Capillary zone electrophoresis electrophoretic mobility

Capillary zone electrophoresis, an up-to-date high resolution separation method useful for proteins and peptides, has been shown to be a useful method for determining electrophoretic mobilities and diffusion coefficients of proteins [3], Diffusion coefficients can be measured from peak widths of analyte bands. The validity of the method was demonstrated by measuring the diffusion coefficients for dansylated amino acids and myoglobin. 

Y Walbroehl, J Jorgenson. Capillary zone electrophoresis for determination of electrophoretic mobilities and diffusion coefficients. J Microcolumn Separ 1 41, 1989. 

In CZE, the capillary, inlet reservoir, and outlet reservoir are filled with the same electrolyte solution. This solution is variously termed background electrolyte, analysis buffer, or run buffer. In CZE, the sample is injected at the inlet end of the capillary, and components migrate toward the detection point according to their mass-to-charge ratio by the electrophoretic mobility and separations principles outlined in the preceding text. It is the simplest form of CE and the most widely used, particularly for protein separations. CZE is described in Capillary Zone Electrophoresis. ... 

Since all electrophoretic mobility values are proportional to the reciprocal viscosity of the buffer, as derived in Chapter 1, the experimental mobility values n must be normalized to the same buffer viscosity to eliminate all other influences on the experimental data besides the association equilibrium. Some commercial capillary zone electrophoresis (CZE) instruments allow the application of a constant pressure to the capillary. With such an instrument the viscosity of the buffer can be determined by injecting a neutral marker into the buffer and then calculating the viscosity from the time that the marker needs to travel through the capillary at a set pressure. During this experiment the high voltage is switched off. 

Electromigration methods compose a family of analytical separation methods based on differences in the mobilities of charged analytes in the electric field. In this chapter, we discuss mainly such electromigration methods that are performed in thin capillaries with inner diameter (i.d.) <0.1 mm. These methods are commonly known as capillary electrophoretic methods where the most important modes are capillary zone electrophoresis (CZE), micellar electrokinetic capillary chromatography (MEKC), capillary gel electrophoresis (CGE), and capillary electrochromatography (CEC). 

The type of electrophoresis we have been discussing so far is called capillary zone electrophoresis. Separation is based on differences in electrophoretic mobility. If the capillary wall is negative, electroosmotic flow is toward the cathode (Figure 26-20) and the order of elution is cations before neutrals before anions. If the capillary wall charge is reversed by coating it with a cationic surfactant (Figure 26-24) and the instrument polarity is reversed, then the order of elution is anions before neutrals before cations. Neither scheme separates neutral molecules from one another. 

Jalali-Heravi, M., Shen, Y., Hassanisadi, M., and Khaledi, M. G. (2005). Prediction of electrophoretic mobilities of peptides in capillary zone electrophoresis by quantitative structure-mobility relationships using the Offord model and artificial neural networks. Electrophoresis 26,1874—1885. 

Capillary zone electrophoresis (CZE), also known as free-solution CE, is the most widely used mode of CE essentially because of its versatility. Protein separation in CZE is based on the differential electrophoretic mobility of the analytes. This mobility is primarily dependent on a protein s size and net charge, the charge-to-mass ratio. Solvent properties that influence the size and charge of a protein include pH, ionic strength, viscosity, and dielectric constant.67 Manipulation of these properties, most notably pH, dictates the selectivity in CZE. Maximizing the charge difference between two proteins via pH modification optimizes their separation. 

Capillary zone electrophoresis (CZE), micellar capillary electrokinetic chromatography (MECC), capillary gel electrophoresis (CGE), and affinity capillary electrophoresis (ACE) are CE modes using continuous electrolyte solution systems. In CZE, the velocity of migration is proportional to the electrophoretic mobilities of the analytes, which depends on their effective charge-to-hydrodynamic radius ratios. CZE appears to be the simplest and, probably, the most commonly employed mode of CE for the separation of amino acids, peptides, and proteins. Nevertheless, the molecular complexity of peptides and proteins and the multifunctional character of amino acids require particular attention in selecting the capillary tube and the composition of the electrolyte solution employed for the separations of these analytes by CZE. 

Capillary Zone Electrophoresis. The most fundamental approach that involves the use of a fused-silica capillary placed between the two buffer vials so that separation of the sample component occurs after an electric field (voltage) is applied to the system. Separation of the analytes is based on differences in electrophoretic mobility. Only charged compounds, both large and small, can be separated in this format. 

In practice, both electrophoretic methods have their advantages. Capillary isoelectric focusing enables rapid and precise determination of isoelectric points but provides no information on the general pH-dependence of mobility or pfCa values. In addition, because of its high efficiency cIEF can reveal impurities which are not detectable under the broader peaks of CZE (Fig. 31). Capillary zone electrophoresis, however, determines pi values only indirectly pKa characteristics can also be determined but this takes longer. 

A certain inorganic cation has an electrophoretic mobility of 4.31 X 10 " cm-s V . This same ion has a diffusion coefficient of 9.8 X 10 cm-s. If this ion is separated by capillary zone electrophoresis with a. 50.0-cm capillary, what is the expected plate count N at applied voltages of... 

Recently, Jalali-Heravi et al. (9,11) have developed a multivariable model in order to improve the predictive ability of the Offord model and understand the effects of further structural descriptors on electrophoretic mobility in capillary zone electrophoresis (CZE), in addition to charge and size. They generated a diverse data set based on a 125-peptide study, which ranges in size from 2 to 14 amino acids and charges of 0.743-5.843. The Pe of the peptides were measured in bare fused-silica capillaries in CZE mode using 50 mM sodium phosphate buffer at pH 2.5. The detection wavelength was 214nm and the separation temperature was 37 °C. 

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