New insights for materials science characterisation using different complementary techniques combined with x-ray absorption spectroscopy

The combination of x-ray absorption spectroscopy (XAS) with UV-Vis and Raman spectroscopies or with Differential Scanning Calorimetry (DSC) has been recently carried out on the D44 beamline of DCI-LURE. The different set-ups used to perform such combinations are described and examples of combined investigations belonging to different field of materials science (coordination chemistry, sol-gel and catalysis) are presented. © Physica Scripta 2005.

Relationships between the curing conditions and some mechanical properties of hybrid thermosetting materials

The relationship between the heat of polymerization (ΔH) and activation energy (Ea) parameters, obtained by differential scanning calorimetry (DSC) and the ratio of epoxy resin to hardener of the thermosetting materials based on an organic-inorganic hybrid epoxy resin (OG) was investigated. Activation energy (Ea) and heat of polymerization (ΔH) increased with an increasing OG content, up to 70 wt%. Further increase in OG content to 80wt% reduced Ea and ΔH. Dynamic mechanical analysis indicates that the maximum cross-link density is obtained at 83 wt% OG, whereas fracture toughness and tensile modulus mechanical properties are maximized at 70 wt% OG. ©2006 Sociedade Brasileira de Química.

Inclusion complex of S(-) bupivacaine and 2-hydroxypropyl- β-cyclodextrin: Study of morphology and cytotoxicity

Local anesthetics (LA) belong to a class of pharmacological compounds that attenuate or eliminate pain by binding to the sodium channel of excitable membranes, blocking the influx of sodium ions and the propagation of the nerve impulse. S (-) bupivacaine (S(-) bvc) is a local anesthetic of amino-amide type, widely used in surgery and obstetrics for sustained peripheral and central nerve blockade. This article focuses on the characterization of an inclusion complex of S(-) bvc in 2-hydroxypropyl-β-cyclodextrin (HP-β-CD). Differential scanning calorimetry, scanning electron microscopy and X-Ray diffraction analysis showed structural changes in the complex. In preliminary toxicity studies, the cell viability tests revealed that the inclusion complex decreased the toxic effect (p<0.001) produced by S(-) bvc. These results suggest that the S(-) bvc:HP-β-CD inclusion complex represents a promising agent for the treatment of regional pain.

Methanol oxidation on PtRu/C electrocatalysts prepared by a microemulsion method

PtRu/C nanocatalysts were prepared by a microemulsion method using different values of water/surfactant molar ratio in order to get different particle sizes. Crystallite sizes and structural properties were determined by X-ray diffraction. Particle size and distribution were characterized by transmission electron microscopy and average composition was determined by energy dispersive X-ray analysis. Differential scanning calorimetry measurements indicated the presence of oxides in the as-prepared catalysts. The general electrochemical behavior was evaluated by cyclic voltammetry in 0.5 M sulfuric acid and the electrocatalytic activity towards the oxidation of methanol was studied in 0.5 M methanol acid solutions by potential sweeps and chronoamperometry. copyright The Electrochemical Society.

Protocolo para ensaios físico-químicos de estabilidade de fitocosméticos

The growing demand for stable, safe and effective cosmetics has required increasingly complex studies by the scientific community and the use of more efficient techniques to determine the stability of these products. The use of active principles from the Brazilian flora has led to the development of numerous products, in the most varied pharmaceutical forms, making it, even more difficult to standardize experimental protocols to certify the stability of cosmetic preparations. While in Brazil there is no one protocol that standardizes the tests that should be carried out to determine product stability, several studies have been conducted in academic laboratories to determine the stability of specific raw materials. The rheological properties of topical use products have to be taken into account in their manufacture, storage and application. The determination of the rheological behavior of a formulation helps in evaluating the physicochemical nature of the vehicle, allowing early signs of physical instability to be detected and thus enabling quality control of the constituents, test formulations and final products. Thermal analysis has also been used to assist in the study of cosmetic stability and differential scanning calorimetry to guide the development of new products. Other tools, such as fluorimetry and laser granulometry can be used to help the study and development of both emulsified and non-emulsified systems. The aim of the present study is to develop a protocol for the investigation of the physical and chemical stability of phytocosmetics - systems containing active compounds extracted from the Brazilian biodiversity.

