Effect Of Electroosmosis Research Articles

Effect of electroosmosis on detection in isotachophoresis

The effect of electroosmosis on the relative sharpness of the zone boundaries and hence the detection limit in isotachophoresis is discussed. A high concentration and a low pH of the leading electrolyte were found to be favourable. The magnitude and sign of the ζ-potential of the capillary wall was measured by streaming potential determinations as a function of concentration, pH and additives. Poly(vinyl alcohol), hydroxyethylcellulose and hydroxypropylmethylcellulose decrease the ζ-potential sufficiently, whereas cationic detergents reverse its sign and thus the direction of the electroosmotic flow. Both were found to be favourable in anionic separation. Fused-silica capillaries and the effect of methanol were also investigated.

High-resolution separations based on electrophoresis and electroosmosis

The related electrokinetic effects of electrophoresis and electroosmosis may be used to achieve high resolution separations. An “instrumental” version of zone electrophoresis carried out in 75 μm I.D. glass capillaries is described. This technique demonstrates excellent resolution of charged substances in a short time. Using virtually the same apparatus, reversed-phase chromatography is performed with electroosmotic pumping of an acetonitrile mobile phase. This technique also produces separations with excellent efficiency. Very low values of reduced plate height are found, which suggests that column packing irregularities are less important when electroosmotic flow is used instead of flow generated by pressure.

Protein concentration and recovery from gel slabs by displacement electrophoresis (isotachophoresis) and the effects of electroosmosis and counter flow

AbstractAlternative technical solutions of the concentration of protein samples or the recovery of proteins from gel slabs by displacement electrophoresis are demonstrated. The samples are collected at a boundary between high‐mobility leading ion and a low‐mobility terminating ion either in a small Sephadex G‐25 columns or in free solution in a rotating‐tube free electrophoresis apparatus. The boundary is kept stationary during electrophoresis by a counter flow of leading solution. Spacers and colored markers can be used to facilitate the collection of the proteins. Investigations showed that electroomosis is a very local phenomenon and that, as expected, the magnitude of the effects depends on the conductivity (field strength) of the solution. This implies that electroomosis will vary among different zones in a discontinuous system (as in displacement electrophoresis). Therefore, in most experiments om free solution it is very advantageous to arrange the system such that electrophoresis does not occur.

Ionic fluid stress effect on electroosmosis in electrophoresis

The electroosmosis effect in electrophoresis experiments has been investigated theoretically using multi-component fluid dynamics. The ionic fluid shearing stress effects and correct boundary conditions have been taken into consideration in order to obtain the solutions of the component fluid velocity profiles. Several model problems with different situations and boundary conditions are considered.

Effects of unstirred layers or transport number discontinuities on the transient and steady-state current-voltage relationships of membranes

The effects of current-induced electrolyte accumulation and depletion on the electrical properties of a two-layered membrane system have been examined. The membrane consisted of a charged, ion permselective layer and an uncharged, non-selective layer. The model was designed to reveal the properties of membranes possessing long pores with ionic charges at one end or of ion-selective membranes bounded by highly unstirred aqueous layers. Electrolyte concentration profiles in the inert layer and their time-dependent changes were obtained from solutions of the diffusion equation under the condition of constant current. The profiles were then used to calculate the voltage developed across the membrane at various times after the current is switched on. The theoretical results are presented in the form of i-V curves with reduced coordinates that can be used to obtain time-current-voltage relationships for membranes of the type considered having any thickness of the non-selective layer and bathed in any concentration of any 1:1 electrolyte. Experimental results on a model composite membrane were in good agreement with calculations that assume that ion transport occurs only under the influence of electrical potential and concentration gradients, suggesting that in such systems, the combined effects of convection, osmosis, electro-osmosis, and concentration-dependence of diffusion coefficients, activity coefficients, and transference numbers are small. Voltage fluctuations in the form of periodic spikes were observed experimentally at the limiting current density (the current density at which the electrolyte concentration at one surface of the selective layer goes to 0). These phenomena were not seen when the current was in the direction leading to accumulation of electrolyte in the non-selective (unstirred) layer. Such composite membranes can exhibit S-shaped and N-shaped i-V curves under ramp-voltage and ramp-current clamps, respectively.

