonding with the oxygen of the carboxylate and the tetrazole group's nitrogen. The association of Cu (II) and Co (II) metal ions with Val improves the antimicrobial activity against E. coli.Item Study of thermoanalytical behavior of heavier lanthanides terephthalates in air atmosphere(2018-06-04) Costa, Bruna de Araújo; Nunes, Wilhan Donizete Gonçalves; Bembo Filho, Luis Henrique; Siqueira, Adriano Buzutti de; Caires, Flávio Junior; Leles, Maria Inês Goncalves; Ionashiro, Elias YukiCoordination compounds of heavier lanthanides with terephthalate ligand have been synthesized and characterized employing simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), TG coupled to FTIR, elemental analysis and complexometry. The results from complexometry with EDTA and from TG curves allowed to establish the stoichiometry of these compounds, which are in agreement with the Ln2(TFTa)3nH2O general formula where Ln represents trivalent lanthanides or yttrium, TFTA is terephthalate and n = 4 (Er, and Y); 4.5 (Tb, Dy, Ho and Tm); 5 (Yb) and 6.5 (Lu). The thermal decomposition of the anhydrous compounds occurs in two or three consecutive and/or overlapping steps, with the formation of the respective oxides: Tb4O7 and Ln2O3 (Ln = Dy to Lu and Y). The TG-FTIR of the evolved gases obtained from the thermal decomposition of the synthesized compounds, identified the formation of CO2 and water as main gaseous products. The FTIR results also led to information about the type of coordination of the isolated compounds which suggest that the lanthanides are linked to the carboxylate groups by a bridging bond.