Authors:G. Souza, I. Pastre, A. Benedetti, C. Ribeiro, and F. Fertonani
Thermogravimetry, Differential Scanning Calorimetry and other analytical
techniques (Energy Dispersive X-ray Analysis; Scanning Electron Microscopy;
Mapping Surface; X-ray Diffraction; Inductively Coupled Plasma Atomic Emission
Spectroscopy and Cold Vapor Generation Atomic Absorption Spectroscopy) have
been used to study the reaction of mercury with platinum foils. The results
suggest that, when heated, the electrodeposited Hg film reacts with Pt to
form intermetallic compounds each having a different stability, indicated
by at least three mass loss steps. Intermetallic compounds such as PtHg4,
PtHg and PtHg2 were characterized by XRD. These intermetallic
compounds were the main products formed on the surface of the samples after
partial removal of bulk mercury via thermal desorption. The Pt(Hg) solid solution
formation caused great surface instability, attributed to the atomic size
factor between Hg and Pt, facilitating the acid solution’s attack to
Authors:I. Pastre, I. do Nascimento Oliveira, A. Moitinho, G. de Souza, E. Ionashiro, and F. Fertonani
The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using
thermogravimetric analysis (TG/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray
diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct
TG and DSC thermal behavior. The fluorescence data of spectra associated to the TG/DT curves allowed to suggest that the 8-HQ
was present in the composites in two different circumstances: 1 - intercalated in the interlayer spaces (Swy-1-8-HQ2), rigidly
associated to the substrate feasible as a monolayer with the aromatic rings parallel to the silica layer; and/or, 2 - adsorbed
on the surface (Swy-1-8-HQ1), either as a bilayer formation or tilting of the molecules to the silicate layer sheet. All results
confirmed above are in agreement with X-ray diffraction patterns, once the interlayer space increases when 8-HQ is incorporated.
The experimental results confirm the formation of the composites in agreement with the method used in the preparation.
Authors:G. Fontanari, J. Batistuti, G. Bannach, I. Pastre, E. Ionashiro, and F. Fertonani
The guava seed protein isolate (PI) was obtained
from the protein precipitation belonging to the class of the gluteline (Ip
4.5). The conditions for the preparation of the PI were determined by both
the solubility curve and simultaneous thermogravimetry-differential thermal
analysis (TG-DTA): pH 11.5, absence of NaCl and whiteners and T=(253)C.
Under these conditions a yield of 77.00.4%, protein content of 94.20.3,
ashes 0.500.05% and thermal stability, T=200C,
were obtained. The TG-DTA curves and the PI emulsification capacity study
showed the presence of hydrophobic microdomains at pH 11.5 and 3.0 suggesting
a random coil protein conformation and, to pH 10.0, an open protein conformation.
The capacity of emulsification (CE), in the absence of NaCl, was verified
for: 1 – pH 3.0 and 8.5, using the IP extracted at pH 10.0 and 11.5,
CE≥3435 g of emulsified oil/g of protein; 2 – pH 6.60 just
for the PI obtained at pH 11.5, CE≥1408 g of emulsified oil/g of
Authors:G. Fontanari, G. Souza, J. Batistuti, V. Neves, I. Pastre, and F. Fertonani
Glutelin, the major protein fraction from guava seed, was obtained by fractioning as described by Osborne. The total proteins
were extracted and the isolates obtained by isoelectric precipitation presented similar DSC curves, concordant with the results
obtained by gel filtration chromatography and electrophoresis in polyacrylamide gel (PAGE-SDS). However, the DSC curves showed
a higher enthalpy with regard to the denaturing protein isolate (PI) extracted at pH 10.0 when compared to a PI at pH 11.5.
Such results are in accordance with those obtained for PI extracted at pH 10.0 using chromatography, this one being present
in the form of molecular aggregates of greater molecular mass. The glutelin fraction, however, did not present a denaturation
peak in the DSC curve, showing that the process for obtaining the same significantly altered its conformation.