Streaming current measurement

A similar IEP value for untreated wool (3.6) was recently obtained by Jocic et al. [32], using EKA streaming current measurements. 

When the solid phase is fixed (e.g., as a capillary, membrane, or porous plug), a forced flow of liquid induces an electric field. The potential difference is sensed by two identical electrodes. The streaming potential or streaming current can be used to determine the potential. The streaming potential and electro-osmosis can be observed in similar experimental setups, except that the natures of the force and the flux are reversed. Thus, the recommendations and limitations discussed in Section 2.1.2 also apply to measurements based on the streaming potential. For example, the instrument cell induces a streaming potential, which may contribute substantially to the result of the measurement. A linear dependence between the potential obtained by electrophoresis and the streaming current measured by a commercial apparatus was observed in... 

Roessler, S. et al.. Characterization of oxide layers on Ti6A14V and titanium by streaming potential and streaming current measurements, Colloids Surf. B, 26, 387, 2002. 

Here, L denotes the length of the capillary. An important advantage of the streaming current measurement is that the surface conductivity does not matter for the calculation (see Equation 5.364), and experimental determination of is not necessary. Similar experiments were performed by Scales et al. to determine the potential of mica surface. 

Adsorption of Al(13)-Keggin clusters to sapphire c-plane single crystals Kinetic observations by streaming current measurements, Appl. Surf. Sci. Vol. 256, 5406-5411, 0169-4332. 

It goes without saying that surface conduction does not play a role in streaming current measurements because these are performed in the absence of an electric field. 

Rindlav-Westling A, Stading M, Gatenholm P (1998) Structure, barrier and mechanical properties of amylose and amylopectin films. Carbohydr Polym 36 217-224 Roessler S, Zimmermann R, Schamweber D, Werner C, Worch H (2002) Characterization of oxide layers on T16A14V and titanium by streaming potential and streaming current measurements. Colloid Surf B 26 387-395... 

Duval, J. F. L., Zimmermann, R., Cordeiro, A. L., Rein, N., Wemer, C. (2009). Electrokinetics of diffuse soft interfaces. IV. Analysis of streaming current measurements at thermore-sponsive thin films. Langmuir, 25, 10691-10703. 

Figure 5 shows the time evolution of representative streaming current measurements in the cellular convection and turbulent flow regimes. The periodic variations at lower speeds has period corresponding to the frequency f = U/X where X 2nd/3.12 is the spacing of flow cells at the onset of instability where d = 2" 1 annulus gap and U is the... 

Schweiss R, Welzel PB, Werner C, KnoU W. (2001) Dissociation ofsurfiice functional groups and preferential adsorption of ions on self-assembled monolayers assessed by streaming potential and streaming current measurements. Langmuir 17 4304-4311. 

The presence of surface conductance behind the slip plane alters the relationships between the various electrokinetic phenomena [83, 84] further complications arise in solvent mixtures [85]. Surface conductance can have a profound effect on the streaming current and electrophoretic mobility of polymer latices [86, 87]. In order to obtain an accurate interpretation of the electrostatic properties of a suspension, one must perform more than one type of electrokinetic experiment. One novel approach is to measure electrophoretic mobility and dielectric spectroscopy in a single instrument [88]. 

Automated controls for flocciJating reagents can use a feedforward mode based on feed turbidity and feed volumetric rate, or a feed-back mode incorporating a streaming current detector on the flocculated feed. Attempts to control coagulant addition on the basis of overflow turbidity generally have been less successful. Control for pH has been accomplished by feed-forward modes on the feed pH and by feed-back modes on the basis of clarifier feedwell or external reaction tank pH. Control loops based on measurement of feedwell pH are useful for control in apphcations in which flocculated sohds are internaUy recirculated within the clarifier feedwell. 

Streaming Current Detectors These units produce a measurement closely related to the zeta potential of a suspension and are used successfully in optimizing the coagulant dose in clarification applications. 

Several devices are available commercially to measure mobihty. One of these (Zeta-Meter Inc., New York) allows direct microscopic measurement of individual particles. Another allows measurement in more concentrated suspensions (Numinco Instrument Corp., Monroeville, Pa.). The state of the charge can also be measured by a streaming-current detecdor (Waters Associates, Inc., Framingham, Mass.). For macromolecules, more elaborate devices such as the Tisehus moving-boundaiy apparatus are used. 

The limiting-current method has been used widely for studies in packed and fluidized beds (see Table VII, Part H). Limiting current measurements in these systems overlap in part with the design and analysis of packed-bed and fluidized-bed electrochemical reactors in particular the potential distribution in, and the effectiveness of, such reactors (for example, for metal removal from waste streams) is an extensive area of research, which cannot be covered in this review. For a complete discussion of porous flow-through electrodes the reader is referred to Newman and Tiedemann (N8d). 

An ELSD converts the HPLC eluent into a particle stream and measures the scattered radiation. It offers universal detection for nonvolatile or semivolatile compounds and has higher sensitivity than the RI detector (in the low ng range) in addition to being compatible with gradient analysis. ELSD is routinely used in combinatorial screening. Response factors are less variable than that of other detectors. An ELSD consists of a nebulizer equipped with a constant temperature drift tube where a counter-current of heated air or nitrogen reduces the HPLC eluent into a fine stream of analyte particles. A laser or a polychromatic beam intersects the particle stream, and the scattered radiation is amplified by a photomultiplier. Manufacturers include Alltech, Polymer Laboratories, Shimadzu, Waters, Sedere, and ESA. 

In 1980 Bemhardsson et introduced an automated electrochemical method for CPT determination. The specimen is mounted as described in Section IV.2 (ii) using a stream of argon to avoid crevice corrosion and 0.02-5% sodium chloride as electrolyte. The CPT is determined by a potentiostatic test method using an instrument called the Santron CDT 400 for potential control, temperature control, and current measurements. 

There are actually no experimental measurements of protonic streaming currents (Lu) and coupled water and methanol transport (L23 = L32) however, the first may be related to the hydrodynamic component of the electro-osmotic drag L /Ln, Lis/Lu) (see discussion in Section 3.2.1.1). The second is expected to be qualitatively related to the ratio of the electro-osmotic drag coefficient of water and methanol (L12/Z.13). In the following, the directly accessible transport coefficients o (Do), FH2O, MvieOH,... 

A potential is built up, which tends to counteract the flow of the counter ions and accelerates the flow of the co-ions, in such a manner that the solution streaming out is electro-neutral. The potential can be measured in the usual way by placing two reference electrodes in the solutions on either side of the membrane. If these electrodes are short-circuited, an electrical current flows through the connecting wire. This current is called the streaming current. 

The streaming current can be measured if the high- resistance voltmeter is replaced with a microammeter of low resistance compared with that of the plug. An alternating streaming current can... 

In this paper we investigate the process of alternate adsorption of cationic polyelectrolyte and anionic surfactant, structure and properties of adsorbed layers depending on different factors (molecular weight of PE, concentration of polyelectrolyte and surfactant, adsorbed layer formation time, the flow rate of the solution) by measuring potential and streaming current using the capillary electrokinetic method. 

Streaming currents can in principle be measured by placing two identical reversible electrodes at the ends of the capillaries and connecting them by a low-resistance external lead, see sec. 4.4. 

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