Capillary zone electrophoresis potential

Owing to their high separation efficiency, the potential for using micellar electro-kinetic chromatography and capillary zone electrophoresis (CZE) ... 

Capillary electrophoresis (CE) or capillary zone electrophoresis (CZE) is the technique most often employed in pesticide residue analysis. In its most basic form, free zone electrophoresis, a fused-silica capillary is filled with electrolyte (running buffer or background electrolyte). A potential is applied across the capillary and the cations... 

Table 1 summarizes several of the experimental methods discussed in this chapter. A need exists for new or revised methods for transport experimentation, particularly for therapeutic proteins or peptides in polymeric systems. An important criterion for the new or revised methods includes in situ sampling using micro techniques which simultaneously sample, separate, and analyze the sample. For example, capillary zone electrophoresis provides a micro technique with high separation resolution and the potential to measure the mobilities and diffusion coefficients of the diffusant in the presence of a polymer. Combining the separation and analytical components adds considerable power and versatility to the method. In addition, up-to-date separation instrumentation is computer-driven, so that methods development is optimized, data are acquired according to a predetermined program, and data analysis is facilitated. 

The charge on the liposomal surface is a property that has major effects on the stability, biodistribution, and cellular uptake of liposomes, and is governed by lipid headgroup composition and by pH. It can be monitored by micro electrophoresis (i.e., capillary zone electrophoresis), or by measurement of the zeta potential (Egorova, 1994). 

Direct control of the EOF in capillary zone electrophoresis can be obtained by using an external electric field. The EOF may be increased, decreased, or even reversed in the fused silica capillaries by the application of a separate potential field across the wall of the capillary. Further, the zeta potential can be changed at any time during the analysis to achieve innovative separation results. 

Capillary electrophoresis (CE) with ICP-MS detection is a technique that first started to receive attention in 1995 [100-102]. There are several modes of CE, including capillary zone electrophoresis (CZE), capillary gel electrophoresis (CGE), micellar electrokinetic chromatography (MEKC), capillary isoelectric focusing (CIEF), and capillary isotacophoresis. Capillary zone electrophoresis is the most common mode of CE to be used with ICP-MS detection to date, although coupling of other modes with ICP-MS may have significant potential. 

CE has many separation modes that are beneficial to protein impurity analysis. Within the many thousands of potential protein impurities in a recombinant product there will be several that have only minor physicochemical differences from the drug product. The application of different CE modes can potentially resolve these impurities. CE methods can be divided into four principle modes that are applicable to recombinant protein impurity analysis capillary zone electrophoresis, capillary isoelectric focusing, capillary gel electrophoresis, and micellar electrokinetic capillary chromatography. Each mode will be discussed briefly. Since the technology is so young and still very exploratory, CE methods are developed empirically for specific separations. It is difficult to provide standard protocols for CE impurity analysis. Instead, protocols that can be used as a starting point for impurity analysis will be provided as well as the citation of examples of impurity analyses from the literature to provide additional sources of protocols for interested readers. 

Frenz, J., Battersby, J., and Hancock, W. S. (1990). An examination of the potential of capillary zone electrophoresis for the analysis of polypeptide samples. Pept. Chem., Struct. Biol., Proc. 11th Am. Pept. Symp., p. 430. 

An approach suitable for drug screening alternative to MEKC was proposed by Chee and Wan (1993), who used capillary zone electrophoresis (CZE) with 50 mAf phosphate buffer pH 2.35 in a 75 / m i.d. (60 cm long) bare silica capillary. In 11 minutes, they achieved the separation of 17 basic drugs of potential forensic interest methapyrilene, brompheniramine, amphetamine,... 

Sommer, L., Vlasankova, R. Survey of the potential of high-performance liquid chromatography and capillary zone electrophoresis for the determination of platinum and platinum-group metals. Chromatographia 52, 692-702 (2000)... 

B. Gas, M. Stedry, and E. Kenndler, Contribntion of the electroosmotic flow to peak broadening in capillary zone electrophoresis with nniform zeta potential, J. Chro-matogr A 709 63 (1995). 

B. Potocek, B. Gas, E. Kenndler, and M. Stedry, Electroosmosis in capillary zone electrophoresis with non-uni-form zeta potential, 7. Chromatogr. A 709 51 (1995). 

The dependence of these electrokinetic velocities on pH is shown in Fig. 1. In the case of capillary zone electrophoresis (CZE), with a bare fused-silica capillary, the pH greatly affects the EOF velocity (i.e., i eof significantly decreases with the decrease in pH from 8 to 3). In MEKC, however, the dependence of i eof on pH is different from that in CZE, especially under weakly acidic conditions (pH 7.0-5.5). In the range of pH between 7.0 and 5.5, qf slightly decreases with the decrease in pH, due to the adsorption of the SDS molecule or monomer on the inside wall of the capillary. On the other hand, of rapidly decreases with the decrease in the pH below 5.5. The decrease of qf is mainly caused by the decrease in the zeta-potential of the inside wall of the capillary, because the dissociation of silanol groups on the capillary wall is more suppressed as the solution becomes more acidic. 

Direct measurement of riboflavin, FMN, and FAD in plasma or erythrocytes may be made by HPLC, usually with fluorescence detection after protein precipitation or by capillary zone electrophoresis with laser-induced fluorescence detection (CZE-LIF). In a study of riboflavin status and FMN and FAD concentrations in plasma and erythrocytes from elderly subjects at baseline and after low-dose riboflavin supplementation, using both activation coefficient measurements and CE-LIF, it was concluded that concentrations of aU Ba vitamers except plasma FAD are potential... 

R Kuhn, J Wagner, Y Walbroehl, T Bereuter. Potential and limitations of an optically active crown ether for chiral separation in capillary zone electrophoresis. Electrophoresis 15 828-834, 1994. 

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