Electrokinetic characterization

Numerous other applications could be listed in which electrokinetic characterization provides a convenient experimental way of judging the relative stability of a system to coagulation. Paints, printing inks, drilling muds, and soils are examples of additional systems with properties that are extensively studied and controlled by means of the f potential. 

It can be summarized that ellipsometric measurements proved the formation of a surfactant adsorption layer on the photoresist surface. At ceg- it is assumed to form a monolayer. To get more information about the adsorption layer and its influence on the surface properties of the photoresist, an electrokinetic characterization of unexposed and processed photoresist in solutions of the cationic surfactant was carried out. The zeta potential of the photoresist layers is given in Fig. 8 as a function of the surfactant concentration. The measurement was performed at pH = 6 in a background electrolyte (KC1) concentration of 10-5 M to ensure the minimum conductivity of the solution necessary for the measurement. 

FIG. 4 The rectangular electrophoresis chamber for electrokinetic characterization of macroscopic surfaces. 

This section will focus mainly on characterization of the physical nature of the dispersed phase or its size distribution. Electrokinetic characterization techniques, which determine the electric double-layer properties of the dispersed phase, will be only briefly mentioned. Again, electrokinetic properties, their significance, and their measurement have been covered in review articles 44, 45). 

Fa, K. et al.. The significance of electrokinetic characterization for inteipreting interfacial phenomena at planar, macroscopic interfaces, Phys. Chem. Chem. Phys., 7, 678, 2005. 

Szymezyk. A. et al.. Electrokinetic characterization of mixed alumina-titania-siUca MF membranes by stt eaming potential measurements. Desalination. 115, 129, 1998. 

Lehmann, C., Mockel, D., and Staude, E., Permeation and tangential flow streaming potential measurements for electrokinetic characterization of hack-etched microfil-hation membranes, J. Membr. Sci., 159, 243, 1999. 

J.-F. Wang, R. E. Riman, and D. J. Shanefield, "Reliable Electrokinetic Characterization Procedures for Ceramic Powders," Presented at Materials Research Society Meeting, San Francisco. Calif., April 16, 1990. 

Ariza, MJ Rodriquez-Castellon, E Munoz, M Benavente, J. Surface chemical and electrokinetic characterizations of membranes containing different carriers by X-ray photoelectron spectroscopy and streaming potential measurements study of the effect of pH. Surface and Interface Analysis, 2002, 34, 637-641. 

Peula, J.M., Puig, J., Serra, J., de las Nieves, R.J., and Hidalgo-Alvarez, R. 1994. Electrokinetic characterization and colloidal stability of polystyrene latex particles partially covered by IgG/a-CRP and m-BSA proteins. Colloids Surf. A 92 127-36. 

Peula, J.M., Hidalgo-Alvarez, R., and de las Nieves, F.J. 1998. Covalent binding of proteins to acetal-functionalized latexes. I. Physics and chemical adsoption and electrokinetic characterization. J. Colloid Interface Sci. 201 132-8. 

Rands C, Webb BW, Maynes D (2006) Characterization of transition to turbulence in microchannels. Int J Heat Mass Transfer 49 2924-2930 Ren L, Qu W, Li D (2001) Interfacial electrokinetic effects on liquid flow in micro-channels. Int J Heat Mass Transfer 44 3125-3134... 

As the particle moves relative to the electrolyte solution, the layer of water mol-ecnles that is directly adjacent to the particle surface is strongly bonnd and will be pnlled along. The thickness of this bonnd layer is approximately one or two diameters of a water molecule. We shall write x, for the x-coordinate of this layer s outer boundary, which is the slip plane. The electrostatic potential at this plane relative to the potential in the bulk solution is designated by the Greek letter and called the zeta potential or electrokinetic potential of the interface discussed. This potential is a very important parameter characterizing the electrokinetic processes in this system. 

The charges present on the insulator surface in contact with the solution give rise to an accumulation of ions of opposite sign in the solution layer next to the surface, and thus formation of an electric double layer. Since straightforward electrochemical measurements are not possible at insulator surfaces, the only way in which this EDL can be characterized quantitatively is by measuring the values of the zeta potential in electrokinetic experiments (see Section 31.2). 

