A highly stereoselective route to substituted bis-tetrahydrofurans from 1,5-dienes.

Bis-tetrahydrofurans $\text{1a}$ and $\text{1b}$, containing four chiral centers, are obtained with a 90 % isomeric purity from geranyl and neryl chlorides in four steps including two stereoselective cyclizations.     

Comparison between GC–MS and GC–ICPMS using isotope dilution for the simultaneous monitoring of inorganic and methyl mercury,butyl and phenyl tin compounds in biological tissues

The aim of this work is to compare simultaneous isotope dilution analysis of organotin and organomercury compounds by gas chromatography–mass spectrometry (GC–MS) and gas chromatography–inductively coupled plasma mass spectrometry (GC–ICP/MS) on certified bivalve samples. These samples were extracted by microwave with tetramethylammonium hydroxide (TMAH). Derivatization with both NaBEt₄ and NaBPr₄ was evaluated, and analytical performances were compared. Two CRM materials, BCR-710 and CRM-477, were analyzed by both techniques to verify accuracy. A mixed spike containing ²⁰¹Hg-enriched methylmercury (MeHg), ¹⁹⁹Hg-enriched inorganic mercury (iHg), ¹¹⁹Sn-enriched monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) as well as homemade ¹¹⁶Sn-enriched monophenyltin (MPT), diphenyltin (DPT), and triphenyltin (TPT) was used for the isotope dilution analysis of samples. The two techniques studied were compared in terms of classic analytical parameters: linearity, precision or repeatability (i.e., percent relative standard deviation, RSD%), limit of detection (LOD), and limit of quantification (LOQ), showing excellent linearity, precision below 12 % for all analytes, and LOQs of 0.06–1.45 pg for GC–MS and 0.02–0.27 pg for GC–ICP/MS.

Matrix-matched quantitative analysis of trace-elements in calcium carbonate shells by laser-ablation ICP–MS: application to the determination of daily scale profiles in scallop shell (<Emphasis Type="Italic">Pecten maximus</Emphasis>)

A micro-scale method has been developed for analysis of trace-element concentration profiles in the calcium carbonate shell of the Great Scallop (Pecten maximus). UV laser ablation at 266-nm coupled with ICP–MS detection was used to analyse daily calcite striae of shell samples to obtain high temporal resolution of trace element incorporation. Analysis of scallop shells was carefully examined to determine the quality of calcium carbonate ablation and calibration. An accurate external calibration method based on matrix matching was developed. Twelve sodium-free enriched calcium carbonate standards containing up to twenty-four elements were prepared, by co-precipitation with aqueous ammonia and NH₄HCO₃, and subsequently back-calibrated in the laboratory. These CaCO₃ standards were found to be homogenous and their use enabled sensitive quantitative analysis (detection limits of a few ng g⁻¹) over a wide range of concentrations (0.1 to 500 μg g⁻¹). Use of these CaCO₃ standards was also evaluated by analysis of three calcium-rich certified reference materials. Because calibration was consistent with the certified results, this analytical method is a sensitive tool for analysis of environmental calcium carbonate matrices. Repeated analysis of scallop shell samples collected simultaneously at the same location showed that the trace elements are homogeneously distributed along a stria. The reliability of such in-situ records of biogenic calcium carbonate (scallop shells) is apparent from the inter-individual and inter-annual reproducibility of the trace element profiles.     

Pollution control and depollution processes by plasma techniques

The European Union is creating strict standards for air and water pollution and waste treatment and implementing aggressive regulations. Compliance with these regulations is impossible without the development of new depollution processes involving plasma or laser technology. Time is one of the major problems in monitoring pollutants with the use of the time-resolution laser-induced breakdown spectroscopy technique, which can perform online analysis without sampling with a high level sensitivity for all the species of the Periodic Table. Plasma-enhanced desorption from fly ashes or polluted soils associated with a mass spectrometer or an optical emission spectrometer allows the monitoring of volatile organic compounds (VOCs) and organochlorine species in a few seconds. In the last DBD point, we present the treatment of VOCs in air by the plasma technique in order to destroy or trap PAH molecules.     

L.D.A. Simultaneous Measurements of Local Density and Velocity Distribution of Particles in Plasma Fluidized Bed at Atmospheric Pressure

Laser Doppler anemometry (L.D.A.) is an efficient and nonintrusive technique. Today, improved in its configuration, the L.D.A. has been applied even in flowing plasmas. ^(1,2) In-flight simultaneous measurements were performed for local density and velocity of particle distribution. The measurements provide an insight into thermal and mass transfer, chemical reactivity, and the distribution of residence times of particles in a plasma fluidized bed. The difficulties of L.D.A. in a plasma fludized bed such as high emission intensity of the plasma torch, high temperature, high particle density, and large distribution of particle granulometry were overcomed in the present investigation. The aims achieved were the characterization of the plasma fluidized bed distribution together with accurate measurements of local particle density and velocity as measured by L.D.A.     

Synthèse de polyéthers polycycliques. 1 Stéréosélectivité de l'hétérocyclisation d'alcools tétrahydrofurfuryliques γ,δ-éthyléniques par les sels mercuriques

The intramolecular oxymercuration of the l-(2-tetrahydrofuryl)4-penten-1-ols (5) by merruric salts followed by reductive demercuration affords the 2-methyl-5-tetrahydrofuryltetrahydrofuran (9) as a mixture of cis and trans isomers in good yields. By using mercuric acetate, each isomier threo 5a and erythro 5b gives the trans isomer, 9d and 9b, respectively, as the major products. On the other hand, cyclizations carried out with mercuric chloride are not stereoselective.     

Modification of the wettability of a poly(ethylene terephthalate) film treated by corona discharge in air

The wettability of poly(ethylene terephthalate) films is an important criterion for their industrial use. The attainment of that property is realized by treatment of the material under corona discharge. The purpose of this article is to describe the influence of the principal parameters of the discharge on the modification of the surface properties; the influence was measured by physicochemical methods (ESCA, contact angle). The results prove that the most important physical parameters of the discharge are the wire-cylinder distance, the current intensity, and the time of treatment. The analysis shows that the fixed species are oxygen and nitrogen in the form of carboxylic functions and amines or nitrogen oxides. In any case, the correlation between free surface energy and concentration of fixed chemical species shows that the surface properties depend on the chemical functions introduced into the material by the discharge.