Electroosmotic properties

With the aim of developing microchip CE systems from materials that have properties similar to those of glass but are easier and less expensive to fabricate, a ceramic material, aluminium borosilicate, has been employed [8]. Although electroosmotic properties are similar to those of fused silica and fabrication can be accomplished using either milling or laser ablation, its use has not been widespread. 

Chein, R.-L. and Helmet, J. C., Electroosmotic properties and peak broadening in field-amplified capillary electrophoresis, AnoZ. Chem., 63,1354, 1990. 

Capillary wall Generally, the most straightforward approach is to use an uncoated fused silica capillary. But sometimes this is not possible because of adsorption problems to the capillary wall, or other wall properties are needed to control the electroosmotic flow. In literature, there are multiple examples. Besides permanently coated capillaries, there are several descriptions of dynamic coatings available, e.g., triethanolamine, Triton X-100, Polybrene, and quaternary ammonium salts. The advantage of these dynamic coatings is that the coating can be renewed between injections, which could improve repeatability and reproducibility of the separation. 

Dittmann, M. M., and Rozing, G. P. (1997). Capillary electrochromatography investigation of the influence of mobile phase and stationary phase properties on electroosmotic velocity, retention, and selectivity. J. Microcolumn Sep. 9, 399-408. 

One of the most widely used forms of gel electrophoresis is known as sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Polyacrylamide gel has several advantages that account for its extensive use. It has minimal adsorptive properties and produces a negligible electroosmotic effect (Hjelmeland and Chrambach 1981). In identity tests, for the determination of molecular weight, SDS-PAGE has been shown to be an appropriate, fast, and easy method that is often used in quality control laboratories. The use of SDS-PAGE followed by a densitometric analysis, such as MS, is a helpful technique for the determination of peptide or... 

The development of the first transdermal patches in the 1980s generated considerable interest in this route of drug administration. Soon afterwards, iontophoresis was rediscovered and its potential to contribute to the new field of transdermal drug delivery was examined. This work provided the basic principles for modern iontophoretic devices [13,18-21]. Furthermore, and importantly, they demonstrated the existence of a (primarily) electroosmotic, convective solvent flux during transdermal iontophoresis [10,11,22-24], and it was shown that the permselective properties of the skin (a) could be exploited to enhance the transport of neutral, polar species and (b) have a clear impact on ionic transport. Subsequent research has better characterized skin permselectivity and the factors which determine the magnitude of electroosmosis [25-27],... 

As in the case of normal chromatography both stationary and mobile phases are also required in NLC. On the other hand, in NCE hydrophilic channel walls with improved control over electroosmotic flow are required for better separation of biological samples. Briefly, the separation efficiencies and selec-tivities in NLC and NCE depend on the properties of the microchannels, and, therefore, surface modification of the microchannel is usually necessary to achieve good separation of a variety of analytes. Recently, Muck and Svatos... 

P 67] Simulations were made following experiments made previously [156], Therein 0.11 mM Rhodamine B solutions in 20 mM carbonate buffer were mixed with the same carbonate buffer. For the buffer solution, the physical properties of water were approximated. For Rhodamine B, a diffusion coefficient of 2.8 10-6 cm2 s-1 was taken. Electroosmotic flow was applied for liquid transport. For all of the walls in the domain the electroosmotic (EO) mobility was set to 3.4 10-4 cm2 V-1 s 1, which corresponds to a zeta potential (Q of-44.1 mV. The electric field in the outlet channel was 1160 V cm-1. The Reynolds number was 0.22. The electric field strength was set low in order to decrease diffusive (pre-)mixing prior to the groove structure. 

The electrophoretic mobility of a solute is a characteristic property of the solute that describes its movement under the influence of an applied field. Electrophoretic mobility is dependent both on the charge density of the solute and on physical properties of the buffer system. The apparent mobility of a species, that is, the mobility that the species appears to possess, is the sum of the electrophoretic mobility and the mobility of the electroosmotic flow. 

The velocity of the electroosmotic flow can be affected by altering the properties of the buffer system or by changing the applied voltage. The factors involved are... 

In order to evaluate the steady-state water profile in the membrane of a PEFC under given operating conditions, the necessary membrane transport properties required thus include water uptake by the membrane as function of water activity and membrane pretreatment conditions, A(aw) (covered in Section 5.3.1) the diffusion coefficient of water in the membrane as a function of membrane water content, D ) the electroosmotic drag coefficient as a function of membrane water content, (A) and the membrane hydraulic permeability, A hy(i(A). Section 5.3.2 includes a discussion of water transport modes in ionomeric membranes. 

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