Authors:F. Santos de Souza, A. Gomes Barreto, and R. Macêdo
The present work proposes evaluation of the gelatinization processes of starch by means of DSC coupled with a photovisual
system. The use of DSC, TG and DTA for a fast and efficient evaluation of the starch is suggested. The DSC curves of starch
gels with water contents of 20, 30, 40 and 50% (mass/v) exhibited different phase transitions, corresponding to the gelatinization
processes at the different water contents for the different lots. The DSC-photovisual system confirmed calorimetric behaviour
differences between the starch lots studied.
Authors:A. de Medeiros, N. de Cervantes, A. Gomes, and R. Macêdo
TG and DSC data were used to determine the thermal parameters of prednisone drug and tablets. Two formulations of prednisone
20 mg were analysed in the form of tablets. The TG curves of prednisone drug and tablets A and B displayed six, eight and
seven thermal decomposition processes, respectively. Analysis of the DSC data pointed to chemical interactions between prednisone
drug and the excipients of tablets A and B, suggested by alterations in the melting temperature of prednisone. The analysis
revealed that prednisone drug is more stable than tablets A and B.
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: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: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: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, 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.
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.