Electroosmotic Reduction of Ocean Bottom Breakout Forces and Times

Laboratory model pullout tests were conducted with a cylindrical object, 1 sediment, 1 object in situ time, 3 electrode configurations, and electric potential gradients of 0, 0.25, and 0.5 V/cm to determine the effect of electroosmosis on reducing force and time requirements for breaking objects free of soft sediments.Results show electroosmosis to be very effective in reducing breakout times. The relationship between the breakout force ratio and breakout time can be expressed in terms of 2 empirical parameters. Electrical power requirements to achieve breakout appear to be independent of electrode configurations but do depend on electric potential gradients.

Theory of the electroosmosis effect in the electrophoresis

Theory of the electroosmosis effect in the electrophoresis

The Teorell membrane oscillator as a mechano-electric transducer

The results of a recent quantitative analysis of the Teorell membrane oscillator are utilized to explore its role as an excitability analogue. Special attention is paid to its role as a mechano-electric transducer. A membrane of exceptionally well-defined pore structure has been used in this study. The analogue properties arise from nonlinear coupling between water and salt fluxes. When the membrane is simultaneously subjected to controlled gradients of hydrostatic pressure, electrical potential and concentration, bi-stable stationary states can be produced. These arise from the opposing effects of pressure and electro-osmosis on the volume flow. Transitions between these states show hysteresis. The factors governing such transitions are analogous to certain types of stimuli encountered in the natural excitation process. The membrane system also shows oscillatory behavior when the hydrostatic pressure gradient is allowed to vary under constant current conditions. This property is related to the bi-stable stationary state phenomena and is compared to the regenerative behavior found in biologically excitable tissues. Particular emphasis is placed upon analogies between the membrane oscillator and certain natural tissues. The importance of the nonlinear nature of the force-flux coupling in the analogue is stressed, and its possible relevance to biological excitability indicated. Some consideration is also given to the role of electro-osmotic flux coupling in biological tissues.

Isoelectric focusing in layers of granulated gels: I. Thin-layer isoelectric focusing of proteins

Anticonvective stabilization of the pH gradient in isoelectric focusing by layers of granulated gels is described. Analytical separations of an artificial mixture of proteins by thin-layer isoelectric focusing have been compared with those obtained by the density gradient technique. Detection of proteins by staining with different dyes and some implications due to the presence of carrier ampholytes are commented. The effect of isoelectric precipitation, electroosmosis and concentration of carrier ampholytes on thin-layer isoelectric focusing has been studied and the load capacity of layers of granulated gels has been determined. The principle of localized spreading with mixtures of the pH 3–10 and narrow pH range carrier ampholytes is described. Different granulated gels of the Sephadex and Bio-Gel series have been compared. In experiments with gels of varying fractionation ranges, gel porosity did not affect the isoelectric points of selected pH marker proteins. Constant isoelectric points of pH marker proteins have been determined under strongly varying experimental conditions of time, voltage and site of application. The potential of the method for different fields of application is illustrated by focusing of serum proteins (α-globulins), enzymes (ribonuclease and deoxyribonuclease) and a snake venom.

Forced-flow electrophoretic filtration of clay suspensions: Filtration in an electric field

Separation of suspended bentonite particles has been studied by forced-flow electrophoresis. Essentially, it entails filtration of clay through a membrane filter in a d.-c. electric field. The experimental data have been found to obey the established Sperry or Carman filtration equation, provided it is modified to account for the effect of electroosmosis through the filter medium and the filter cake. In addition, the electric field of proper polarity causes electrophoretic removal of clay particles from the filtering surface. As a result, for any given rate of filtration there is a critical voltage at/or above which all filter cake build-up is prevented and the filtration rate through the cell remains essentially constant. Electrophoretic filtration of colloids is most efficient at this critical voltage.

Electro-Osmosis in Soils

Summary The present paper shows that, from a practical point of view, the electro-osmotic transport of water may be assumed to be constant for all soils. The magnitude of the osmotic permeability was found to be ke=5 × 10−5 cm. per sec. for for 1 volt per cm. By comparing ke, with the hydraulic permeability the heights to which the water can be shifted by electro-osmosis were computed and also measured by laboratory tests. For this purpose a special apparatus was constructed. The fact that with colloidal materials agreement between theoretical equilibrium heads and test results exist only for the short interval of time immediately after applying an electric potential was attributed to the development of cracks within the mass of material. The possibility of diverting the flow of pore-water away from cuttings is discussed and illustrated by practical examples. Some indications are given of the magnitude of the required consumption of energy for a few arrangements of electrodes. An explanation is also offered for the favourable effect of electro-osmosis on the consolidation of soft soil deposits.