Fatty acids as chemotaxonomic markers of marine macrophytes from Rio de Janeiro state, Brazil

The distribution of fatty acids in 13 species of macroalgae (Chlorophyta, Ochrophyta and Rhodophyta) and 1 seagrass (Spartina sp), collected on the Rio de Janeiro state coast was determined. The results were evaluated in search of correlations between the taxonomic and phylogenetic position of these macrophytes. Statistical analyses showed the effectiveness as taxonomic and phylogenetic markers of the distribution of the methyl fatty acid esters in these macrophytes.     

Study of the chemical composition of particulate matter from the Rio de Janeiro metropolitan region,Brazil, by inductively coupled plasma-mass spectrometry and optical emission spectrometry

Air quality in the metropolitan region of Rio de Janeiro was evaluated by analysis of particulate matter (PM) in industrial (Santa Cruz) and rural (Seropédica) areas. Total suspended particles (TSP) and fine particulate matter (PM_2.5) collected in filters over 24 h were quantified and their chemical composition determined. TSP exceeded Brazilian guidelines (80 μg m^− 3) in Santa Cruz, while PM_2.5 levels exceeded the World Health Organization guidelines (10 μg m^− 3) in both locations. Filters were extracted with water and/or HNO₃, and the concentrations of 20 elements, mostly metals, were determined by inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectrometry (ICP OES). Water soluble inorganic anions were determined by ion chromatography (IC). To estimate the proportion of these elements extracted, a certified reference material (NIST SRM 1648a, Urban Dust) was subjected to the same extraction process. Concordant results were obtained by ICP-MS and ICP OES for most elements. Some elements could not be quantified by both techniques; the most appropriate technique was chosen in each case. The urban dust was also analyzed by the United States Environmental Protection Agency (US EPA) method, which employs a combination of hydrochloric and nitric acids for the extraction, but higher extraction efficiency was obtained when only nitric acid was employed. The US EPA method gave better results only for Sb. In the PM samples, the elements found in the highest average concentrations by ICP were Zn and Al (3–6 μg m^− 3). The anions found in the highest average concentrations were SO₄^2 − in PM_2.5 (2–4 μg m^− 3) and Cl⁻ in TSP (2–6 μg m^− 3). Principal component analysis (PCA) in combination with enrichment factors (EF) indicated industrial sources in PM_2.5. Analysis of TSP suggested both anthropogenic and natural sources. In conclusion, this work contributes data on air quality, as well as a method for the analysis of PM samples by ICP-MS.     

Secretory cavities and volatiles of Myrrhinium atropurpureum Schott var. atropurpureum (Myrtaceae): an endemic species collected in the restingas of Rio de Janeiro, Brazil

In this study, we investigated the leaf anatomy and the composition of volatiles in Myrrhinium atropurpureum var. atropurpureum endemic to Rio de Janeiro restingas. Particularly, leaf secretory structures were described using light microscopy, and histochemical tests were performed from fresh leaves to localize the secondary metabolites. To observe secretory cavities, fixed leaf samples were free-hand sectioned. To evaluate lipophilic compounds and terpenoids the following reagents were employed: Sudans III and IV, Red oil O and Nile blue. Leaf volatiles were characterized by gas chromatography after hydrodistillation (HD) or simultaneous distillation-extraction (SDE). Leaf analysis showed several cavities in mesophyll that are the main sites of lipophilic and terpenoid production. Monoterpenes, which represented more than 80% of the major volatiles, were characterized mainly by alpha- and beta-pinene and 1,8-cineole. In order to provide tools for M. atropurpureum identification, the following distinguishing characteristics were revealed by the following data: 1) adaxial face clear and densely punctuated by the presence of round or ellipsoidal secretory cavities randomly distributed in the mesophyll; 2) the presence of cells overlying the upper neck cells of secretory cavities; 3) the presence of numerous paracytic stomata distributed on the abaxial leaf surface, but absent in vein regions and leaf margin; and 4) non-glandular trichomes on both leaf surfaces. Our study of the compounds produced by the secretory cavities of M. atropurpureum led us to conclude that volatile terpenoid class are the main secretory compounds and that they consist of a high concentration of monoterpenes, which may indicate the phytotherapeutic importance of this plant.     

