Capillary Electrophoretic Separation Methods

An exeuaple of a nodular apparatus for capillary electrophoretic separation methods, is shown in Figure 4.43 [637-639,681-684]. It Offers a choice of automated sample introduction methods with on-column detection and has a... 

Nishi et al. [110] used dextran and dextrin as chiral selectors in capillary-zone electrophoresis. Polysaccharides such as dextrins, which are mixtures of linear a-(l,4)-linked D-glucose polymers, and dextrans, which are polymers of D-glucose units linked predominantly by a-(l,6) bonds, have been employed as chiral selectors in the capillary electrophoretic separation of enantiomers. Because these polymers are electrically neutral, the method is applicable to ionic compounds. The enantiomers of basic or cationic drugs such as primaquine were successfully separated under acidic conditions. The effects of molecular mass and polysaccharide concentration on enantioselectivity were investigated. 

Miiller et al., 2000 Her et al., 2003). Emphasis has been placed on (a) the use of gel chromatography or gel permeation chromatography for the fractionation of DOM on the basis of molecular size differences and (b) the application of electrophoretic separation methods (Perminova et al., 1998,2003 Specht and Frimmel, 2000), including electrophoresis, capillary electrophoresis (CE), isotachophoresis, isolelectric focusing,polyacrylamide gel electrophoresis (PAGE), and capillary zone electrophoresis (CEZ) (De Nobili et al., 1989,1998 Schmitt-Kopplin et al., 1998). 

Elaboration of new electrophoretic methods for PolyP separation is continuing. For example, capillary electrophoretic separations of sodium PolyPs with chain lengths of 5 to 44 has been reported. In this work, a buffer containing pyromellitic acid, triethanolamine and hexamethonium hydroxide gives high-resolution separation of linear and cyclic PolyPs (Stover, 1997 Wang and Li, 1998). 

Capillary electrophoretic separation of nucleic acids has been reviewed (Cohen et al., 1987a Kuhr, 1990 Gebauer and Thormann, 1991). In nucleotide and nucleoside analysis, MEKC has been the method of choice, using SDS (Row et al. 1987 Cohen et al., 1987b Kasper et al., 1988), dodecyltrimethylammonium bromide, or hexadecyltriethylammonium bromide (Liu et al., 1989). Other applications concerning chemically modified nucleotides, nucleosides, and nucleobases can be found in papers by Lecoq et al. (1991) and Thormann et al. (1992). 

Thormann, W., Firestone, M.A. (1989) Capillary electrophoretic separations, in Protein Purification - Principles, High Resolution Methods, and Applications (Janson, J.-C., Ryden, L., Eds.). VCH, Weinheim. 

In their simplest form, capillary electrophoretic separations are based on differences in the charge-to-size ratios of the analytes. The initial consideration for CE is, therefore, to find conditions under which ionization of the analytes is achieved. As noted by Altria, for acids or bases, ionization can typically be achieved under one of two sets of conditions in phosphate buffer (pH 2.5) for bases or in borate buffer (natural pH 9.3) for acids. Use of these two sets of conditions provides a generic approach to method development and has been shown to be viable for a wide range of sample types. For pharma-... 

JaworskaM., Szulinska G, WiUc M., Tautt J., Capillary electrophoretic separation of IV-acetylcysteine and its impurities as a method for quality control of pharmaceuticals. J. Chromatogr. A, 853,479-485 (1999). 

Hjerten S (1996) Capillary electrophoretic separation in open and coated tubes with special reference to proteins. Methods in Enzytnology 270 296-319. 

The methodical limitations concern analyte recovery (in the case of peak-area-changes assays), peak identification, and in understanding the interplay between binding rates and separation parameters. Perhaps the most limiting factor for using the technique outside specialist laboratories is the fact that ACE is not one, but a suite of different techniques united by a capillary electrophoretic separation step. Furthermore, in the case of unknown stoichiometry, only absolute dimensions of the binding constants are accessible. 

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. 

Lin et al. [95] used capillary electrophoresis with dual cyclodextrin systems for the enantiomer separation of miconazole. A cyclodextrin-modified micellar capillary electrophoretic method was developed using mixture of /i-cyclodextrins and mono-3-0-phenylcarbamoyl-/j-cyclodextrin as chiral additives for the chiral separation of miconazole with the dual cyclodextrins systems. The enantiomers were resolved using a running buffer of 50 mmol/L borate pH 9.5 containing 15 mmol/L jS-cyclodextrin and 15 mmol/L mono-3-<9-phcnylcarbamoyl-/j-cyclodextrin containing 50 mmol/L sodium dodecyl sulfate and 1 mol/L urea. A study of the respective influence of the /i-cyclodcxtrin and the mono-3-(9-phenylcarbamoyl-/i-cyclodextrin concentration was performed to determine the optical conditions with respect to the resolution. Good repeatability of the method was obtained. 

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