E. Tronel-Peyroz

Lasalocid (X537A) as a selective carrier for Cd(II) in supported liquid membranes

The carboxylic antibiotic lasalocid was shown to facilitate the transport of Cd(II) cations through supported liquid membranes, the driving force being the proton gradient between the two aqueous phases. With hydrocarbons as solvents inside the porous support, the initial metal fluxes were linear versus the inverses of the viscosity values, in accordance with a diffusion limited mechanism. With the polar solvent nitrophenyl octyl ether, the initial flux was six times higher than expected from the viscosity value, and up to 95% of the metal ions were transported. In competitive experiments with equal initial Cd(II) and Zn(II) concentrations, after 94% of Cd(II) had been transported the ratio of Cd(II) to Zn(II) in the receiving phase was 3.8 (pH 8.2 in the source phase, pH 2 in the receiving phase, membrane impregnated with lasalocid 5×10−3 M in nitrophenyl octyl ether).

A study of the interfacial behavior of polyoxyethylene at a mercury—aqueous solution interface: Compact and diffuse layers

Abstract The adsorption of polyoxyethylene (POE) at a mercury-solution interface has been studied, using NaF, KF, and KCl as supporting electrolytes and polymers over a molecular weight range from 400 to 4000. In the first part, a flat configuration of the adsorbed macromolecule is put forward from an analysis of data concerning three characteristic properties of the adsorbed layer. In the second part, information on the diffuse layer in the presence of a saturated layer of POE is obtained from experiments at various salt concentrations. While the classical models of Gouy-Chapman (GC) and Stern-Grahame for the diffuse and global double layer are well verified for concentrations higher than 10−2 M, a deviation from the theoretical expectation is found for more dilute solutions, increasing with the absolute value of the surface charge. It seems difficult to interpret this effect in terms of an artifact due to the experimental techniques or to solution impurities. Similar deviations from the GC model are expected in the case of electrophoretic measurements. A comprehensive explanation is not given but the results show that it is related to the particular nature of the double layer in the presence of polymer.

On the influence of the adsorbent, the hydrophobic, and the oxyethylenic chain lengths on nonionic surfactant adsorption

Abstract A discussion of previously published results concerned mainly with adsorption of copolymers of the type CmH2m+1O(CH2CH2O)pH as a function of m (including m = 0), p, and of the adsorbent is reported. The maximum surface excess and the corresponding molecular area could be determined only from the experiments. The results taken as a whole can be explained by a two-state adsorption model, the former state being determined by hydrophobic interactions and the latter by specific interactions between the surface and the hydrophilic tail. The ratio of the adsorption equilibrium constants corresponding to each state is determined by comparison between the predictions of the model and the available data, this ratio varies according to m and temperature. Differences from some conclusions on the results previously reported are pointed out. Some implications of the information derived from this work are discussed.

High performance two-dimensional gel electrophoresis using a wetting agent Tergitol® NP7

Two‐dimensional electrophoresis is an efficient method for the analysis of a broad range of complex protein samples. Current two‐dimensional gel techniques are not suited for analysis of the small amount of proteins from tissue samples in the presence of high concentration of salts. Here we describe an improved two‐dimensional gel electrophoresis procedure based on the use of a nonionic wetting agent, Tergitol® NP7, in rehydration solution combined with the application of a linear potential sweep during isoelectrofocusing. This experimental approach yields a dramatic increase in the resolution and focusing of proteins visualized on two‐dimensional gels. This technique is less time‐consuming and laborious than the current techniques and can be used for a variety of two‐dimensional electrophoresis applications, including proteome analysis.