Thermal analysis study of the effect of coal-burning additives on the combustion of coals

Thermal analysis is widely used in combustion research for both fundamental and practical investigations. Efficient combustion of coals in cement industry is very important and necessary. In this research, the effects of three coal-burning additives on burning behaviour of bituminous coal and anthracite were studied with the help of thermogravimetry (TG) and differential scanning calorimetric (DSC) analysis. The kinetic study was carried out and the results were presented. The results showed that the coal-burning additives especially LSZ can reduce the ignition temperature, increase the ignition index D _i, combustion ending index D _f and affect the activation energy of the coal samples studied. The coal-burning additives especially LSZ can improve coal combustion effectiveness.     

Thermal analysis study of flavonoid solid dispersions having enhanced solubility

Purposes of this paper were to prepare and study new drug delivery systems for both flavanone glycosides and their aglycones based on solid-dispersion systems. These compounds are poor water soluble drugs, so an enhancement of their dissolution is a high priority. Solid-dispersion systems were prepared using PVP, PEG and mannitol as drug carrier matrices. Characterizations of these dispersions were done by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The glass transition (T_g) temperature of PVP was only recorded in the DSC thermograms of PVP solid-dispersions of both flavanone glycosides and their aglycones, while in case of PEG and mannitol solid-dispersions endotherms of both glycosides and aglycones were noticed with low peak intensity, indicating that high percent of drug is in amorphous state. The XRD patterns of all PVP solid-dispersions of aglycones show typical amorphous materials, but XRD patterns of their glycosides reveal the presence of crystalline material. However, in all solid dispersions shifts in T_g of PVP as well as T_m of PEG were observed, indicating the existence of some interactions between drugs and matrices. SEM and TEM microscopy revealed that PVP/aglycone flavanone compounds are nanodispersed systems while all the other solid dispersions are microcrystalline dispersions. The solubility of both flavanone glycosides and their aglycones was directly affected by the new physical state of solid dispersions. Due to the amorphous drug state or nano-dispersions in PVP matrices, the solubility was enhanced and found to be 100% at pH 6.8 in the nano-dispersion containing 20 mass% of aglycones. Also solubility enhancement was occurred in solid dispersions of PEG and mannitol, but it was lower than that of PVP nano-dispersions due to the presence of the drug compounds in crystalline state in both matrices.     

Thermal study of the fossilization processes of the extinct fishes in Araripe Geopark

The study of fossil materials is very important in the geological and biological researches. They can involve ancient past, evolution or extinction of species, oil prospecting and the understanding of different areas such as: paleoclimate, paleoecology, paleogeography, in addition of climate, environmental changes and life. Araripe Geopark is located in the south area of the Ceará state in the Northeast of Brazil and it provides a general overview of the Earth’s History. In this study the vertebral column extinct fish, Cladocyclus ferox and its nodule from Santana Formation, Northeast of Brazil, calcite and apatite minerals, and vertebral column of recent fish, Opisthonema oglinum were investigated by means of thermal analysis. TG/DTG and DTA curves showed decomposition processes, suggesting water evolution, calcium carbonate and phosphate decomposition and thermal transitions indicated that fossilization processes of fish, carbonaceous material involved the fossil after its death and the organic substance was replaced by inorganic compounds.     

Thermal and kinetic study of nickel trifluoromethanesulphonate,trifluoroacetate and acetate

The reason of comparing thermal behaviour and kinetics of some nickel compounds, is justified by the influence of anion on it, besides supplying information on the stability of the salts. In this work, Ni(TMS)₂·6H₂O, Ni(TFA)₂·3H₂O and Ni(Ac)₂·2H₂O, were synthesized and characterized by microanalysis, atomic absorption molar, conductance and thermal analysis. Thermogravimetric curves indicate that the decomposition of the salts occurs in the range 295–1169 K and the NiO is the final residue. Non-isothermal kinetic evaluation from thermogravimetric data was used to determine energies of activation and pre-exponential factors.     

