A straightforward method for the synthesis of unsymmetrically substituted 1,3-diynes

An efficient synthetic approach to a variety of unsymmetrically substituted conjugated diynes has been developed, starting from the readily available 1,4-bis(trimethylsilyl)-1,3-butadiyne, based upon the selective and sequential substitution of the trimethylsilyl groups with alkyl, aryl and vinyl groups.     

Extraction of molybdenum by a supported liquid membrane method

This is a report on the extraction of molybdenum(VI) ions using a supported liquid membrane, prepared by dissolving in kerosene, the extractant Alamine 336 (a long-chain tertiary amine) employed as mobile carrier. A flat hydrophobic microporous membrane was utilised as solid support. Appropriate conditions for Mo(VI) extraction through the liquid membrane were obtained from the results of liquid-liquid extraction and stripping partition experiments. The influence of feed solution acidity, the carrier extractant concentration in the organic liquid film and the content of strip agent on the metal flux through membrane were investigated. It was established that maximal extraction of metal is achieved at a pH 2.0 if sulphuric acid is used in the feed solution and at a pH value over 11.0 if Na₂CO₃ is used as strip agent. Moreover, the molybdenum extraction through membrane is enhanced when a 0.02 mol l⁻¹ content of the amine carrier in the organic phase is used. The present paper deals with an equilibrium investigation of the extraction of Mo(VI) by Alamine 336 and its permeation conditions through the liquid membrane, and examines a possible mechanism of extraction.     

Iron catalyzed cross-coupling reactions of acyl chlorides with Grignard reagents. A mild,general, and convenient synthesis of aliphatic and aromatic ketones.

Acyl chlorides couple with Grignard reagents at room temperature in the presence of catalytic amounts of tris(acetylacetonate)iron(III), Fe(acac)₃. The reaction is general with respect to both reactants and provides a very mild and convenient method for the synthesis of aliphatic and aromatic ketones.     

Poly(dithiotriethylene adipate): Melting behavior, crystallization kinetics and morphology

The melting behavior and the crystallization kinetics of poly(dithiotriethylene adipate) (PSSTEA) were investigated by differential scanning calorimetry and hot-stage optical microscopy. The observed multiple endotherms, commonly displayed by polyesters, were influenced by the crystallization temperature (T_c) and ascribed to melting and recrystallization processes. Linear and nonlinear theoretical treatments were applied to estimate the equilibrium melting temperature for PSSTEA, using the corrected values of the melting temperature; the nonlinear estimation yielded a higher value by about 15 °C. Isothermal crystallization kinetics were analyzed according to the Avrami’s theory. Values of the Avrami’s exponent n close to 3 were obtained, independently of T_c, in agreement with a crystallization process originating from predeterminated nuclei and characterized by three-dimensional spherulitic growth. As a matter of fact, space-filling spherulites were observed by optical microscopy at all T_c’s. The rate of crystallization became lower as T_c increased, as usual at low undercooling, the crystallization process being controlled by nucleation.     

Effect of solvent composition on signal intensity in liquid chromatography-matrix-assisted laser desorption ionization experiments

The use of reversed phase liquid chromatography for the preparation of complex peptide mixtures for analysis by matrix assisted laser desorption ionization mass spectrometry has led to the observation of the critical importance of the matrix/analyte formulation in regards to the percent organic solvent in the mixture. This paper outlines the study using liquid chromatography to systematically vary the acetonitrile concentration in the formulation used for MALDI spot preparation to examine the impact the parameter has on analyte signal intensity. The results show that for five of six peptides tested across a wide mass range a formulation of approximately 75% acetonitrile is optimal for average MALDI signal intensity as determined on both time-of-flight and quadropole mass spectrometers. Examination of the individual spots shows that the organic solvent content in formulation significantly affects parameters such as crystal density and morphology.     

