Use Of Secondary Equilibria For The Separation Of Small Solutes By Field-Flow Fractionation

The dynamic range and selectivity of field-flow fractionation (FFF) can be Increased by using secondary chemical equilibria (SCE). SCE are established by adding a macromolecular additive or aggregate, which strongly Interacts with the field, to the carrier solution. In this study an oil-ln-water (O/W) microemulsion was used as the carrier solution in a sedimentation FFF apparatus. The microemulsion droplets (referred to as the support ) interact with the field and are retained relative to the bulk water. Small solutes that partition or bind to the microemulsion droplets are also retained relative to solutes that do not Interact with the support. In this way It Is possible to separate somewhat polar compounds, such as ascorbic acid and sodium benzoate, which prefer bulk water, from a polar solute, such as toluene, which prefers the support. In addition, the study of retention times in this system allows one to calculate the average microemulsion droplet radius. It appears that SCE-FFF could be a useful way to obtain Important Information on the physicochemical properties of a variety of colloidal supports. © 1988, American Chemical Society. All rights reserved

Theory and Use of the Pseudophase Model in Gas−Liquid Chromatographic Enantiomeric Separations

The theory and use of the “three-phase” model in enantioselective gas−liquid chromatography utilizing a methylated cyclodextrin/polysiloxane stationary phase is presented for the first time. Equations are derived that account for all three partition equilibria in the system, including partitioning between the gas mobile phase and both stationary-phase components and the analyte equilibrium between the polysiloxane and cyclodextrin pseudophase. The separation of the retention contributions from the achiral and chiral parts of the stationary phase can be easily accomplished. Also, it allows the direct examination of the two contributions to enantioselctivity, i.e., that which occurs completely in the liquid stationary phase versus the direct transfer of the chiral analyte in the gas phase to the dissolved chiral selector. Six compounds were studied to verify the model:  1-phenylethanol, α-ionone, 3-methyl-1-indanone, o-(chloromethyl)phenyl sulfoxide, o-(bromomethyl)phenyl sulfoxide, and ethyl p-tolylsulfonate. Generally, the cyclodextrin component of the stationary phase contributes to retention more than the bulk liquid polysiloxane. This may be an important requirement for effective GC chiral stationary phases. In addition, the roles of enthalpy and entropy toward enantiorecognition by this stationary phase were examined. While enantiomeric differences in both enthalpy and entropy provide chiral discrimination, the contribution of entropy appears to be more significant in this regard. The three-phase model may be applied to any gas−liquid chromatography stationary phase involving a pseudophase

The Maunakea Spectroscopic Explorer Book 2018

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.Comment: 5 chapters, 160 pages, 107 figure

French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres

Depletion and voids formation in the substrate during high temperature oxidation of Ni-Cr alloys

A numerical model to treat the kinetics of vacancy annihilation at the metal/oxide interface but also in the bulk metal has been implemented. This was done using EKINOX, which is a mesoscopic scale 1D-code that simulates oxide growth kinetics with explicit calculation of vacancy fluxes. Calculations were performed for high temperature Ni-Cr alloys oxidation forming a single chromia scale. The kinetic parameters used to describe the diffusion in the alloy were directly derived from an atomistic model. Our results showed that the Cr depletion profile can be strongly affected by the cold work state of the alloy. In fact, the oversaturation of vacancies is directly linked to the efficiency of the sinks which is proportional to the density of dislocations. The resulting vacancy profile highlights a supersaturation of vacancy within the metal. Based on the classical nucleation theory, the possibility and the rate of void formation are discussed

Deuterium isotopic exchange on Teicoplanin chiral stationary phase: retention and enantioselectivity

communication par afficheInternational audienc

Centrifugal Partition Chromatography. I. General Features

Centrifugal Partition Chromatography (CPC) is a variant of countercurrent chromatography (CCC). As in CCC, two immiscible liquids are used. The first liquid is the stationary phase, the second is the mobile phase. The liquid stationary phase is held in channels engraved in several polychlorotrifluoroethylene (PCTFE) plates. One hundred channels are engraved on each PCTFE plate. Four PCTFE plates are assembled together in a cartridge. Up to 12 cartridges (4800 channels) can be loaded in the rotor of a centrifuge. The centrifugal field, generated by the spinning rotor, holds the stationary phase sufficiently that a mobile phase can be pumped through it. This system is analyzed in detail. The stationary phase evolution versus time is studied. A complete derivation is made of the relationship linking system pressure to the spin and flow rate as well as to the physicochemical properties of the two liquids, i.e., density and viscosity. Copyright © 1988 by Marcel Dekker, Inc

Centrifugal Partition Chromatography. III. Physico-Chemical Properties Of Ternary Liquid Systems

Four important physico-chemical solvent parameters that affect centrifugal partition chromatography (CPC) were evaluated. They are (i) the mutual solubility of the solvent(s) in each phase which was analyzed using phase diagrams and tie-lines, the results of which can be used to evaluate the behavior and stability of the biphasic CPC system; (ii) solution density which affects the pressure drop; (iii) interfacial tension which affects droplet formation and (iv) viscosity which affects both pressure drop and chromatographic efficiency. These parameters were studied for three ternary solvent systems. The first one had a very low mutual solubility (water-hexane-octanol). The second one had an intermediate mutual solubility (water-hexane-methanol). The last one had a high mutual solubility (water-pentanol-methanol). Copyright © 1988 by Marcel Dekker, Inc