Inclusion Complexes of Ionic Liquids and Cyclodextrins: Are They Formed in the Gas Phase?

The interaction of imidazolium-based ionic liquids with α- and β-cyclodextrins was investigated by electrospray ionization mass spectrometry with variable collision induced dissociation energy and quantum chemical gas-phase calculations. The center-of-mass energy at which 50 % of a precursor ion decomposes (E_cm,1/2) was determined for the isolated [cyclodextrin + cation]⁺ or [cyclodextrin + anion]^– adduct ions of imidazolium-based ionic liquids with different alkyl chain lengths combined with a large set of anions, such as chloride, bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, dicyanamide, and hydrogensulfate. Moreover, both symmetric and asymmetric imidazolium cationic cores were evaluated. The relative interaction energies in the adduct ions were interpreted in terms of the influence of cation/anion structures and their inherent properties, such as hydrophobicity and hydrogen bond accepting ability, in the complexation process with the cyclodextrins. The trends observed in the mass spectral data together with quantum-chemical calculations suggest that in the gas phase, cations and anions will preferentially interact with the lower or upper rim of the cyclodextrin, respectively, as opposed to what has been reported in condensed phase where the formation of an inclusion complex between ionic liquid and cyclodextrin is assumed.

Influence of Mn on the solidification of Fe–Si–Al alloy for non-oriented electrical steel

Differential scanning calorimetry, thermodynamic calculations, and metallographic analyses were used for a determination of the solidification sequence in a Fe–2.42 %Si–0.5 %Al–0.94 %Mn alloy. For the prediction of the solidification process of the Fe–Si–Al–Mn alloy also a modified Scheil–Gulliver solidification model was used. According to the thermodynamic calculations the two-phase region in the selected Fe–Si–Al–Mn alloy is stable between 1,303 and 913 °C. The highest mass-fraction of the γ-phase is reached at 1,150 °C. With decreasing temperature the austenite retransforms into ferrite. In the temperature range where the thermodynamic calculations predict the existence of the two-phase region in the DSC curves, weak thermal events were observed. A post-exposure metallographic analysis revealed that the substructures in the ferrite microstructure indicate the γ → α phase transformation. This suggests consistency between the differential scanning calorimetry, the thermodynamic calculations, and the metallographic analyses.     

The role of the sol–gel route on the interaction between rhodamine B and a silica matrix

A series of silica xerogels having rhodamine B (RhB) as a template and Ti centers were synthesized by distinct sol–gel routes, namely, acid-catalyzed, base-catalyzed, acid-catalyzed with base-catalyzed (two steps) hydrolytic routes and a FeCl₃-catalyzed non-hydrolytic route. The interaction of RhB with the prepared silica matrix was investigated by Fourier transform infrared spectroscopy, attenuated total reflectance, diffuse reflectance spectroscopy in the ultraviolet–visible region, Raman spectroscopy, mass spectrometry, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and confocal microscopy. Raman spectroscopy suggested the presence of Ti–O and Si–O–Ti moieties within the silica matrix. Infrared band shifts provided insight into potential interaction sites. Taking into account the results from ART, XPS, PL and confocal microscopy, encapsulation of RhB preferentially occurs inside the silica network for acid 1, basic and two-steps routes, and the presence of Ti occurs on the surface of the silica occurs for acid 2, basic and two-steps routes. Also, we have shown that although the structural characteristics of the encapsulated and extracted systems are affected by the route, the molecular structure is conserved during and after the encapsulation process.     

Effect of chromatographic conditions and plasmid DNA size on the dynamic binding capacity of a monolithic support

DNA therapies are becoming recognized alternatives for the treatment and prevention of severe pathologies. Although most current trials have used plasmids <10 kbp, in the future larger plasmids would be required. The purpose of this work was to study the chromatographic behavior of nongrafted carbonyldiimidazole monolithic disks using plasmids with different sizes under hydrophobic conditions. Thereunto, the purification of several plasmids was performed. Higher size plasmids needed lower ammonium sulfate concentration, due to the greater number of interactions between the plasmids and monolith. The dynamic binding capacity experiments for the different plasmids revealed a lower capacity for bigger plasmids. It was also verified that the increase of salt concentration from 2.5 to 3 M of ammonium sulfate increased the capacity. At the highest salt concentration, a slight improvement in the capacity using lower flow rate was observed, possibly due to compaction of plasmid molecules and its better organization on the monolith channels. Finally, a low pH also had a positive effect on the capacity. So, this monolithic support proved to be appropriate to purify the supercoiled isoform of different plasmids with different sizes, providing a valuable instrument as a purification technique.     

An Automated Multi-Pumping Pulsed Flow System with Spectrophotometric Detection for the Determination of Phosphate in Natural Waters

In this work, an automated multipumping pulsed flow system was implemented for the determination of phosphate in natural waters. The developed flow approach was based on the spectrophotometric determination of phosphate by using the vanadomolybdate reaction. The exploitation of a very simple manifold configuration relying on the utilization of just two active components, in this case two solenoid actuated micropumps that were accountable for sample and reagent insertion and commutation, reaction zone formation, and solutions propelling, provided a great operational and optimization simplicity, low reagent consumption, and waste minimization.

Linear calibration plots for phosphate concentrations of up to 20 mg L^?1 (R² = 0.999, n = 6) were obtained, with a detection limit of 0.2 mg L^?1. The sampling rate was about 60 samples per hour. The system was applied to the monitoring of phosphate in local streams at specific sampling stations.     

Application of Alkali Metal Hydroxides for the Preparation of gem‐Chlorophenylcyclopropanes

gem‐Chlorophenylcyclopropanes 3 are conveniently prepared by reaction of benzal chloride (1) with alkenes 2, carried out either in the presence of solid potassium hydroxide and 18‐crown‐6 as a catalyst or cesium hydroxide monohydrate, without solvent.     

Propagation of analyticity for essentially finite -smooth CR mappings

An analytico-geometric reflection principle is established by means of normal deformations of analytic discs.Mathematics Subject Classification (2000): Primary: 32H02. Secondary: 32H04, 32V20, 32V30, 32V35, 32V40