Thermal analysis study of some transition metal complexes by TG and DSC methods

The thermodynamic and thermal properties of [Cu(L)₂·Cl₂], [Ni(L)₂]·Cl₂, [Co(L)₂·Cl₂]; L=1,2-bis(o-aminophenoxy)ethane (BAFE), complexes have been investigated. The thermal decomposition of the complexes took place in two distinct steps in endothermic reaction up to 700°C. The activation energy E, the entropy change S ^#, enthalpy H change and Gibbs free energy change G ^# were calculated from the results of thermogravimetry analysis (TG) and heat capacity from the results of differential scanning calorimetry (DSC). It was found that the thermal stabilities and activation energies of the complexes follow the order Ni(II)>Cu(II)>Co(II) and E _Co<E _Ni<E _Cu, respectively.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal analysis of mumiyo, the legendary folk remedy from the Himalaya region

Mumiyo is a natural product found mainly in the high mountain ranges of the Himalayas and in some other regions, too. It has been well known as an expensive remedy for a number of diseases for thousands of years. It disappeared completely from the Western medicine and pharmacology, but was frequently used in the former Soviet Union. The present paper concentrates on physical, chemical and microbiological properties of mumiyo, investigated by means of thermal analysis, flow microcalorimetry, capillary electrophoresis, scanning electron microscopy, determination of its natural radioactivity and conventional bioassays with bacteria and fungi. The paper shows that mumiyo is a complex mixture of effective pharmacological substances that acts as a natural bacteriostatic or even bactericidal agent.     

Thermal stability study of the protease inhibitors

A thermal and kinetic analysis of two protease inhibitors: nelfinavir mesylate and atazanavir sulfate, were carried out to find their thermal stability. DSC curves of both drugs showed exothermic transition. This observed process resulted in two steps. Obtained apparent activation energy pointed at low stability of studied protease inhibitors in water solutions.     

DSC analysis of the anti-HIV agent loviride as a preformulation tool in the development of hot-melt extrudates

Thermal analysis was performed on the anti-HIV agent loviride in order to test its suitability to be processed using hot-melt extrusion. Temperature characteristic parameters of crystallization were determined to quantify the stability of amorphous loviride. The present study has shown that cooling and heating loviride at different rates influenced its thermal stability. At high cooling rates melted loviride did not crystallize during cooling, and formed a glass that recrystallized during reheating. Very low cooling rates resulted in significant decomposition of the drug. The glass transition temperature was found to increase as a function of increasing heating rates and the activation energy for the transition from the glassy to the super-cooled liquid state was relatively high, indicating good stability of the glass. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of a potentiometric electronic tongue as a classification tool in food analysis

This paper reports on the application of a potentiometric sensor array to the food analysis field, in order to distinguish simple tastes and to classify food samples. This array is formed by a set of non-specific all-solid-state potentiometric sensors and has been used in combination with principal component analysis (PCA) for the classification of food samples in batch and in flow injection mode. First attempt was to classify synthetic samples prepared with controlled variability. Once this ability is proven, satisfactory classification results are presented for commercial waters, orange-based drinks and tea samples. An interesting correlation is achieved between the natural juice content and its first calculated component, which allows for a very simple tool for screening purposes.     

Thermal analysis and microscopical characterization of cholesterol in gallstones

Summary Cholesterol constitutes the major component of most gallstones. It was identified and determined in gallstones by thermal analysis technique (DSC and TG-DTA), mainly by the use of the melting temperature (T_onset=145°C and T_max=149°C) and by DTG peak decomposition (T_max=364°C). Cholesterol anhydrous (ChA), which showed endothermic polymorphic peak, T_max=40°C, without mass loss, was differentiated from cholesterol monohydrate (ChH), which showed a broad endothermic peak, T_max=59°C, attributed to loss of water of crystallization (theoretical 4.45%). Morphological studies of gallstones were performed by optical microscopy and scanning electron microscopy (SEM). The stones consisted of a pigmented core with a variably-sized irregular central cavity, surrounded by a radially arranged deposits of plate-like ChH. The outer part of the stones showed ChA crystal arborescences. X-ray microanalysis gave a typical spectrum rich in C and O, and in some instances the presence of P, which was attributed to the presence of phospholipids. CaCO₃ was easily characterized by TG with the use of DTG decomposition peak at 674°C.     

Thermal decomposition of two synthetic glycosides by TG,DSC and simultaneous Py-GC-MS analysis

To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the T _p of GLY-A and GLY-B were 254.6 and 275.7°C. The T _peak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively. Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.     

