Capillary electrochromatography: A review (original) (raw)

Capillary electrochromatography: An alternative to HPLC and CE

Journal of Separation Science, 2002

CEC is a technique that has attracted increased interest in recent years. It combines the advantages of high efficiency of electrophoretic separation methods with the greater selectivity characteristic of HPLC. In this paper we explore the use of CEC as a potential alternative to conventional HPLC, l-HPLC, and CE. Recent developments, both theoretical and experimental, are reviewed. The practical aspects of application of CEC in various modes of separation are also discussed.

Recent applications in capillary electrochromatography

Electrophoresis, 2001

The most recent and important applications in capillary electrochromatography (CEC) are summarized, covering literature published since May 2001. A selection of new developments in stationary phases for CEC is highlighted, and enantiomeric separations and chiral stationary phases are discussed. Also, CEC applications of biological molecules, pharmaceuticals, and applications in the field of industrial and environmental analysis are summarized. For this review three modes of CEC were taken into account, i.e., packed-column CEC, CEC using monolith technology, and open-tubular CEC.

Theory of capillary electrochromatography

Journal of Chromatography A, 2001

The present state of the theory of capillary electrochromatography (CEC) is reviewed. Emphasis is placed on electroosmosis and the electrical double layer, and the generally good understanding of the factors affecting the electroosmotic flow in CEC columns. The relation of CEC to other electrically driven separations are described, along with band broadening, and the influence of column temperature in CEC. The theoretical potential of CEC is assessed from the standpoint of current and future column technology, and likely future application areas are described.

Improved column preparation and performance in capillary electrochromatography

Journal of Chromatography A, 2000

Problems encountered in capillary electrochromatography, i.e. non-reproducible column manufacture, bubble formation during usage, short column lifetimes and limited choice of packing particles are addressed by the development of fritless or single-frit, internally tapered, segmented and dead-volume free coupled capillary columns. The Van Deemter plots measured demonstrate the performance of these high-quality capillaries which are suitable for capillary electrochromatography as well as for capillary high-performance liquid chromatographic applications.

Advances in column technology and instrumentation in capillary electrochromatography

Journal of Chromatography A, 2000

Capillary electrochromatography (CEC) is an emerging technique gaining increased interest. Improvement of instrumentation and column technology will be of prime importance for the further development of this technique and its use in validated methods. In this paper, developments in column technology and instrumentation for CEC are reviewed with emphasis on developments within the last 3 years. Attention is directed to the employment of stationary phases specifically designed for CEC, the use of soft and rigid gels in place of packings, fritless packed capillaries, column dimensions, the optimization of injection and detection parameters, and gradient elution CEC.

Semipreparative Capillary Electrochromatography

Analytical Chemistry, 2001

Capillaries with inner diameters of 550 µm have successfully been packed with 1.5-µm octadecyl silica particles using frits made of macroporous polymers by the UV photopolymerization of a solution of glycidyl methacrylate and trimethylolpropane trimethacrylate. This type of frit is found superior to one made of low-melting point poly-(styrene-co-divinylbenzene) beads. Bubble formation is not observed to occur within these capillary columns under our experimental conditions. Separations can be achieved with sample injection volumes as high as 1 µL. To demonstrate its semipreparative use, a mixture of 500 nL of taxol (20 mM) and its precursor, baccatin III (30 mM), is separated using such a column with a Tris buffer. Capillary electrochromatography (CEC) is a powerful separation technique that combines high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). It has attracted much interest in the past few years because it has (1) high separation efficiency, (2) high selectivity, (3) low solvent consumption, and (4) low operational costs. Recently, several research groups have presented many impressive applications of CEC. A broad variety of different species, such as corticosteroids, 1 amino acids, 2-4 proteins and peptides, 5-8 carbohydrates, 9 environmental contaminants, 10,11 natural products, 12,13 and pharmaceuticals, 14-16 have successfully been separated using CEC. Several

Analytical separations in open-tubular capillary electrochromatography

ELECTROPHORESIS, 2003

This review represents a summary of recent progress in open-tubular capillary electrochromatography (OT-CEC) for chiral and achiral separations. The OT-CEC approach is an alternative to packed-CEC that could eliminate the problems associated with retaining frits and silica particles. In OT-CEC, the stationary phase is immobilized on the inner walls of the capillary. Preparation of the stationary phase is critical for OT-CEC. The preparation methods for capillary columns include (i) adsorption, (ii) covalent bonding and/or cross-linking, (iii) porous layers, (iv) chemical bonding after etching, (v) sol-gel, and (vi) molecular imprinting. Major developments, potential applications, technical difficulties and advantages associated with these wall coatings in OT-CEC are presented. In addition, the coupling of OT-CEC with mass spectrometry (MS) is briefly reviewed. Several applications of this hyphenated technique for analytical separations are also summarized.

Capillary Electrochromatography A Versatile Tool for Biochemical Analysis

Capillary Electro chromatography (CEC) is a small scale separation technique which involves principle of both chromatography and capillary electrophoresis. Separation of analyte is done on the basis of differences in ratio of partition between stationary phase and mobile phase or due to differences in their electrophoretic mobility. Capillary Electro chromatography (CEC) combines the principles used in HPLC and CE. The mobile phases are driven across the chromatographic bed using electro osmosis instead of pressure (as in HPLC). This review describes the general introduction to CEC, the various advantages of CEC over HPLC and Electophoresis, instrumentation, history, various stationary phase and mobile phases, column technology and vast applications of CEC in a variety of fields.

Capillary Electrochromatography: A Powerful Tool for the Resolution of Complex Mixtures

Journal of AOAC INTERNATIONAL

Methods such as capillary electrophoresis (CE) and capillary liquid chromatography (LC) are particularly useful in the analysis of complex mixtures because of their high resolving power. Continued refinement of these techniques has led to a novel separation method known as capillary electrochromatography (CEC), also referred to as capillary electrokinetic chromatography, which is a combination of capillary LC and conventional CE. As in LC, mobile phase is transported through a column where partitioning of solutes occurs. In CEC, mobile phase flow is generated by electroosmosis, which arises when an electric potential is applied across the long axis of the capillary column. The favorable flow dynamics of electroosmosis result in higher chromatographic efficiencies in CEC relative to LC. If the species of interest are charged, a second separation mechanism is afforded by electrophoresis. CEC combines the high efficiency of capillary electrophoretic separations with the broad range of ...