Quartz electrophoretic cell

The parabola method makes it possible to measure the potential of cell walls. Usually, the cell is made of quartz, and the parabola method thus offers the possibility of determining the lEP of one material that has already been extensively studied. The potentials of macroscopic specimens of other materials can also be determined from the mobility profile [273-275] by replacement of the original cell wall of a commercial electrophoretic cell by a flat specimen of the material of interest. For example, in [276], the lEP of a basal plane of mica found from the mobility profile was different from the lEP of a mica dispersion. Only a few types of electrophoretic devices (most of which are no longer available on the market) can be used to determine potentials by means of electro-osmosis. 

Electrophoretic mobilities of the quartz particles in cobalt (II) perchlorate solutions were determined with a calibrated Zeta-Meter apparatus. Coagulation sedimentation behavior was followed using a stop-flow type apparatus. The dispersion is pumped in a closed loop from an equilibration vessel through an optical cell located in the sample compartment of a recording spectrophotometer. From the optical densitytime curve obtained from the time the pump is switched off, the turbidity index (in arbitrary units) is obtained as the slope of the curve at zero time. 

Instrumentation. A Rank Bros, micro-electrophoresis unit was used in those studies, with a specially made quartz cell having a 6 cm. path length of rectangular inside cross-section (l mm thick, 10 mm deep) in which the Komagata equation (25) predicts zero mobility of the liquid phase in planes located at 0.612 of the distance b from the center plane of the cell to the wall. In electrophoresis experiments 300 to 1200 volts were applied to the cell and mobilities measured in planes a distance h from the center plane. The results were graphed as observed velocity versus (h/b)z as proposed by van Gils (26J, and if the straight lines characteristic of perfect parabolic flow resulted, the electrophoretic mobilities (v ) observed at h/b=0.612 were considered acceptable for calculation of zeta-potential. Zeta-potentials were calculated by the Huckel equation (27) ... 

Electrophoretic Mobilities. The electrophoretic mobilities reported in Figures 4 and 6 were measured using a Rank Brother apparatus Mark II and flat quartz cell at 25 C. At least 20 particles were timed at both stationary layers. The error is within 5 to 10%. 

Various planar membrane models have been developed, either for fundamental studies or for translational applications monolayers at the air-water interface, freestanding films in solution, solid supported membranes, and membranes on a porous solid support. Planar biomimetic membranes based on amphiphilic block copolymers are important artificial systems often used to mimic natural membranes. Their advantages, compared to artificial lipid membranes, are their improved stability and the possibility of chemically tailoring their structures. The simplest model of such a planar membrane is a monolayer at the air-water interface, formed when amphiphilic molecules are spread on water. As cell membrane models, it is more common to use free-standing membranes in which both sides of the membrane are accessible to water or buffer, and thus a bilayer is formed. The disadvantage of these two membrane models is the lack of stability, which can be overcome by the development of a solid supported membrane model. Characterization of such planar membranes can be challenging and several techniques, such as AFM, quartz crystal microbalance (QCM), infrared (IR) spectroscopy, confocal laser scan microscopy (CLSM), electrophoretic mobility, surface plasmon resonance (SPR), contact angle, ellipsometry, electrochemical impedance spectroscopy (EIS), patch clamp, or X-ray electron spectroscopy (XPS) have been used to characterize their... 

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