Authors:Ana Gomes, Lidiane Correia, Mônica da Silva Simões, and R. Macêdo
The objective of this work was to develop and validate a fast and reproducible method which is able to determine the concentration
of ketoconazole in raw materials and tablets. The samples were analyzed by dynamic thermogravimetry at heating rates of 10,
20, 40, 60 and 80°C min−1 in nitrogen and nitrogen-synthetic air mixture. The concentrations of ketoconazole in the raw material and in the tablets
were obtained from the vapor pressure curves. The data showed that there is no significant difference between the vapor pressure
profiles of ketoconazole itself and in its tablet in both studied environmental conditions confirming that the process is
really vaporization. The concentration of ketoconazole was determined in the raw material and tablets of the drug.
Authors:R. Macêdo, T. Gomes do Nascimento, and J. Veras
This study demonstrates the thermalanalysis applications in compatibility and stability studies of the propranolol binary
mixture sand tablets A and B. The propranolol binary mixtures were prepared in the laboratory and compared to the fully formulated
tablets using the thermogravimetric (TG) and calorimetric(DSC) methods. DSC of binary mixtures showed similar phase transition
to propranolol drug. The tablets phase transition decreased and there was no detectable significant interaction in propranolol–lactose
mixture and tablets. The DSC-photovisual test revealed an interaction similar to the Maillard reaction. The TG isothermal
study showed a difference in the profile between the drug and tablets due excipients quality and problems in manufacture process.
The kinetic parameters indicated a lower stability for the tablets than propranolol drug. The thermal techniques thermally
differentiated the propranolol preparations demonstrating the importance in the design development of pharmaceuticals solid-dosage
Authors:A. de Souza, Fe. Neto, J. de Souza, R. Macedo, J. de Oliveira, and C. Pinheiro
The standard molar enthalpy of formation of crystalline di-isobutyldithiocarbamate complexes of P, As, Sb and Bi(III) has
been derived by solution calorimetry at 298.15 K. The corresponding standard molar enthalpies of sublimation were estimated
by means of differential scanning calorimetry. From the standard molar enthalpies of formation of the gaseous chelates the
homolytic and heterolytic mean metal-sulphur bond-dissociation enthalpies were calculated.
Authors:R. Macêdo, J. Barbosa-Filho, E. da Costa, and A. de Souza
The terpenoids acetyl sitosterol, lupeol, acetyl diosgenin and stigmasterol were studied. Comparison of the thermogravimetric
curves and the activation energies of the terpenoids suggested the following sequence of thermal stability: acetyl sitosterol
< acetyl diosgenin < lupeol < stigmasterol. The DSC curves allowed determination of the melting points and the degrees of
purity. Comparison of the TG and DSC curves revealed the presence of phase transitions without mass loss that were attributed
to rearrangements in the terpenoid molecules.
Authors:Ana Santos, I. Basílio, F. de Souza, A. Medeiros, Márcia Pinto, D. de Santana, and R. Macêdo
Thermal analysis is an essential analytical tool in development of new formulations as well as to study the interaction between
drugs and excipients. This work aims to investigate the possible interactions between metformin and excipients as microcrystalline
cellulose (Microcel MC101®), starch sodium glycolate (Explosol®), sodium croscarmellose (Explosel®), PVP K30, magnesium stearate,
starch and lactose, usually employed in pharmaceutical products. TG, DSC and DTA techniques were used for the thermal characterization
to track if the thermal properties of the drug substance were modified in the mixture. Disregard of the starch and lactose
systems, no changes in thermal behavior of mixtures were found. Thermogravimetric studies (TG) of metformin and its binary
mixtures showed different thermal behavior.
Authors:Rosali Ferreira da Silva, Flávia Morais de Medeiros, T. Nascimento, R. Macêdo, and P. Neto
The object of the present work is to study the thermal characteristics of indinavir sulfate and to evaluate the quality of
the raw materials. Indinavir A, B, C and reference samples were obtained from different suppliers and submitted to TG, DSC
and DSC-photovisual analyses. TG/DTG curves indicated a desolvation and dehydration processes and were confirmed by DSC. According
to the DSC curves the fusion took place at about 141–142°C for indinavir C and Reference sample B and about 146–149°C for
the others. DSC-photovisual showed insoluble raw materials for indinavir C at 160°C. Indinavir sulfate is highly hygroscopic
drug which requires attention during storage and manufacture by pharmaceutical industry.
Authors:Antonilêni Medeiros, Ana Santos, F. de Souza, J. Procópio, Márcia Pinto, and R. Macêdo
Stability of drugs
and products has a great practical interest, which is facing to strict regulation.
Thermal studies, besides the determination of the thermal properties of the
investigated product allow the verification of possible interactions between
the drug substances and excipients. The objective of this work was to obtain
solid pre-formulates of paracetamol (PC) by spray drying (SPDR), as well as
to investigate their thermal behavior. Dynamic and isotherm TG, conventional
DSC and DSC-photovisual coupled methods were used to characterize the conventional
and pre-formulated mixtures obtained by SPDR. The results of both DSC investigations
showed slight alterations in melting temperatures, which suggests incompatibilities.
The TG decomposition data of the mixtures evidenced that the dry process via
SPDR leads to stability enhancement of the pre-formulated mixtures.
Authors:R. Macêdo, T. Gomes do Nascimento, C. Soares Aragăo, and A. Barreto Gomes
The present work reports studies of the thermal behaviour of some anti-hypertensive drugs. Their purities were determined
by DSC and specialized pharmacopeial methods. The activation energy values suggest the following sequence of satability: nifedipine>propanolol
hydrochloride>captoril. Analysis of the DSC data indicated that the degrees of purity of nifedipine, captopril and propanolol
hydrochloride were similar to those found by pharmacopeial methods BP 93 and USP 23. The simplicity, speed and low operational
costs of thermal analysis justify its application in the quality control of pharmaceutical drugs.