Sistemas biodegradáveis contendo acetato de prednisolona para administração orbitária

Purpose: The present study aimed to evaluate an injectable extended-release formulation of prednisolone acetate (PA) for orbital administration. Methods: Microspheres (MEs) of poly-ε-caprolactone (PCL) containing PA were developed by the method of solvent evaporation. The MEs obtained were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), encapsulation efficiency and in vitro release profile. The in vivo release profile was evaluated in rabbits after periocular injection of an aqueous suspension of MEs. The local biocompatibility of the system was verified by histopathologic analysis of the deployment region. Results: After MEs preparation, morphological analysis by SEM showed the feasibility of the employed method. The content of PA encapsulated was 43 ± 7% and can be considered as satisfactory. The system characterization by DSC technique, in addition to confirm the system stability, did not indicate the existence of interaction between the drug and the polymer. The in vitro release study showed the prolonged-release features of the developed system. Preliminary in vivo study showed the absence of local toxicity and confirmed the prolonged release profile of PA from MEs, suggesting the viability of the developed system for the treatment of orbital inflammatory diseases. Conclusion: The results obtained in this work are relevant and accredit the system developed as a possible alternative to the treatment of inflammatory orbitopathy.

Analytical model for heterogeneous crystallization kinetics of spherical glass particles

An analytical model developed to describe the crystallization kinetics of spherical glass particles has been derived in this work. A continuous phase transition from three-dimensional (3D)-like to 1D-like crystal growth has been considered and a procedure for the quantitative evaluation of the critical time for this 3D-1D transition is proposed. This model also allows straightforward determination of the density of surface nucleation sites on glass powders using differential scanning calorimetry data obtained under different thermal conditions. © 2009 The American Ceramic Society.

Thermal studies of chitin-chitosan derivatives

New poly(azo) amino-chitosan compounds were obtained from the azo coupling reaction of N-benzyl chitosan and diazonium salts. The thermal behavior of these compounds was studied by thermogravimetric analysis (TG), differential thermogravimetric analysis (DTG), TG coupled with a Fourier-transform infrared, and differential scanning calorimetry (DSC). TG/DTG curves of chitin-chitosan polymer showed two thermal events attributed to water loss and decomposition of the polysaccharide after cross-linking reactions. Thermal analysis of the poly(azo) amino-chitosan compounds showed that the decomposition temperatures decreased when compared to the starting chitin-chitosan and N-benzyl chitosan. DSC results showed an agreement with the TG/DTG analyses. Thermal behavior of poly(azo) amino-chitosans suggest that these compounds could be considered as potential thermal sensors. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Synthesis, characterization and thermal study of solid mandelate of some bivalent transition metal ions in CO2 and N2 atmospheres

Solid state M-L, where M stands for bivalent transition metals (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) and L is mandelate, were synthesized. Simultaneous thermogravimetry and differential scanning calorimetry, elemental analysis and complexometry were used to establish the stoichiometry and to study the thermal behaviour of these compounds in CO2 and N2 atmospheres. The results show that all the compounds were obtained in the anhydrous state and in agreement with the general formula ML2. The thermal decomposition of the compounds occurs in a single (Cu(II)), two (Ni(II)) three (Fe(II), Co(II)), four (Mn(II)) and five (Zn(II)) steps. The results also provided information concerning the ligand's denticity, thermal behaviour, final residues and identification of gaseous products evolved during the thermal decomposition of these compounds. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Thermal and spectroscopic studies of solid oxamate of light trivalent lanthanides

Solid-state LnL3·1.25H2O compounds, where L is oxamate and Ln is light trivalent lanthanides, have been synthesized. Simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), experimental and theoretical infrared spectroscopy, TG-DSC coupled to FTIR, elemental analysis, complexometry, and X-ray powder diffractometry were used to characterize and to study the thermal behavior of these compounds. The results led to information about the composition, dehydration, thermal stability, thermal decomposition, and gaseous products evolved during the thermal decomposition of these compounds in dynamic air atmosphere. The dehydration occurs in a single step and through a slow process. The thermal decomposition of the anhydrous compounds occur in a single (Ce), two (Pr), and three (La, Nd to Gd) steps with the formation of the respective oxides, CeO2, Pr 6O11, and Ln2O3 (Ln = La, Nd to Gd). The theoretical and experimental spectroscopic study suggests that the carboxylate group and amide carbonyl group of oxamate are coordinate to the metals in a bidentate chelating mode. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Thermal behavior of lignin and cellulose from waste composting process

The lignin and cellulose were extracted from reference material (leaves and twigs) and food of compost at different times composting: zero (raw), 30, and 120 days. According to thermogravimetric analysis and its derivative and differential scanning calorimetry curves for these samples, were verified during composting process there were considerable changes in its thermal profiles, as well as, characteristics lignin in cellulose samples and cellulose in lignin samples. These features were found by fourier transformed infrared spectroscopy. © 2012 Akadémiai Kiadó, Budapest, Hungary.

