Capillary zone electrophoresis development

Catechin and epicatechin are two flavanols of the catechin family. They are enantiomers. The capillary zone electrophoresis (CE) methods with UV-detection were developed for quantitative determination of this flavanols in green tea extracts. For this purpose following conditions were varied mnning buffers, pH and concentration of chiral additive (P-cyclodextrin was chosen as a chiral selector). Borate buffers improve selectivity of separation because borate can make complexes with ortho-dihydroxy groups on the flavanoid nucleus. 

Berzas Nevado, J.J. et al.. Method development and validation for the simultaneous determination of dyes in food stuffs by capillary zone electrophoresis. Anal. Chim. Acta, 378, 63, 1999. 

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. 

Capillary zone electrophoresis coupled with fast cyclic voltammetric detection was developed by Zhou et al. [27] for the separation and determination of OTC, TC, and CTC antibiotics. All compounds were well separated by optimization of pH and complexation with a boric acid sodium tetraborate buffer. The detection limit using fast on-line cyclic voltammetric detection with Hg-film-microm electrode was 1.5 x 10-6 mol/L for OTC (signal to noise ratio > 2). A continuous flow manifold coupled on-line to a capillary electrophoresis system was developed by Nozal et al. [28] for determining the trace levels of OTC, TC, and DC in surface water samples. 

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. 

C Miller, J Rivier. Peptide chemistry development of high performance liquid chromatography and capillary zone electrophoresis. Biopolymers (Pept Sci) 40, 265, 1996. 

For capillary zone electrophoresis (CZE) mass spectrometry coupling, another modification of an ESI interface has been developed. This interface uses a sheath flow of liquid to make the electrical contact at the CZE terminus, thus defining both the CZE and electrospray field gradients. This way, the composition of the electro sprayed liquid can be controlled independently of the CZE buffer, thereby providing operation with buffers that could not be used previously, e.g., aqueous and high ionic strength buffers. In addition, the interface operation becomes independent of the CZE flow rate. [62]... 

Kaale, E., Van Schepdael, A., Roets, E., and Hoogmartens, J. (2001). Development and validation of a simple capillary zone electrophoresis method for the analysis of kanamycin sulfate with UV detection after pre-capillary derivatization. /. Chromatogr. A 924(1—2), 451—458. 

Cherkaoui, S., Mateus, L., Christen, P., and Veuthey, J.-L. (1997). Development and validation of a capillary zone electrophoresis method for the determination of atropine, homatropine and scopolamine in ophthalmic solutions.. Chromatogr. B 696(2), 283-290. 

Patterson, S. C., Ramstad, T., and Mills, K. A. (2005). Development and validation of a procedure for the determination of minoxidil in hair-regrowth formulations using two variants of capillary zone electrophoresis. II Farmaco 60(6—7), 547—554. 

Dedicated applications of capillary zone electrophoresis (CZE) coupled to MS are discussed, particularly in the field of drug analysis. Development of other capillary-based electrodriven separation techniques such as non-aqueous capillary electrophoresis (NACE), micellar electrokinetic chromatography (MEKC), and capillary electrochromatography (CEC) hyphenated with MS are also treated. The successful coupling of these electromigration schemes with MS detection provides an efficient and sensitive analytical tool for the separation, quantitation, and identification of numerous pharmaceutical, biological, therapeutic, and environmental compounds. 

A determination of PQQ by capillary zone electrophoresis was also developed <2000JCH(739)101>. The optimal separation conditions were a 50mM /3-alanine HCl pH 3.0 buffer, an applied voltage of 25 kV (negative polarity), and a temperature of 25 °C. The linear detection range for concentration versus peak area is that this assay is from 5 to 500 mM with a detection limit of 0.1-0.2 mM. 

Among the electrophoretic methods of chiral resolution, various forms of capillary electrophoresis such as capillary zone electrophoresis (CZE), capillary isotachophoresis (CIF), capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), affinity capillary electrophoresis (ACE), and separation on microchips have been used. However, in contrast to others, the CZE model has been used frequently for this purpose [44]. On the other hand, drawbacks associated with the electrophoretic technique due to lack of development of modem chiral phases have limited the application of these methods. Moreover, the electrophoretic techniques cannot be used at the preparative scale, which represents an urgent need of chiral separation science. 

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