Trone, M. D., Khaledi, M. G. Statistical evaluation of linear solvation energy relationship models used to characterize chemical selectivity in micellar electrokinetic chromatography. J. Chromatogr. A 2000, 886, 245-257. 

Lee et al. [30] described a micellar electrokinetic capillary chromatographic method for the determination of some antiepileptics including valproic acid. They used a fused silica capillary column (72 cm x 50 pm) and SDS as the micellar phase and multiwavelength UV detection. Reaction conditions, such as pH and concentration of running buffer were optimized. Solutes were identified by characterizing the sample peak in terms of retention time and absorption spectra. Recoveries were 93-105%. 

Fang X, Yang L, Wang W, et al. Comparison of electrokinetics-based multidimensional separations coupled with electrospray ionization-tandem mass spectrometry for characterization of human salivary proteins. Anal. Chem. 2007 79 5785-5792. 

Besides CZE and NACE, micellar electrokinetic chromatography (MEKC) is also widely used, and ionic micelles are used as a pseudo-stationary phase. MEKC can therefore separate both ionic and neutral species (see Chapter 2). Hyphenating MEKC with ESI/MS is problematic due to the non-volatility of micelles, which contaminate the ionization source and the MS detector, resulting in increased baseline noise and reduced sensitivity. However, MEKC—ESI/MS was applied by Mol et al. for identifying drug impurities in galantamine samples. Despite the presence of non-volatile SDS, all impurities were detected with submicrogram per milliliter sensitivity and could be further characterized by MS/MS. 

The importance of materials characterization in fuel cell modeling cannot be overemphasized, as model predictions can be only as accurate as their material property input. In general, the material and transport properties for a fuel cell model can be organized in five groups (1) transport properties of electrolytes, (2) electrokinetic data for catalyst layers or electrodes, (3) properties of diffusion layers or substrates, (4) properties of bipolar plates, and (5) thermodynamic and transport properties of chemical reactants and products. 

PG Muijselaar, HA Claessens, CA Cramers. Characterization of pseudostation-ary phases in micellar electrokinetic chromatography by applying linear solvation-energy relationships and retention indexes. Anal. Chem. 69 1184—1191... 

MA Schwarz, RH Neubert, G Dongowski. Characterization of interactions between bile salts and drugs by micellar electrokinetic capillary chromatography. Part I. Pharm Res 13 1174-1180, 1996. 

Microemulsion electrokinetic chromatography was introduced to study the affinity of various cephalosporins [cefpim, cefpirom, cefaloridin, cefaclor, cephalexin, cefuroxim, cefotaxim] in microemulsions and micellar (MC) systems. The affinity of various cephalosporins in microemulsions was characterized calculating the capacity factor. The capacity factor values of the cephalosporins in micellar systems and in microemulsions are given in Table... 

Mrestani, Y., El-Mokdad, N., Riittinger, H., Neubert, R. (1998). Characterization of partitioning behavior of cephalosporins using microemulsion and micellar electrokinetic chromatography. Electrophoresis 19 2895—2899. 

Schnee, V. R, Baker, G. A., Rank, E., and Ralmer, C. R, Electrokinetic chromatographic characterization of novel pseudo-phases based on N-alkyl-N-methyl-pyrrolidinium ionic liquid type surfactants. Electrophoresis, 2J, 4141-4148,2006. 

Region 2 is characterized by a marked change in the slope of the adsorption isotherms. This results from the onset of association of the hydrocarbon chains of the surfactant ions adsorbed in the Stem plane. The mean separation distance of adsorbed ions under these conditions is about 70 A., which approximates the mean separation distance in bulk at the c.m.c. In such adsorption phenomena, there is a relationship between this asociation and the formation of micelles in bulk solution. For example, electrokinetic studies (1) on quartz at neutral pH showed that alkylammonium ions associate in the Stem plane when their bulk concentration is approximately one hundredth of the c.m.c. This association which has been called hemimicelle formation (3), gives rise to a specific adsorption potential which causes the adsorption to increase markedly and brings about a reversal in the sign of the potential at the Stem plane. The hemimicelle concentration, that is the bulk concentration necessary... 

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