The thermal, rheological and structural properties of cassava starch granules modified with hydrochloric acid at different temperatures

Starch is arguably one of the most actively investigated biopolymer in the world. In this study, the native (untreated) cassava starch granules (Manihot esculenta, Crantz) were hydrolyzed by standard hydrochloric acid solution at different temperatures (30 °C and 50 °C) and the hydrolytic transformations were investigated by the following techniques: simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), as well as non-contact atomic force microscopy (NC-AFM), X-ray diffraction (XRD) powder patterns, and rapid viscoamylographic analysis (RVA). After the treatment with hydrochloric acid at different temperatures, the thermal stability, a gradual loss of pasting properties (viscosity), alterations in the gelatinization enthalpy (ΔHgel), were observed. The use of NC-AFM and XRD allowed the observation of the surface morphology and topography of the starch granules and changes in crystallinity of the granules, respectively. © 2012 Elsevier B.V. All rights reserved.

Thermal behavior of some antihistamines

Thermogravimetry (TG), differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM), as well as X-ray powder diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR) were used to study the thermal behavior and the chemical structure of cimetidine, famotidine, ranitidine-HCl, and nizatidine. The TG-DSC curves show that the famotidine and ranitidine-HCl suffer decomposition during melting and they are thermally less stable in comparison with cimetidine and nizatidine, the latter being the most stable of all the drugs studied in this study. The DSC curves of famotidine and ranitidine-HCl show exothermic peaks immediately after the melting, confirming the occurrence of thermal decomposition. The DSC curves also show that the cimetidine and nizatidine have some thermal stability after melting. The thermal events shown in the PLTM images are consistent with the results shown in the TG-DSC and DSC curves. The XRD patterns show that the cimetidine and famotidine are less crystalline compared with ranitidine-HCl and nizatidine. The theoretical FTIR bands are in agreement with those obtained experimentally, and in some cases, no difference is observed between the theoretical and experimental values, even being identical in one of the cases. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Synthesis, characterization and thermal behavior of solid state compounds of heavy trivalent lanthanide succinates

Solid-state Ln-L compounds, where Ln stands for heavy trivalent lanthanides or yttrium(III) (Tb-Lu, Y) and L is succinate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-DTA coupled to FTIR, elemental analysis, X-ray powder diffractometry and complexometry were used to characterize and study the thermal behavior of these compounds. For the terbium to thulium and yttrium compounds, the dehydration, as well the thermal decomposition of the anhydrous compound occurs in two consecutive steps, while ytterbium and lutetium the dehydration occurs in a single step. The results also led to information about the ligand's denticity, thermal stability and thermal decomposition of these compounds. © 2013 Elsevier B.V.

Thermal behaviour of α-hydroxyisobutyric acid, sodium α-hydroxyisobutyrate and its compounds with some bivalent transition metal ions

Synthesis, characterization and thermal decomposition of bivalent transition metal α-hydroxyisobutyrates, M(C4H7O 3)2·nH2O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as the thermal behaviour of α-hydroxyisobutyric acid and its sodium salt were investigated employing simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), infrared spectroscopy (FTIR), TG-DSC coupled to FTIR, elemental analysis and complexometry. All the compounds were obtained as dihydrated, except the copper one which was obtained in the anhydrous state. The thermal decomposition of the anhydrous compounds occurs in a single or two steps and the final residue up to 235 C (Mn), 300 C (Fe), 305 C (Co), 490 C (Ni), 260 C (Cu) and 430 C (Zn) is Mn2O3, Fe2O3, Co3O 4, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity and identification of the gaseous products evolved during the thermal decomposition of these compounds. Copyright © 2013 Published by Elsevier B.V. All rights reserved.