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Thermal and kinetic study of statins

Simvastatin and lovastatin

Journal of Thermal Analysis and Calorimetry
Authors: M. Souza, Marta Conceição, M. Silva, L. Soledade, and A. Souza

Abstract  

Statins are a group of lipoproteins that are used in medicine to treat the high cholesterol level. The effectiveness of statins in reducing the cholesterol level is significant and in long time scale the reduction of the cholesterol level helps to avoid the incidence of degenerative diseases. Simvastatin and lovastatin are belonging to the ‘statins’ family, one of the pharmacologic groups used in the control of dislipidemy. The objective of this work is the thermal stability and kinetic study of the active forms of simvastatin and lovastatin. Thermal data indicated that lovastatin and simvastatin are stable up to 190 and 170°C in air and up to 205 and 203°C in nitrogen, respectively. For melting temperatures DSC curves showed good correlation with the literature data. Comparing the activation energies of the statins at heating rate of 10°C min–1, lovastatin is more stable than simvastatin under the applied experimental conditions.

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Abstract  

The color efficiency of ceramic glaze blue pigments obtained by the Pechini method was presented in this work. The fired pigments and enameled samples were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), XRD, UV-VIS-NIR spectroscopy and CIE-L*a*b* color-measurements. The pigments obtained by the Pechini method present a better solubility in the molten glazes than the pigments obtained by the mechanical mixture of the precursor oxides.

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Abstract  

The thermogravimetric procedures applied to quality control of foods attain the global analysis of quality of the product, through the determination of quality parameters and the thermal stability of products. The kinetic parameters such as order of reaction, apparent activation energy, pre-exponential factors and the thermal decomposition rate constant were determined for the samples of corn and its derivatives by applying isothermal thermogravimetry, utilizing the Arrhenius law. This method presented excellent results as verified with the coherence and data adjustment. The rate constant values showed the expected performance from the chemical point of view.

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Abstract  

In this work, the influence of attapulgite concentration on the nucleating efficiency of isotactic polypropylene (iPP) and on the kinetics of non-isothermal crystallization were ascertained.The study was conducted by DSC. The nucleating efficiency was determined according to the procedure described by Fillon and the kinetics of non-isothermal crystallization was determined using Ozawa's method using cooling rates of 2, 5 and 10C min−1.Our results indicate that both the relative crystallinity and the crystallization temperature increase with filler content and that a maximum occurs at 2% mass/mass filler content. Both parameters decrease with increasing cooling rates. The Ozawa's exponent tended to increase with temperature and filler content.

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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: C. Xavier, C. Costa, S. Crispim, M. Bernardi, M. Maurera, M. Conceiçăo, E. Longo, and A. Souza

Abstract  

The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor method of ZrO2-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature of 1000C the pigments presented a good thermal stability.

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Abstract  

The high-density polyethylene, thermoplastic widely-used in the production of industrial domestic utilities, was collected in two situations: virgin high-density polyethylene (JV 060) and post-consumption high-density polyethylene (with features of low-density polyethylene). After collecting the samples, they were submitted to natural aging with the quantification of the incident solar radiation for 180 days. The samples were characterized by melt flow index, differential scanning calorimetry, tensile strength, rupture load, elongation at break and infrared. The results showed that after 180 days of exposure the virgin high-density polyethylene presented physical properties similar to the post-consumption polyethylene.

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Journal of Thermal Analysis and Calorimetry
Authors: F. L. Macedo, R. A. Candeia, L. L. M. Sales, M. B. Dantas, A. G. Souza, and M. M. Conceição

Abstract

Searching for other alternative sources, which are not part of the food chain, and which are able to supply the biofuel market is a promising option. In this context, it has been searched to investigate the oiticica oil, approaching its availability to the biodiesel synthesis, as well as its thermal stability. Few works retreat parameters such as: the optimization of the biodiesel synthesis, its physical–chemical properties, and thermal parameters etc. The characterization results revealed that the oil showed very high kinematic viscosity, and acidity value around 13 mg KOH/g, requiring a pre-treatment. To reduce the acid in the oil, it has been done the esterification of oil, which was studied in different molar ratios oiticica oil/ethanol (1:9) and 2.0% catalyst, in order to get the best reduction the index of acidity. The lowest level of acidity of the oil obtained after the esterification was 4.4 mg KOH/g. The reaction rate for the synthesis of biodiesel, compared to the initial mass of oiticica oil ester was 85%. This income can be overcome by pursuing an even smaller reduction of acid value of biodiesel oiticica. The acid value of biodiesel was 1.8 mg KOH/g. The results have revealed that the oiticica oil and biodiesel are stable at 224 and 179 °C, respectively.

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