Evaluation of Sample Preparation Methods for Non-Target Screening of Organic Micropollutants in Urban Waters Using High-Resolution Mass Spectrometry

Non-target screening (NTS) has gained interest in recent years for environmental monitoring purposes because it enables the analysis of a large number of pollutants without predefined lists of molecules. However, sample preparation methods are diverse, and few have been systematically compared in terms of the amount and relevance of the information obtained by subsequent NTS analysis. The goal of this work was to compare a large number of sample extraction methods for the unknown screening of urban waters. Various phases were tested for the solid-phase extraction of micropollutants from these waters. The evaluation of the different phases was assessed by statistical analysis based on the number of detected molecules, their range, and physicochemical properties (molecular weight, standard recoveries, polarity, and optical properties). Though each cartridge provided its own advantages, a multilayer cartridge combining several phases gathered more information in one single extraction by benefiting from the specificity of each one of its layers.     

A fluid mechanical model for granular flow in silos

Granular materials may display both solid and fluid like behaviour. For low densities and high strain rates as in avalanches or during the discharge of silos the behaviour is mainly governed by interparticle collisions. On the other hand, frictional contacts characterise the solid state which is represented within the framework of plasticity theory. A fluid like constitutive model describes granular materials when subjected to large deformations and high strain rates. It bases upon a modified viscoplastic model that is valid for both yielded and unyielded regions. The central idea is the distinction between fluid and solid regions by means of comparing actual shear stress and Coulomb yield stress. The application to the simultion of the discharge of silos shows the feasibility of the chosen method. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Barium antimonide oxide,Ba3Sb2O

The antimonide oxide Ba₃Sb₂O consists of discrete [Sb₂]^4? and O^2? anions, and crystallizes with a new structure type. The Sb—Sb distances are comparable to those known from electron‐precise zintl phases and the tetrahedral coordination of the O^2? anion is also observed in some other Ba‐rich metallide oxides.     

Gemini surfactants: new synthetic vectors for gene transfection

The superior surfactant properties of cationic gemini surfactants are applied to the complex problem of introducing genes into cells. Of almost 250 new compounds tested, of some 20 different structural types, a majority showed very good transfection activity in vitro. The surfactant is shown to bind and compact DNA efficiently, and structural studies and calculations provide a working picture of the "lipoplex" formed. The lipoplex can penetrate the outer membranes of many cell types, to appear in the cytoplasm encapsulated within endosomes. Escape from the endosome--a key step for transfection--may be controlled by changes in the aggregation behavior of the lipoplex as the pH falls. The evidence suggests that DNA may be released from the lipoplex before entry into the nucleus, where the new gene can be expressed with high efficiency.     

Development of an autonomous detector for sensing of nerve agents based on functionalized silicon nanowire field-effect transistors

The ability to detect minute traces of chemical warfare agents is mandatory both for military forces and homeland security. Various detectors based on different technologies are available but still suffer from serious drawbacks such as false positives. There is still a need for the development of innovative reliable sensors, in particular for organophosphorus nerve agents like Sarin.We report herein on the fabrication of a portable, battery-operated, microprocessor-based prototype sensor system relying on silicon nanowire field-effect transistors for the detection of nerve agents. A fast, supersensitive and highly selective detection of organophosphorus molecules is reported. The results show also high selectivity in complex mixtures and on contaminated materials.     

Thermodynamic Methods and Models to Study Flexible Metal–Organic Frameworks

Much attention has recently been focused on a fascinating subclass of metal‐organic frameworks that behave in a remarkable stimuli‐responsive fashion. These soft porous crystals feature dynamic crystalline frameworks displaying reversible, large‐amplitude structural deformations under external physical constraints such as temperature, electric field or gas exposure. The number of reported syntheses of such materials is rapidly growing and they are promising for practical applications, such as gas capture, purification and fluid separation. Herein, we summarize the recently developed thermodynamic tools that can help understand the process of fluid adsorption and fluid mixture coadsorption in these flexible nanoporous materials. These tools, which include both molecular simulation methods and analytical models, can help rationalize experimental results and predict adsorption properties over a wide range of thermodynamic conditions. A particular focus is given on how these methods can guide the experimental exploration of a large number of materials and working conditions (temperature, pressure, composition) to help design efficient processes relying on fluid adsorption in soft porous crystals.     

Ultrasound in synthesis: natural products and supersonic reactions?

Sonochemical syntheses of a number of useful reagents such as samarium diiodide, sodium phenylselenide, tertiary alkoxides and the reducing agent [(PPh₃P)CuH]₆ are discussed. The rates of these sonochemical reactions can be increased by the addition of electron-transfer agents, such as benzophenone ketyls. These results would not be expected on the basis of mechanical effects alone and lend support to proposals that ultrasound acts preferentially on single electron-transfer processes. Ultrasound also allows the rapid and efficient generation of tetracarbonyliron, which can be trapped by simple organic compounds, such as conjugated dienes, vinyl epoxides and allylic alcohols. In the latter cases, this allows the facile preparation of π-allyltricarbonyliron lactone and lactam complexes that can be converted to give a range of biologically active β-, γ- and δ-lactones, including a number of alkaloids and antibiotics. In addition, the δ-lactone products have been incorporated into several complex multi-step syntheses of macrocyclic natural products. The synthesis of key fragments of the potent antiparasitic agent avermectin B1a demonstrates that the sonochemical reaction conditions are fully compatible with the synthesis of highly functionalized molecules.