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  • Author or Editor: Rui Oliveira Macêdo x
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Journal of Thermal Analysis and Calorimetry
Authors: Lidiane Pinto Correia, Elisana Afonso de Moura, Hallisson Meneses Pires, and Rui Oliveira Macêdo

Abstract

Water is a fundamental element of life. Its multiple uses are indispensable for a wide spectrum of human activities. This study aims to characterize water from different salinities obtained in the Cariri region of Paraíba, Brazil. The samples were analyzed using the DSC-coupled to the Peltier system (DSC-Cooling) and physical–chemical water tests performed employing reactive kits, using the Spectroquant Merck® specific for each test. The calorimetric curves showed crystallization phase transitions with different characteristics in peak format and crystallization temperatures between the samples of different salinities. The calorimetric data obtained in the process of crystallization of water is directly correlated to the physico-chemical parameters of conductivity and total dissolved solids, showing that the analytical technology DSC-cooling/heating is suitable for characterization of different salinities water.

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Journal of Thermal Analysis and Calorimetry
Authors: Agna Hélia de Oliveira, Elisana Afonso de Moura, Márcia Ferraz Pinto, José Valdilânio Virgulino Procópio, Valmir Gomes de Souza, Fábio Santos de Souza, and Rui Oliveira Macêdo

Abstract

This work studied the thermal characterization of the pentoxifylline raw material through thermoanalytical techniques (TG, DSC, DSC-photovisual) and analysis of degradation products by Pyr-GC/MS. The picture obtained with DSC-photovisual showed the total vaporization of pentoxifylline at 230.0 °C. The TG dynamical curve presented only one step for the loss of mass evidencing to be a kinetic process of zero order reaction. The pyrograms obtained for pentoxifylline sample in the solid state and solution in the temperatures of 250.0, 300.0, and 400.0 °C, showed only one peak identifying the pentoxifylline.

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Journal of Thermal Analysis and Calorimetry
Authors: José Valdilânio Virgulino Procópio, Valmir Gomes de Souza, Rodrigo Albuquerque da Costa, Lidiane Pinto Correia, Fábio Santos de Souza, and Rui Oliveira Macêdo

Abstract

The simvastatin (SV) is nowadays produced semi-synthetically from lovastatin. It’s one of the statins most commonly used to treat several forms of hypercholesterolemia. This study aimed to apply the thermal characterization of the SV raw material using thermoanalytical techniques and its degradation products by Pyrolysis coupled to Gas chromatography/Mass spectrometry (Pyr-GC/MS). It was studied three samples of SV (SVA, SVB, and SVC). The results showed thermal behavior differences of the samples during the melting process transition and the activation energies (E a) of the thermal decomposition, which were correlated to the thermal stability of them. The first decomposition step of Pyr-GC/MS showed two new compounds of m/z 284 and 207, in proportions dependents according to the pyrolysis temperature.

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Journal of Thermal Analysis and Calorimetry
Authors: Monica Felts de La Roca Soares, José Lamartine Soares-Sobrinho, Keyla Emanuelle Ramos de Silva, Lariza Darlene Santos Alves, Pablo Queiroz Lopes, Lidiane Pinto Correia, Fábio Santos de Souza, Rui Oliveira Macêdo, and Pedro José. Rolim-Neto

Abstract

The ornidazole drug substance presents melt at approximately 90 °C (ΔT = 85–98 °C), which is critical for its use on pharmaceutical manufacturing process. This work aimed the thermal characterization of ornidazole raw-material synthesized by three different manufacturers from India, China, and Italy, using the thermoanalytical techniques of DTA, DSC, and TG, besides the verification of its stability and compatibility as a solid pharmaceutical product by the analysis of its binary mixtures (BM) with excipients and a tablet formulation. The characterization includes the thermal decomposition kinetic investigation by Ozawa model using Arrhenius equation and drug purity determination by Van't Hoff equation. The DSC purity determination and precision were compared with results from UV–Vis spectrophotometric and liquid chromatography, showing an adequate correlation before being recommended as a general method for purity assay. The drug raw-materials presented similar quality and zero-order kinetic behavior, besides showing differences on thermal stability. The drug presented compatibility with the tested excipients since the BM studied presented melting at the same temperature range as the drug and a decomposition temperature similar to the drug for two of the BM, and at a higher temperature for the others three of the BM evaluated, which presented excipients with higher molecular structure, capable of spatial coating on the small drug molecule promoting a physical interaction pharmaceutical acceptable. The tablet was processed by wet granulation and compressed under normal conditions of pressure and temperature, maintaining the physical properties of solid drug approving the manufacturing process used. In this study, the thermal analysis was used with success as an alternative method to characterize, quantify, and perform a preformulation study.

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