L X-ray production cross sections, average L shell fluorescence yield and intensity ratios in heavy elements

L X-ray fluorescence cross sections, and intensity ratios were measured for elements in the 70￡Z￡92 atomic range at the excitation energy 59.5 keV using a Si(Li) detector. Furthermore, L X-ray fluorescence cross sections and intensity ratios were calculated for elements in the same range. The average L shell fluorescence yields were derived using experimental L X-ray fluorescence cross sections and theoretical photoionization cross sections. The obtained results were compared with other experimental and theoretical values. This revised version was published online in August 2006 with corrections to the Cover Date.     

New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid-molecular solvent mixtures

The low vapor pressure and the versatility of the physico-chemical properties of ionic liquids make them really attractive as an alternative for conventional molecular solvents. The knowledge of their physico-chemical properties (viscosity, conductivity, miscibility with organic solvents and anion-cation interactions) has appeared mandatory for better targeting their applications, although it is generally still lacking or incomplete.This work promotes capillary electrophoresis instrumentation as an integrated apparatus for measurement of viscosity, conductivity and absorbance of pure ionic liquids and ionic liquid-molecular solvent mixtures. Compared to current conventional techniques, the assets of this instrumentation for this purpose are the combined availability of a pressure delivery system, power supply, diode array absorbance detector and thermoregulation device, allowing unattended, automatic and easy operation, involving minimum sample handling. Most importantly, the required sample volume can be reduced to about 50 μL, making this protocol very cost-effective. A protocol was optimized with respect to time, sample consumption and data reliability for the determination of these physico-chemical parameters. Ionic liquids selected for method development and validation differed in the nature of their cation (butyl- and ethyl-methylimidazolium) and anion (trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide). Various molecular solvents were mixed with these ionic liquids (acetonitrile, methanol, dimethylformamide and trifluoroethanol) and the same physico-chemical properties were determined by optimized methods. The knowledge of these data should be of great support in various application areas, including the development of new separation media for capillary electrophoresis and chromatographic techniques.     

Oligomérisation anionique de l'ethylène. I. Etude cinétique

A kinetic study of ethylene oligomerization in hexane, in the presence of n-BuLi–TMEDA complexes, allowed us to suggest a new mechanism for anionic ethylene oligomerization. n-BuLi and n-Bu(CH₂CH₂)Li species have the same reactivity. The RLi–TMEDA complex in a 1-to-1 stoichiometry is the active species. The following kinetic equation has been established: It reflects the intervention of associated species (n-BuLi–TMEDA)₂ as well as the influence of the concentration of the complexing agent on the kinetics of oligomerization.     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

Additional of functional vinylzinc reagents to nitrones: synthesis of (E)-N-allylhydroxylamines and their rearrangement into (E)-O-allylhydroxylamines

The vinylzinc reagents derived from hydrozirconation of alkynes and transmetallation add readily to nitrones to yield pure (E)-N-allylhydroxylamines; some of these rearrange into O-allylhydroxylamines.