Streaming potential, instruments

U is the streaming potential, p is the pressure, eT and sp are the dielectric constant and the electric constant, respectively. rj is the viscosity and k is the conductivity of the solution. Since the instrument requires a minimum conductivity of the solution, measurements were done in a background electrolyte (KC1) concentration of 10-5 to 10-3 M. 

The potential of macroscopic grains can be conveniently measured by electroosmosis, A few commercial instruments are available, and many home made designs have been described in literature [52], The apparatus described in Ref. [53] requires samples in form of two flat disks about 50 mm in diameter one of which has a central hole 6 ram in diameter to measure radial flow streaming potential. 

An introduction to electrokinetic phenomena can be found in [240] and in handbooks of colloid chemistry. The choice of method and instrument suitable for the character of a sample is key to successful electrokinetic measurements. In principle, all techniques and all instruments should produce the same potential and the same IEP in a system of interest. A few multi-instrument studies have been published. For example, [241] reports lEPs obtained by streaming potential and by electrophoresis (using a commercial apparatus). A multi-instrument electrokinetic study of alumina in O.OIM NitNO, is reported in [242]. The IEP was also relatively consistent with different solid-to-liquid ratios. Glass capillaries with inner sides coated with spherical nanosize hematite particles showed an IEP at pH = 5, while the IEP of the original hematite obtained by electrophoresis was at pH 9.3 [243]. 

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... 

The tables in Chapter 3 report results obtained using the following commercial instruments based on streaming potential ... 

Description Electrolyte T Method Instrument pH, Reference Original 0-0.01 M KCl iep Streaming potential 5.8 [2232,2239]... 

Streaming potential was measured using a Brookhaven Instruments Corp. (Holtsville, NY, USA) BI-EKA commercial instrument which has a crossflow slit geometry. Childress and Elimelech (1996) and Elimelech et al. (1994) described the measuring cell and the principle in detail. For comparison, another surface potential analyser was used as constructed and described by Pihlajamaki (1998). The streaming potential, from which the zeta potential can be calculated with the Helmholtz-Smoluchowski equation, was measured in the presence of 10 mM NaCl, 1 mM NaHCO s and 0.5 mM CaCh, unless otherwise... 

Streaming potential measurements have been used extensively to eharaeterize surfaee properties of fibers (25), and this technique has been applied to analyze the effects of shampoos and conditioners on hair by a number of authors (26-28). Jachowicz and his coworkers developed new instrumentation for this purpose, which permits the simultaneous determination of electrokinetic and permeability parameters on hair fiber plugs. DEPA is... 

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. 

The largest application segment for filter photometers is in the area of combustion gases analysis, primarily for CO, CO2, hydrocarbons, SO2, etc. Other major areas of application include the petrochemical industry, with natural gas and other hydrocarbon process gas streams being important applications. As measurements become more complex, there is the need for more advanced instrumentation. Variable or tunable filter solutions (as described above) or full-spectrum FTIR or NIR instruments are normally considered for these applications, primarily in terms of overall versatility. Now that array-based systems are becoming available, there is a potential for an intermediate, less expensive, and more compact solution. Note that compact instrumentation tends to be environmentally more stable, and is well suited for industrial applications. 

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