Techniques of thermal analysis applied to the study of cultural heritage

It is increasingly important that chemistry reaches people who have not studied directly this field of science but that, daily, have practices where chemistry is involved in various extents. This is what happens, for instance, in the activities related with the study and the preservation of cultural heritage. In this sense, the present work is a short review of the particular case of techniques based on the thermal analysis and calorimetry applied within the context of the characterization of art and archeological objects, exemplified by various case studies, as the characterization of mortars, preparatory grounds, ancient painting materials and drying oils.     

Thermal lens spectrometry as a tool for determination of stability constants of complex compounds

The potential of thermal lens spectrometry in the determination of stability constants of complex compounds was explored using copper(I) and iron(II) complexes with 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline as examples. Thermal lens spectrometry offers advantages over conventional spectrophotometry in the determination of stability constants both in aqueous and nonaqueous media. The overall and stepwise stability constants of iron(II) tris(1,10-phenanthrolinate), copper(I) bis(2,9-dimethyl-1,10-phenanthrolinate), and copper(I) bis(1,10-phenanthrolinate) were determined at levels as low as 10⁻⁸–10⁻⁶ mol L⁻¹.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 123–133, January, 2005.     

Thermal analysis of some polynuclear coordination compounds as precursors of iron garnets (M3Fe5O12, M=Y3+ or Er3+)

The thermal behaviour of four coordination compounds (NH₄)₆[Y₃Fe₅(C₄O₅H₄)₆(C₄O₅H₃)₆]·12H₂O, (NH₄)₆[Y₃Fe₅(C₆O₇H₁₀)₆(C₆O₇H₉)₆]·8H₂O, (NH₄)₆[Er₃Fe₅(C₄O₅H₄)₆(C₄O₅H₃)₆]·10H₂O and (NH₄)₆[Er₃Fe₅(C₄O₆H₄)₆(C₄O₆H₃)₆]·22H₂O has been studied to evaluate their suitability for garnet synthesis. The thermal decomposition and the phase composition of the resulted decomposition compounds are influenced by the nature of metallic cations (yttrium-iron or erbium-iron) and ligand anions (malate or gluconate).     

Thermal analysis at the evaluation of concrete damage by high temperatures

Summary Concrete damage by high temperatures includes mass loss, strength and modulus reductions and the formation of cracks and large pores. Thermal treatment reduces the amount of chemically bound water in the hydrate phase. With a rise in temperature, the spatial distribution of Ca(OH)₂ crystals becomes more compact; smaller crystals occur in a unit volume of the cement paste. A rise in temperature affects the pore structure by reducing the specific surface of hydration products. Cement paste becomes more heterogeneous in microstructure and coarser in pore structure. Compressive strength is not only significant parameter showing structural integrity of concrete; permeability influences concrete durability as well. To demonstrate this, permeability coefficients at various high temperatures are presented. The key quantitative insight into the hydrate phase behavior is based on thermal analysis results. Thermogravimetric (TG) mass losses are related to the phase changes represented either by DTA or DTG. Based on these, the tests employing TG mass losses and related DTA and DTG curves answer the question if the hydrate phase is present at individual high-temperature levels and what its quantitative state is. Method of thermal analysis is suitable for the interpretation of concrete behavior when subjected to high-temperature attack. Conclusions are drawn about thermal stability and residual properties of concrete specimens made at the construction site of Mochovce nuclear power plant (Slovakia); and subjected to temperatures up to 800°C. Relations among mechanical properties, permeability, pore median radius and bound water content in concrete are discussed and evaluated.     

Theory of Emanation Thermal Analysis: XI. Radon diffusion as the probe of microstructure changes in solids

The theoretical background for the use of radon diffusion as a probe of microstructure changes in solids is given. The high sensitivity of the emanation thermal analysis (ETA) in the study of solid state processes especially interactions taking place on surfaces and in the near surface layers is described. The increasing sensitivity of the method towards bulk processes with rising temperature is theoretically shown. The background considerations to be used in the mathematical modeling of temperature dependences of the radon release from solids on heating (i.e. simulated ETA curves) are presented. Various models for radon diffusion and various functions describing the annealing of structure irregularities, which served as diffusion paths for radon, were used in the modeling. It was shown, that ETA is able to characterize microstructure changes in the surface layers of the thickness from several nanometers to several micrometers.This revised version was published online in November 2005 with corrections to the Cover Date.     

Application of thermal analysis in study of binary mixtures with metformin

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.