Capillary electrophoresis modes

Capillary electrophoresis (CE) has several unique advantages compared to HPLC, snch as higher efficiency dne to non-parabolic fronting, shorter analytical time, prodnction of no or much smaller amounts of organic solvents, and lower cost for capillary zone electrophoresis (CZE) and fused-silica capillary techniques. However, in CZE, the most popular separation mode for CE, the analytes are separated on the basis of differences in charge and molecular sizes, and therefore neutral compounds snch as carotenoids do not migrate and all co-elute with the electro-osmotic flow. 

In the previously described electrophoretic methods, the capillary was filled with electrolytes only. Another mode of operation in capillary electrophoresis involves filling the capillary with gel or viscous polymer solutions. If desired, a column can be packed with particles and equipped with a frit.68 This mode of analysis has been favorably used for the size determination of biologically important polymers, such as DNA, proteins, and polysaccharides. The most frequently used polymers in capillary gel electrophoresis are cross-linked or linear polyacrylamide,69 cellulose derivatives,70-75 agarose,76 78 and polyethylene glycols. 

Suzuki, S., Kakehi, K., and Honda, S., Two-dimensional mapping of N-gly-cosidically linked asialo-oligosaccharides from glycoproteins as reductively pyridylaminated derivatives using dual separation modes of high-performance capillary electrophoresis, Anal. Biochem., 205, 227, 1992. 

Fan et al. [106] developed a high performance capillary electrophoresis method for the analysis of primaquine and its trifluoroacetyl derivative. The method is based on the mode of capillary-zone electrophoresis in the Bio-Rad HPE-100 capillary electrophoresis system effects of some factors in the electrophoretic conditions on the separation of primaquine and trifluoroacetyl primaquine were studied. Methyl ephedrine was used as the internal standard and the detection was carried out at 210 nm. A linear relationship was obtained between the ratio of peak area of sample and internal standard and corresponding concentration of sample. The relative standard deviations of migration time and the ratio of peak area of within-day and between-day for replicate injections were <0.6% and 5.0%, respectively. 

Identification and quantification of natural dyes need high performance analytical techniques, appropriate for the analysis of materials of complicated matrices containing a small amount of coloured substances. This requirement perfectly fits coupling of modern separation modules (usually high performance liquid chromatography in reversed phase mode, RPLC, but also capillary electrophoresis, CE) with selective detection units (mainly mass spectrometer). 

Also, specific chapters deal with the use of CL reactions as detection mode in FIA (Chapter 12), in separational techniques, such as liquid chromatography (LC) (Chapter 14) or capillary electrophoresis (CE) (Chapter 15), in immunoassay (Chapter 18), and in the development of sensors (Chapter 20). The recent use of this technique for the analysis of DNA (Chapter 19) and a photosensitized CL mode for medical routine and industrial applications (Chapter 17) are also considered in this book. 

This section deals briefly with classical methods based on conventional mixing of the sample and reagents such as the batch mode and low-pressure flow mixing methods, as well as the use of CL detection in continuous separation techniques such as liquid chromatography and capillary electrophoresis for comparison with the unconventional mixing mode. 

Reversed-phase HPLC can be compared in terms of its utility with other modes of chromatography and with other separation techniques such as gel electrophoresis, capillary electrophoresis (CE), and capillary electrochromatography. 

Chiral separation of drng molecules and of their precursors, in the case of synthesis of enantiomerically pure drugs, is one of the important application areas of HPLC in pharmaceutical analysis. Besides HPLC, capillary electrophoresis (CE) is another technique of choice for chiral separations. Chapter 18 provides an overview of the different modes (e.g., direct and indirect ones) of obtaining a chiral separation in HPLC and CE. The direct approaches, i.e., those where the compound of interest is not derivatized prior to separation, are discussed in more detail since they are cnrrently the most frequently used techniques. These approaches require the use of the so-called chiral selectors to enable enantioselective recognition and enantiomeric separation. Many different molecnles have been nsed as chiral selectors, both in HPLC and CE. They can be classified into three different groups, based on their... 

The origins, principles, methods, and modes of capillary electrophoresis (CE) are discussed. Massive application of electrophoresis methods started after Tiselius s moving boundary method that was optimized by the use of paper or a gel as a semiconducting medium. The applications of paper and gel electrophoresis were situated mostly in the biochemical environment for the analysis of proteins, amino... 

THEORETICAL CONSIDERATIONS IN PERFORMANCE OF VARIOUS MODES OF CE TABLE I Instrumentation for Capillary Electrophoresis... 

Qualification of a capillary electrophoresis instrument is performed using failure mode, effects, and criticality analysis as the risk analysis tool. The instrument is broken down into its component modules and the potential failures of those components identified. The potential effect of those failures is defined and the risk characterized. Any current evaluation of those failures is identified and any recommended actions to mitigate the risk defined. 

After a short introduction into the relevance of Impurity profiling for regulatory authorities, public health, and the pharmaceutical industry, an overview is presented based on the various modes of capillary electrophoresis that have been used in drug impurity analysis. The applications of capillary zone electrophoresis, non-aqueous capillary electrophoresis, micellar electrokinetic capillary chromatography, microemulsion electrokinetic capillary chromatography, capillary gel electrophoresis, and capillary electrochromatography are presented consecutively. 

Marsh, A., Clark, B. J., and Altria, K. D. (2004). Orthogonal separations of nicotine and nicotine-related alkaloids by various capillary electrophoretic modes. Electrophoresis 25, 1270—1278. 

Capillary zone electrophoresis (CZE) is the most common electrophoretic separation technique due to its simplicity of operation and its flexibility. It is the standard mode for drug analysis, identification of impurities, and pharmacokinetic studies. Other separation modes, such as capillary isotachopho-resis (CITP), micellar electrokinetc chromatography (MEKC), capillary electrochromatography (CEC), capillary gel electrophoresis (CGE), capillary isoelectric focusing, and affinity capillary electrophoresis (ACE), have then-advantages in solving specific separation problems, since the separation mechanism of each mode is different. 

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