Authors:M. Menezes, E. Pereira Maia, S. Filho, and C. Albinati
In order to assess the elemental concentration level in a galvanizing industry and alert for the need to assess the outcome of a long-term exposure, scalp hair and toenail samples were used as bioindicators and the industry environment was evaluated through airborne particulate matter. The elemental concentration results have pointed out a high exposure to pollutant at workplaces and a high elemental concentration in biomonitors suggesting endogenous contamination. The majority of the elements determined in airborne particulate matter were also determined in hair and toenail samples. The results evidence the efficiency of these matrixes as biomonitors and the importance to carry out the airborne particulate matter sampling in parallel to these biomonitors mainly in occupational epidemiological studies.
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
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.
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
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.
Authors:L. Cides, A. Araújo, M. Santos-Filho, and J. Matos
the present work, the thermal decomposition of glimepiride (sulfonylurea hypoglycemic
agent) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative
thermogravimetry (TG/DTG). Isothermal and non-isothermal methods were employed
to determine kinetic data of decomposition process. The physical chemical
properties and compatibilities of several commonly used pharmaceutical excipients
(glycolate starch, microcrystalline cellulose, stearate, lactose and Plasdone)
with glimepiride were evaluated using thermoanalytical methods. The 1:1 physical
mixtures of these excipients with glimepiride showed physical interaction
of the drug with Mg stearate, lactose and Plasdone. On the other hand,
IR results did not evidence any chemical modifications. From isothermal experiments,
activation energy (Ea)
can be obtained from slope of lntvs. 1/T at a constant
conversion level. The average value of this energy was 123 kJ mol–1.
For non-isothermal method Ea
can be obtained from plot of logarithms of heating rates, as a function of
inverse of temperature, resulting a value of 157 and 150 kJ mol–1,
respectively, in air and N2 atmosphere, from the first
stage of thermal decomposition.
Authors:A. Vasconcelos, M. Dantas, M. Filho, R. Rosenhaim, E. Cavalcanti, N. Antoniosi Filho, F. Sinfrônio, I. Santos, and A. Souza
The influence of drying processes in the biodiesel oxidation was investigated by means of the oxidative induction time obtained
from differential scanning calorimetry data. For this purpose, corn biodiesel was dried by different methods including: chemical
(anhydrous sodium sulfate) and thermal (induction heating, heating under vacuum and with microwave irradiation). The drying
efficiency was evaluated by monitoring IR absorption in the 3,500–3,200 cm−1 range and by the AOCS Bc 2-49 method. In general, the oxidative induction times increased inversely to the heating degree,
except that of microwave irradiation, which was selective to water evaporation and caused low impact over the unsaturation
of biodiesel. The DSC technique was shown to be a powerful tool to evaluate with high level of differentiation the influence
of the drying process on the oxidative stability of biodiesel.
Authors:M. Silva, M. Conceiçăo, M. Trindade, A. Souza, C. Pinheiro1, J. Machado, and P. Filho
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
Authors:L. Lacerda, M. da Silva Carvalho Filho, I. Demiate, G. Bannach, M. Ionashiro, and E. Schnitzler
Corn starch, partially hydrolyzed by fungal α-amylase was investigated by using thermal analysis, microscopy and X-ray diffraction.
After enzymatic treatment lower degradation onset temperatures were observed. DSC analysis showed almost similar range of
gelatinization temperature, however, the enthalpies of gelatinization increased for the partially hydrolyzed starch granules.
According to the X-ray diffraction analysis, stronger cereal pattern peaks were recognized after enzymatic digestion. The
results suggested that the hydrolysis was more pronounced in the amorphous part of the starch granules.
Authors:H. Ouriques, M. Trindade, M. Conceiçăo, S Prasad, P. Filho, and A. Souza
The thermogravimetric curves of di-n-propylammonium, di-iso-propylammonium, di-n-butylammonium and di-iso-butylammonium chlorides showed similar profiles, characterized by mass loss in only one stage, corresponding to decomposition
of compounds. The following thermal stability order was obtained: [Bu2nNH2]Cl>[Pr2nNH2]Cl>[Pr2iNH2]Cl>[Bu2iNH2]Cl. The values of activation energy for non-isothermal data obtained by Ozawa and Coats-Redfern integral methods were in
agreement and stability order obtained by thermogravimetry were reproduced in both methods. The decomposition reactions of
[Pr2nNH2]Cl, [Pr2iNH2]Cl and [Bu2iNH2]Cl were better described by A3 model and [Bu2nNH2]Cl by A2 model.