Authors:A. Goel, R. Goel, G. Jain Jain, R. Singh Singh, F. Ahmad Ahmad, and G. Singh Singh
A new, specific, sensitive, selective, precise, and reproducible high-performance thin-layer chromatographic (HPTLC) method has been established for study of the stability of 3-acetyl-11-keto-β-boswellic acid (AKBA). HPTLC was performed on aluminium foil plates coated with 200 μm silica gel 60F254. Linear ascending development with toluene-ethyl acetate 7:3 (v/v) was performed at room temperature (25 ± 2°C) in a twin-trough glass chamber saturated with mobile phase vapour. Compact bands (RF 0.52 ± 0.02) were obtained for AKBA. Spectrodensitometric scanning was performed in absorbance mode at 250 nm. Linear regression analysis of the calibration plots showed there was a good linear relationship (r2 = 0.9989 ± 0.0002) between peak area and concentration in the range 200–1200 ng band−1. The method was validated for precision, recovery, robustness, specificity, and detection and quantification limits, in accordance with ICH guidelines. The limits of detection and quantification were 3.06 and 9.29 ng band−1, respectively. The recovery of the method was 99.35–100.21%. AKBA was subjected to various stress test conditions — acid and alkali hydrolysis, oxidation, photodegradation, and dry and wet heat treatment. Degradation products were well resolved from the pure drug with significantly different RF values. Statistical analysis showed the method could be successfully applied for the estimation of AKBA in herbal extract and in nanoparticles. Because the method could effectively separate the drug from its degradation products, it can be regarded as stability-indicating.
Authors:S. Reyes-de Vaaben, A. Aguilar, F. Avalos, and L. Ramos-de Valle
The effect of four nucleating agents on the crystallization of isotactic polypropylene (iPP) was studied by differential scanning
calorimetry (DSC) under isothermal and non-isothermal conditions. The nucleating agents are: carbon nanofibers (CNF), carbon
nanotubes (CNT), lithium benzoate and dimethyl-benzylidene sorbitol.
Avramișs model is used to analyze the isothermal crystallization kinetics of iPP.
Based on the increase in crystallization temperature (Tc) and the decrease in half-life time (τ½) for crystallization, the most efficient nucleating agents are the CNF and CNT, at concentrations as low as 0.001 mass%.
Sorbitol and lithium benzoate show to be less efficient, while the sorbitol needs to be present at concentrations above 0.05
mass% to even act as nucleating agent.
Authors:A. Dumbrava, V. Ciupina, B. Jurca, G. Prodan, E. Segal, and M. Brezeanu
Summary The paper presents the conditions of synthesis and results in the characterization (chemical analysis, thermal analysis, kinetic of decomposition) for two complex compounds of cadmium: [Cd(S2O3)phen]×H2O and [Cd(S2O3)phen2]×2H2O. The obtained complexes were used as precursors for complex sulfides by controlled thermal decomposition. On the basis of transmission electron microscopy (TEM) the complex sulfides may be included in the nanomaterials category.
Nickel ferrite is technologically important magnetic material extensively used in high frequency applications such as microwave
device due to its high resistivity and sufficiently low losses. It also finds application in the ferrofluids technology. Therefore,
ultrafine nickel ferrite was prepared by autocatalytic combustion of novel nickel ferrous fumarato-hydrazinate precursor.
The precursor was characterized by IR, AAS, TG and DTA, and a chemical formula of NiFe2(C4H2O4)3·6N2H4 was fixed. This precursor once ignited with a burning splinter at room temperature, glows and the glow spreads over the entire
bulk completing the autocatalytic combustion of the precursor to ultrafine ferrite. The single phase formation of ultrafine
nickel ferrite was confirmed by XRD, IR spectra and TEM. The average particle size of the ultrafine ferrite was found to be
∼20 nm by TEM. The observed lower value of saturation magnetization for nickel ferrite was due to the superparamagnetic nature
of the particles, which increased with the increasing sintering temperature. The ultrafine nickel ferrite was then sintered
at 1000°C for 5 h and was characterized by XRD, IR spectra, SEM and TEM. The variation of resistivity, Seebeck coefficient
and a.c. susceptibility as a function of temperature was measured for NiFe2O4 and the results are discussed.
Authors:Claudia Messi, P. Carniti, and Antonella Gervasini
A series of catalysts prepared by dispersing iron oxide on supports of different nature and acidity has been studied. Silica
(S) and silica-zirconia mixed oxides (SZ) with different ZrO2 content (from 5 to 45 mass%) were used as supports for the iron oxide phase which was deposited over them by an equilibrium-adsorption
method. The red-ox properties of the Fe-catalysts were studied by temperature programmed reduction (TPR) technique.
The two well defined and narrow TPR peaks observed could be associated with the reduction steps: I) Fe2O3→FeO and Fe2O3→Fe(0) (at ca. 400°C) and II) FeO→Fe(0) (at ca. 800–900°C). The temperature of the second-step-peak increased with the zirconia
content in the support, likely because of the stronger interaction of the iron oxide phase with the support. Activation parameters
for the two step-reduction processes were obtained by a simple computation procedure applied to the TPR profiles.
Authors:Y. Kuroiwa, S. Aoyagi, A. Sawada, H. Ikawa, I. Yamashita, N. Inoue, and T. Atake
The crystal structures of BaTiO3 and PbTiO3 fine particles have been investigated by powder diffraction using synchrotron radiation high energy X-rays. It is revealed
that a BaTiO3 fine particle essentially consists of tetragonal and cubic structure components at 300 K, whereas a PbTiO3 fine particle consists of a tetragonal structure. Adopting a structure model for the BaTiO3 particle that a cubic shell covers a tetragonal core, the thickness of cubic BaTiO3 shell is estimated at almost constant irrespective of particle sizes. Successive phase transitions are detected in 100 nm
particles of BaTiO3 near the phase-transition temperatures of a bulk crystal. The changes in diffraction profiles are small, but they are apparent
for a most up-to-date powder diffractometry.
The thermal decomposition kinetics of nickel ferrite (NiFe2O4) precursor prepared using egg white solution route in dynamical air atmosphere was studied by means of TG with different
heating rates. The activation energy (Eα) values of one reaction process were estimated using the methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS),
which were found to be consistent. The dependent activation energies on extent of conversions of the decomposition reaction
indicate “multi-step” processes. XRD, SEM and FTIR showed that the synthesized NiFe2O4 precursor after calcination at 773 K has a pure spinel phase, having particle sizes of ~54 ± 29 nm.