Vanadium oxide intercalated with polyelectrolytes: novel layered hybrids with anion exchange properties

Novel anion exchange hybrid materials were developed by the insertion of poly(diallymethylammonium chloride) (PDDACl) and poly(allylamine hydrochloride) (PAHCl) polyelectrolytes into V(2)O(5) interlayer spaces using hydrothermal treatment and were used to host an anionic cyanine dye. A systematic study of the hybrid material synthesis by direct in situ reaction of PDDACl and PAHCl polycations with V(2)O(5) powders showed that the interlayer space of V(2)O(5) expands from 0.44 nm to 1.40 nm and 1.80 nm upon intercalation of PDDACl and PAHCl polyelectrolytes, respectively. X-ray photoelectron spectroscopy and DR UV-Vis-NIR spectroscopy revealed that some V(5+) sites were reduced to V(4+) during the intercalation of the polyelectrolytes, these acted as both charge balancing entities for the negative oxide sheets and carriers for exchange sites located in the V(2)O(5) interlayer space. The interlayer separation is consistent with the existence of coiled conformation of the polycations. The hybrid materials produced [PDDACl](0.24)[PDDA](0.29)V(2)O(5) and [PAHCl](0.28)[PAH](0.47)V(2)O(5), exhibited approximately 45.0% and 37.0% of chloride ions still available for anionic exchange, respectively. These materials were used to encapsulate a cyanine anionic dye. The presence of the dye was evidenced in the [PDDACl](0.24)[PDDA](0.29)V(2)O(5) by significant fluorescence, with emission peak centered at 617 nm.     

Pressurized Liquid Extraction Coupled with LC–ESI–MS–MS for the Determination of Herbicides Chlormequat and Mepiquat in Flours

This paper describes a new method for the rapid extraction and unequivocal confirmation of herbicides chlormequat and mepiquat in wheat flours and various flours utilized in infant foods. The highly automated extraction procedure is based on accelerated solvent extraction, followed by liquid chromatography-tandem mass spectrometry as a confirmatory analysis. Typical recoveries from flours and baby food samples ranged from 83 to 99% at a fortification level of 10 ppb, corresponding to the maximum residue limits established by the European Union; while relative standard deviations (RSD) were less than 10% for all samples. The limit of detection (signal-to-noise ratio = 3) of the method for the considered phenols in baby food samples are less than 0.1 μg g^?1. Traces of the selected herbicides have been detected in about 50% of baby foods, bought from different Roman supermarkets and butcher shops, applying the described methodology.     

High- and low-resolution mass spectrometry coupled to liquid chromatography as confirmatory methods of anabolic residues in crude meat and infant foods

Within the European Union the use of anabolic steroids for promoting growth and improving meat-to-fat ratio in food-producing animals has been banned since 1988. For the unequivocal identification of hormone residues in a complex matrix such as meat we have developed a rapid, specific and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method, in combination with a simple extraction procedure based on the matrix solid-phase dispersion (MSPD). The performances of a triple quadrupole (QqQ) and a quadrupole/time-of-flight (QqTOF) were compared: the QqQ mass spectrometer was found to be more sensitive for almost all studied analytes, but the selectivity was superior using the QqTOF system; the full-scan spectra (acquired without losing sensitivity), mass accuracy and resolution of the hybrid instrument enabled a more probatory analyte identification than that obtained selecting two multiple-reaction monitoring (MRM) transitions with a QqQ. Average recoveries ranged from 80 to 100%, and the detection capabilities (CCbetas) were less than 1.06 ppb with the QqQ instrument and less than 5.20 ppb with the QqTOF instrument for the bovine meat, which proved to be the most complex matrix.     

Interaction of “extremely diluted solutions” with aqueous solutions of hydrochloric acid and sodium hydroxide: A calorimetric study at 298 K

The “extremely diluted solutions” (EDS) have revealed a really intriguing behaviour, characterized by multiple independent variables. Because of their behaviour, EDS can be described as far-from-equilibrium systems, capable of auto-organizing as a consequence of little perturbations.

We measured the heats of mixing of basic and acid solutions with such EDS and their electrical conductivity, comparing with the analogous heats of mixing and electrical conductivity of the untreated solvent.

In particular, calorimetric titrations have been performed with NaOH or HCl solutions at various concentrations. Plots of the excess heat as a function of the concentration of titrant reveal differences and similarities between the two. By analysing these plots we were able to formulate new hypotheses about the supramolecular organization of the solvent water, when subject to mechanical perturbations stemming from the EDS preparation protocol, that is comprised of an iterative process of successive dilutions and succussions.