GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process.

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Ultrasound-assisted emulsification microextraction coupled with gas chromatography–mass spectrometry using the Taguchi design method for bisphenol migration studies from thermal printer paper, toys and baby utensils

The optimization of a clean procedure based on ultrasound-assisted emulsification liquid-liquid microextraction for the sensitive determination of four bisphenols is presented. The miniaturized technique was coupled with gas chromatography-mass spectrometry after derivatization by in situ acetylation. The Taguchi experimental method, an orthogonal array design, was applied to find the optimal combination of seven factors (each factor at three levels) influencing the emulsification, extraction and collection efficiency, namely acetic anhydride volume, sodium phosphate concentration, carbon tetrachloride volume, aqueous sample volume, sodium chloride concentration and ultrasound power and application time. A second factorial design was applied with four factors and five levels for each factor, 25 experiments being performed in this instance. The matrix effect was evaluated, and it was concluded that sample quantification can be done by calibration with aqueous standards. The detection limits ranged from 0.01 to 0.03 ng mL(-1) depending on the compound. The environmentally friendly sample pretreatment procedure was applied to study the migration of the bisphenols from different types of samples: thermal printer paper, compact discs, digital versatile discs, small tight-fitting waistcoats, baby's bottles, baby bottle nipples of different materials and children's toys.     

Non-Markovianity-assisted steady state entanglement

We analyze the steady state entanglement generated in a coherently coupled dimer system subject to dephasing noise as a function of the degree of Markovianity of the evolution. By keeping fixed the effective noise strength while varying the memory time of the environment, we demonstrate that non-Markovianity is an essential, quantifiable resource that may support the formation of steady state entanglement whereas purely Markovian dynamics governed by Lindblad master equations lead to separable steady states. This result illustrates possible mechanisms leading to long-lived entanglement in purely decohering, possibly local, environments. We present a feasible experimental demonstration of this noise assisted phenomenon using a system of trapped ions.     

Synthesis of Symmetrical and Nonsymmetrical Polyenes by Iterative and Bidirectional Palladium-Catalyzed Cross-Coupling Reactions

Bifunctional unsaturated reagents designed to undergo palladium-catalyzed cross-coupling reactions with complementary polyenyl connective fragments are highly useful for the undoubtedly challenging synthesis of polyenes. The current toolkit of building blocks for the bidirectional formation of Csp²−Csp² single bonds of polyenes includes homo-bisfunctionalized reagents with equal or unequal reactivity (due to steric and/or electronic factors), and hetero-bisfunctionalized counterparts containing either two different nucleophiles, two electrophiles or one of these functionalities and a latent nucleophile that can be unmasked when desired. The combination of these bifunctional linchpin reagents using tactics that modulate the reactivity of each terminus in order to achieve the required connection have streamlined the synthesis of polyenes of great complexity using (iterative) cross-coupling methods for Csp²−Csp² bond formation. Reaction conditions for the Pd-catalyzed cross-coupling reactions are mild and functional-group-tolerant, and therefore these protocols allow to construct the polyene structures using shorter unsaturated reactants with the desired geometries, since in general the products preserve the stereochemical information of the connected cross-coupling partners.     

Hyperfine interaction of ZrO2 — Tetragonal phase

The quadrupole hyperfine interaction of the tetragonal phase of the zirconium oxide has been measured at 1523 K using the time-differential perturbed angular correlation technique. The electric field gradient at zirconium sites was determined to beV _zz =(17.5±0.4)·10¹⁷ Vcm⁻² and axially symmetric.     

TDPAC investigation on thermally related HfF4.3H2O and HfO2

The hyperfine quadrupole interaction of HfF₄.3H₂O at Hf sites is investigated from 14 to 820 K. No transitions have been found. After the complete dehydration of this compound at 393 K, chemical reactions take place which give rise to hafnium oxifluorides and metastable forms of hafnium oxide. Heating treatments at increasing temperatures make HfO₂ turn into its monoclinic phase.     

Photocycloaddition of benzophenone to α-angelicalactone and thermal rearrangement of the product

α-Angelicalactone dissolved in thiophene in the presence of benzophenone was irradiated with uv light in order to find out if the unsaturated lactone behaves either as an olefin capable of yielding a [2 + 2] adduct with the heterocycle or if it rather reacts as a substrate for the excited benzophenone. The isolation of two isomeric oxetanes indicates that the latter is the preferred reaction pathway. One of the oxetanes undergoes an interesting thermal rearrangement.     

A two primers random amplified polymorphic DNA procedure to obtain polymerase chain reaction fingerprints of bacterial species

Polymerase chain reation (PCR) fingerprints are used to characterize and recognize bacteria and are generally obtained using universal primers that generate an array of DNA amplicons, which can be separated by electrophoresis. Universal primers 8F and 1491 R have been used to amplify specifically 16S rDNA. We have used these primers at an annealing temperature of 50 degrees C. Agarose gel electrophoresis of PCR products revealed several bands. The band pattern of each bacterial species was different and the strains belonging to the same species shared an identical pattern. The patterns obtained did not show variations with plasmid DNA content or the growth stage of the bacteria. The peculiarity of the randomly amplified polymorphic DNA (RAPD) described in this work lies in the use of two large primers (proximately 20 nt) to obtain the pattern, since normally a only smaller primer is used, and in the new application for the primers used to amplify 16S rDNA. This new procedure, called two primers (TP)-RAPD fingerprinting, is thus rapid, sensitive, reliable, highly reproducible and suitable for experiments with a large number of microorganisms, and can be applied to bacterial taxonomy, ecological studies and for the detection of new bacterial species.     

Increasing the working calibration range by means of artificial neural networks for the determination of cadmium by graphite furnace atomic absorption spectrometry

Feed-forward artificial neural networks (ANNs), trained with the generalized delta rule, were evaluated for modeling the non-linear behavior of calibration curves and increasing the working range for the determination of cadmium by graphite furnace atomic absorption spectrometry (GFAAS). Selection of this analyte was made on the basis of its short linear range (up to 4.0 μg l⁻¹). Two-layer neural networks, comprising one node in the input layer (linear transfer function); a variable number of neurons in the hidden layer (sigmoid transfer functions), and a single neuron (linear transfer function) in the output layer were assessed for such a purpose. The (1:2:1) neural network was selected on the basis of its capacity to adequately model the working calibration curve in the range of study (0-22.0 μg l⁻¹ Cd). The latter resulted in a nearly six fold increase in the working range. Cadmium was determined in the certified reference material “Trace Elements in Drinking Water” (High Purity Standards, Lot No. 490915) at four concentration levels (2.0, 4.0, 8.0 and 12.0 μg l⁻¹ Cd), which were experimentally within and above the linear dynamic range (LDR). No significant differences (P<0.05) were found between the expected concentrations and the results obtained by means of the neural network. The proposed method was compared with the conventional “dilution” approach, and with fitting the working calibration curve by means of a second-order polynomial. Modeling by means of an ANN represents an alternative calibration technique, for its use helps in reducing sample manipulation (due to the extension of the working calibration range), and may provide higher accuracy of the determinations in the non-linear portion of the curve (as a result of the better fitness of the model).