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Abstract  

A new formulation of nifedipine tablets was prepared. The tablets were conditioned in amber-colored glass containers and placed in a climatized room at 40 °C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and Thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation products. There is no evidence of interaction between nifedipine and excipients or degradation products. High performance liquid chromatography (HPLC) was used in the dosage of nifedipine tablets before and after acclimatized exposure. Results show that DSC and TG offer important data for a more detailed assessment of the stability of a pharmaceutical formulation.

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Abstract  

A formulation of nifedipine tablets was prepared in the present research. The tablets were conditioned in amber-colored glass containers and placed in a climatized room at 40°C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation products. The results demonstrated that there is no evidence on the interaction between nifedipine and excipients, or degradation products.

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Abstract  

The thermodynamic and kinetic parameters of the thermal decomposition of Zn(S2CNR2)2 complexes (R=CH3, C2H5 and n-C3H7) were determined with the dynamic thermogravimetric method. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions for chelates with R=C2H5 and n-C3H7 occur in the liquid phase, at temperatures far away from their melting points, whereas for the complex with R=CH3 the thermal decomposition begins at a temperature closer to its melting point, suggesting a rather complex decomposition mechanism.

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Journal of Thermal Analysis and Calorimetry
Authors: H. Ouriques, M. Trindade, M. Conceiçăo, S Prasad, P. Filho, and A. Souza

Abstract  

The thermogravimetric curves of di-n-propylammonium, di-iso-propylammonium, di-n-butylammonium and di-iso-butylammonium chlorides showed similar profiles, characterized by mass loss in only one stage, corresponding to decomposition of compounds. The following thermal stability order was obtained: [Bu2 nNH2]Cl>[Pr2 nNH2]Cl>[Pr2 iNH2]Cl>[Bu2 iNH2]Cl. The values of activation energy for non-isothermal data obtained by Ozawa and Coats-Redfern integral methods were in agreement and stability order obtained by thermogravimetry were reproduced in both methods. The decomposition reactions of [Pr2 nNH2]Cl, [Pr2 iNH2]Cl and [Bu2 iNH2]Cl were better described by A3 model and [Bu2 nNH2]Cl by A2 model.

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Abstract  

Thermogravimetry technique is useful to determine the thermal stability of vegetable oils. In this paper some vegetable oils obtained from brazilian Cerrado native plants were studied based on their high oleic acid content. Amburana, baru and pequi pulp oils presented higher yield of extraction compared to soybean oil. The thermal stability of oils in nitrogen was very close hence their fatty acid composition was very similar. Amburana and baru oils have major amount of unsaturated fatty acids, especially linoleic acid and pequi pulp oil has the highest short chain fatty acid content which can explain its lowest thermal stability in synthetic air.

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Summary  

Energy dispersion X-ray fluorescence technique (EDXRF) was employed to study the effects of the fumagina disease through the elementary chemical composition of leaves. The experimental setup consisted of a Mo X-ray tube (Kµ=17.44 keV) with Zr filter and a Si(Li) detector. The measurements were performed with infected and healthy leaves of citric plants. The elements Ti, Mn, Fe, Cu and Zn were quantified. For all the elements of interest the measured detection limit was at the order of mg . g-1.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. P. Felicissimo, J. L. Peixoto, M. S. Barbosa, G. Demortier, J.-J. Pireaux, and U. P. Rodrigues-Filho

Summary  

The purpose of this study was to investigate by PIXE and PIGE the pottery from two archaeological sites located near the Brazil-Bolivia border in Pantanal, an area of natural preservation. The region was inhabited by ancient Amerindian tribes long before the Latin America colonization period and a deep understanding of their environment, cultural attributes and interconnections can only be achieved based on the study of archaeological findings. Multivariate statistical procedures were used to determine similarities and correlations between the analyzed samples and to indicate possible sources of raw material provenience. The results showed that traces of Cr, Cu and Ti and Na/Si and Mg/Si counting ratios were important to distinguish sherds from the archaeological sites MS-CP-71 and MS-CP-61.

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Abstract

Biodiesel has the advantage of being renewable and clean and for these reasons has been studied recently both academically and in industry. Research in this area is focused on developing new synthetic routes to obtain a purer product or to find new alternative sources of food to replace conventional oils. Papaya biodiesel is obtained from oily residues with a fatty acid composition similar to olive oil. It is generally discarded by the ton, considering that Brazil is the world’s largest producer of papaya with an annual output of 1,811 million tons, productivity of 52 t/hectare and domestic consumption at 86.5%. This study was designed by means of thermal analysis (TG, DSC, P-DSC, and MT-DSC), to verify the possibility of achieving high quality biodiesel, with oxidative stability and flow properties previously indicated by composition analysis of its fatty esters, physical–chemical properties (including oxidative stability) using classical methodology, recommended by ASTM D 6756.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Morais, E. da Silva Filho, Oberto da Silva, Maria da Fonseca, Luiza Arakaki, and J. de P. Espínola

Abstract  

Vermiculite with the general formula of [Si6.85Al1.15][Mg4.68Al0.51Fe0.63]O20(OH)4Ca0.128Na0.032K0.094 was made to react with heteroaromatic amines α-, β- and γ-picolines in aqueous solution. The products were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction and thermogravimetry. The intercalated nanocompounds maintained the crystallinity which changed the original interlayer distance of 1422 to 1474, 1456 and 1474 pm, for the sequence of the guest picoline molecules. Thermogravimetry data suggested the intercalation reactions were governed by basicity of amines.

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Journal of Thermal Analysis and Calorimetry
Authors: J. C. O. Santos, M. G. O. Santos, J. P. Dantas, Marta M. Conceição, P. F. Athaide-Filho, and A. G. Souza
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