Kinematic and volumetric analysis of coupled transmembrane fluxes of binary electrolyte solution components.

The paper deals with relationships between the individual transmembrane fluxes of binary electrolyte solution components and the experimentally measurable quantities describing rates of transfer processes, namely, the electric current, the transmembrane volume flow and the rates of concentration changes in the solutions adjacent to the membrane. Also, we collected and rigorously defined the kinetic coefficients describing the membrane selective and electrokinetic properties. A set of useful relationships between these coefficients is derived. An important specificity of the proposed analysis is that it does not use the Irreversible Thermodynamic approach by analyzing no thermodynamic forces that generate the fluxes under consideration. Instead, all the regularities are derived on the basis of conservation and linearity reasons. The terminology "Kinematics of Fluxes" is proposed for such an analysis on the basis of the analogy with Mechanics where Kinematics deals with regularities of motion by considering no mechanic forces. The only thermodynamic steps of the analysis relate to the discussion on the partial molar volumes of electrolyte and ions that are the equilibrium thermodynamic parameters of the adjacent solutions. These parameters are important for interrelating the transmembrane fluxes of the solution components and the transmembrane volume flow. The paper contains short literature reviews concerned with the partial molar volumes of electrolyte and ions: the methods of measurement, the obtained results and their theoretical interpretations. It is concluded from the reviews that the classical theories should be corrected to make them applicable for sufficiently concentrated solutions, 1 M or higher. The proposed correction is taken into account in the kinematic analysis.

A Multistate Adsorption Model for the Characterization of C13DMPO Adsorption Layers at the Aqueous Solution/Air Interface.

Experimental data for tridecyl dimethyl phosphine oxide (C13DMPO) adsorption layers at the water/air interface, including equilibrium surface tension and surface dilational viscoelasticity, are measured by bubble and drop profile analysis tensiometry at different solution concentrations and surface area oscillation frequencies. The results are used to assess the applicability of a multistate model with more than two possible adsorption states. For the experiments with single drops, the depletion of surfactant molecules due to adsorption at the drop surface is taken into account. For the assessment, the same set of model parameters is used for the description of all obtained experimental dependencies. The agreement between the proposed model and the experimental data shows that for the nonionic surfactant C13DMPO, the description of the adsorption layer behavior by three adsorption states is superior to that with only two adsorption states.

Dilational Viscoelasticity of Proteins Solutions in Dynamic Conditions.

Drop profile analysis tensiometry used in the oscillating drop mode provides the dilational viscoelasticity of adsorption layers at liquid interfaces. Applied during the progress of adsorption the dynamic surface rheology can be monitored. For ß-casein solutions at the same surface pressure values, the larger the dynamic dilational viscoelasticity the longer the adsorption time, i.e., the smaller the studied protein concentration is. For ß-lactoglobulin and human serum albumin, the differences in the viscoelasticity values are less or not dependent on the adsorption time at identical surface pressures. The observed effects are caused by the flexibility of BCS, while the globular proteins BLG and HSA do not change their conformation significantly within the adsorption layer.