Impedance and electrical potential across supported liquid membranes: role of interfacial potentials on the active transport of a metal cation

Abstract The facilitated transport mechanism of a metal cation across a supported liquid membrane was examined in the case of a Cd 2+ flux mediated by the natural ionophore lasalocid; the polypropylene membrane was impregnated with o -nitrophenyl octyl ether. Impedance and membrane potential measurements were carried out along with flux measurements of the Cd 2+ /H + counter transport. A proton flux was inferred from the membrane potential measurements performed under open circuit, zero electrical current, conditions. This proton flux was confirmed by impedance measurements performed under closed circuit, non-zero electrical current, conditions. The main consequence of this proton transfer under open circuit conditions (which are the normal membrane separation conditions) was the building of interfacial potentials. These potentials modify the ionic concentrations at the membrane interfaces, and thus render invalid the mathematical treatment of the cation flux based on the equilibrium ion exchange concept which is generally used. When the potential dependence of the effective interfacial reactions is incorporated into the transport model, the theory can account quantitatively for the experimental fluxes measured under open circuit conditions.

Wetting transitions and other wetting properties of water–2,5 lutidine system

The wetting behavior of the water–2,5 lutidine system has been studied around the lower consolute point (Tc=13.1 °C). We have measured contact angles and surface tensions by varying the concentration and temperature. In the diphasic region, a wetting transition has been observed at 46–47 °C on a silica wall by direct observation of the solid–liquid–liquid contact angle. The perfect wetting occurs close to Tc, the wetting phase is water rich. At the liquid–vapor interface, the analysis of the values of the surface tensions shows that, close to Tc, they obey critical laws and that a lutidine rich phase perfectly wets the vapor and the water rich phase. These behaviors have been analyzed on the basis of the contact angles of the monophasic on a silica wall on both sides of the coexistence curve, and the general variation of the surface tensions. A second wetting transition has been shown on a differently washed glass surface. Reference is made to the theoretical and experimental works following the early wor...

Universal amplitude ratios of surface tensions near a critical point in a liquid binary system: Water‐2,5 lutidine

Experimental data of surface tensions along the critical isochore (1) and the two branches of the coexistence curve (2,3) for the water‐2,5 lutidine system have been used in order to check signs and values of the universal amplitude ratios of the critical laws in the forms σα,j=σc+A(T−Tc)+Bj(T−Tc)μ, j=1,2,3, with imposed μ=1.26. A and the Bj’s being highly correlated, several statistical tests using the values of the ratios have been used. Experimental values are compatible with P+=B/Bi=−0.59 (B: isochore; Bi: interfacial tension in the two phases system), maybe with Q=B/B‘=−0.83 (B‘ one branch of the coexistence curve) and certainly with its sign. The other ratios cannot be verified at all by the experimental data.

Activities and thermodynamic excess properties of aqueous 2,5-dimethylpyridine mixtures near the critical demixing point : comparison with 2,6-dimethylpyridine-water mixtures

Activities of 2,5-dimethylpyridine in aqueous solution have been measured at eleven temperatures, two below and nine above the lower critical temperature of the mixture, by the dynamic method of Randall and Weber. Gibbs free energy, enthalpy and entropy are derived to obtain excess quantities and all the results are discussed in connection with the liquid-liquid phase separation, the critical situation and the association properties of the molecules. A comparison is also made with the aqueous 2,6-dimethylpyridine system. A new version of the phase diagram is proposed.

Ellipsometry and adsorption: The determination of isotherms and the adsorbed layer thickness and fluctuations of the composition in the liquid-vapor interface

Abstract In the first part of this paper the mole fraction (x2σ) and the activity ( a 2σ) of an adsorbed molecule 2 in the surface phase (phase σ) of a binary liquid-vapor system have been obtained by linking Drudes part of the ellipticity coefficient, ϱ , and the relative surface excess Γ21. In the second part the equations giving the composition fluctuations and the surface tension fluctuations in the surface phase considered to be an autonomous phase have been theoretically established. The fluctuations are expressed with respect to surface phase variables evaluated in the first section.

On the flexibility and the dynamics of DNA.

We describe and discuss the stability conditions of a naked double stranded DNA molecule starting from the evaluation of condensation or compactness fluctuation of this molecule embedded in pure water.