Authors:R. Macêdo, O. de Moura, A. de Souza, and A. Macêdo
This work present comparative results on powder milk storage quality, obtained from analytical methods. Protein content was
determined conventional (Kjeldahl) and colorimetric with biuret reagent at 540 nm and integral quality by thermogravimetric
and biological methods. A method was developed for the protein separation of powder milk. Powder milk was submitted to degradation
processes at 45, 60 and 80°C for 20 days. The results indicated that protein content values were inconsistent if determinations
by Kjeldahl and colorimetric methods and biological tests were compared. There is evidence of thermal decomposition of powder
milk as detected by biological and thermogravimetric methods.
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: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 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: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, 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: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.