Electrospray Ionization Mass Spectrometry (ESI-MS) as a Useful Tool for Fast Evaluation of Anion and Cation Complexation Abilities of a Cyclam Derivative

Electrospray ionization mass espectrometry (ESI-MS) has been used for the study of a cyclam derivative noncovalent interactions. At acidic pH, diprotonated macrocycle bound to different anionic species were observed. The selectivity shown by competitive experiments is rationalized with the help of semiempirical theoretical calculations. At basic pH, the base peak corresponded to the macrocycle-alkaline metal complexes, and again competition experiments showed different binding strength. Finally, experiments carried out in the presence of transition metal salts allowed the detection of the complexes present in the mixture and revealed their different kinetic behavior.     

Study of Nanocrystalline BiMnO3‐‐PbTiO3: Synthesis,Structural Elucidation,and Magnetic Characterization of the Whole Solid Solution

In the last ten years, the study and the search for new multiferroic materials have been a major challenge due to their potential applications in electronic technology. In this way, bismuth‐containing perovskites (BiMO₃), and particularly those in which the metal M position is occupied by a magnetically active cation, have been extensively investigated as possible multiferroic materials. From the point of view of synthesis, only a few of the possible bismuth‐containing perovskites can be prepared by conventional methods but at high pressures. Herein, the preparation of one of these potential multiferroic systems, the solid solution xBiMnO₃‐(1?x)PbTiO₃ by mechanosynthesis is reported. Note that this synthetic method allows the oxides with high x values, and more particularly the BiMnO₃ phase, to be obtained as nanocrystalline phases, in a single step and at room temperature without the application of external pressure. These results confirm that, in the case of Bi perovskites, mechanosynthesis is a good alternative to high‐pressure synthesis. These materials have been studied from the point of view of their structural characteristics by precession electron diffraction and magnetic property measurements.     

Development of an automatic solid phase extraction and liquid chromatography mass spectrometry method by using a monolithic column for the analysis of Cyclosporin A in human plasma

A sensitive and specific and automated liquid chromatography-electrospray mass spectrometric (LC-ESI-MS) assay for the quantification of Cyclosporin A in human plasma was developed. Following a simple protein precipitation step, the supernatant was extracted on-line and directly injected into the system LC-ESI-MS. A relatively new type of monolithic column consisting of a silica rod with bimodal pore structure was used to achieve a retention time of 2.4 min with a very low backpressure at a flow rate of 1 ml/min. The assay was linear from 0.050 to 1.000 μg/ml. The mean recovery was 91%. The mean inter-day and intra-day precisions were 1.85% and 2.83%, respectively. The combination of the automated solid phase extraction and the low retention time achieved with this columns increase the throughput and decrease the time of analysis of each sample. This technology is useful in order to improve the efficiency of the bioanalytical studies.     

Effects of activated carbon properties on the adsorption of naphthalene from aqueous solutions

The aim of this work was to investigate the role of porous and chemical heterogeneities of activated carbons in the adsorption of naphthalene from aqueous media. A commercially available activated carbon was used as the adsorbent, and its surface heterogeneity was systematically altered by heat treatment at 450 and 850 °C, obtaining a series of carbons with various oxygen contents and similar surface functionalities. The results confirmed that the adsorption of naphthalene depends strongly on the pore size distribution of the adsorbent, particularly narrow microporosity. Moreover, oxygen functionalities reduced the accessibility and affinity of naphthalene to the inner pore structure via formation of hydration clusters. Consequently, the hydrophobic/hydrophilic character of the adsorbent is important, since it dominates the competitive adsorption of water. Adsorbents with a high non-polar character (i.e., low oxygen content) have proven to be more efficient for naphthalene adsorption.     

Kinetic models comparison for steam gasification of different nature fuel chars

The reactivity in steam of five different types of solid fuels (two coals, two types of biomass and a petcoke) has been studied. The fuel chars were obtained by pyrolysis in a fixed-bed reactor at a temperature of 1373 K for 30 min. The gasification tests were carried out by thermogravimetric analysis (TG) at different temperatures and steam concentrations. The reactivity study was conducted in the kinetically controlled regime and three representative gas-solid models, volumetric model (VM), grain model (GM) and random pore model (RPM), were applied in order to describe the reactive behaviour of the chars during steam gasification. The kinetic parameters of these models were derived and the ability of the models to predict conversion and char reactivity during gasification was assessed. The best model for describing the behaviour of the samples was the RPM. The effect of the partial pressure of steam in gasification was studied, and the reaction order with respect to steam was determined. The reactivity of the chars was compared by means of a reactivity index. Biomass exhibited a higher reactivity than coals and petcoke. However, significant differences in reactivity were observed between the two types of biomass used, which could be due to catalytic effects.     

A study of oxy-coal combustion with steam addition and biomass blending by thermogravimetric analysis

The thermal characteristics of pulverized coal have been studied under oxy-fuel combustion conditions using non-isothermal thermogravimetric analysis (TG). The atmospheres used were 21%O₂/79%N₂, 21%O₂/79%CO₂, 30%O₂/70%O₂, and 35%O₂/65%CO₂. Coal blends of coal with 10 and 20% of biomass were also studied under these atmospheres. The addition of 10 and 20% of steam was evaluated for the oxy-fuel combustion atmospheres with 21 and 30% of O₂ in order to study the effect of the wet recirculation of flue gas. The results obtained were similar for all the different rank coals and indicated that replacing N₂ by CO₂ in the combustion atmosphere with 21% of O₂ caused a slight decrease in the rate of mass loss and delayed the burning process of the coal, biomass and coal/biomass blend samples. When the O₂ concentration was increased to 30 and 35% in the oxy-fuel combustion atmosphere, the rate of mass loss increased, the burning process occurred at lower temperatures and it was shorter in duration. An increase in the rate of mass loss and a reduction in burning time and temperature were observed after the addition of steam to the oxy-fuel combustion atmosphere. No relevant differences between the 10 and 20% steam concentrations were observed.     

Simultaneous metabolic mapping of different anatomies by 1H HR-MAS chemical shift imaging

Analytical and Bioanalytical Chemistry - Localized information on a specimen is considered indispensable for deciphering biological activity. Magnetic resonance spectroscopy is a notable method...     

In vivo trapping of polyketide intermediates from an assembly line synthase using malonyl carba(dethia)-N-acetyl cysteamines

Early-stage intermediates in the biosynthesis of erythromycin A by Saccharopolyspora erythraea were intercepted by malonyl carba(dethia)-N-acetyl cysteamines, generated in vivo from the hydrolysis of the corresponding methyl esters.     

Relationship between structure and reactivity of carbonaceous materials

Knowledge of the amount and distribution of active sites in carbons is of paramount importance for a better understanding of the kinetics involved in heterogeneous gas solid reactions. In this work a commercial active carbon, CM, was treated at several temperatures in order to obtain a series of samples with different textural and structural properties. The results showed that the loss of reactivity of the samples, determined by thermogravimetric analysis, is related not only to the lower surface area but also to the decrease in the amount of active sites due to a higher structural ordering. This revised version was published online in July 2006 with corrections to the Cover Date.