Background -- Capillary electrophoresis chromatography(CEC) is a relatively new technique. It is and is used primarily for teaching. Capillary Electrophoresis (CE) and Capillary Electrochromatography (CEC) are both modern analytical techniques which have been developed in recent years and have been applied to a wide range of application areas.
Protocols and Procedures -- Details on the specific equipment in use within as well as working procedures and protocols have been developed.
Applications -- Thousands of instruments are now in use for the analysis of pharmaceuticals, DNA, proteins, peptides, clinical and forensic samples, agrochemicals, fine chemicals and natural products. It has high efficiency and resolution, rapid analysis time, plus minimal sample and solvent requirements, is an established technique in many laboratories. Its flexibility covers a broad range of applications in a wide variety of industries, from drug discovery and development through quality control and ion analysis. Agilent Technologies (formerly H-P) pioneered the development of this technique with the Agilent Capillary Electrophoresis system. Innovations include diode array detection in CE, the extended light-path capillaries, automated fraction collection, capillary electroc hromatography (CEC), the high sensitivity detection cell, and a fully integrated way to use CE-MS.
Capillary electrochromatography (CEC) is a rapidly evolving hybrid technique between HPLC and CE. In essence CE capillaries are packed with HPLC packing and a voltage is applied across the packed capillary which generates an electro-osmotic flow (EOF) [for example of EOF see the CE theory page of this website). The EOF transports solutes along the capillary towards the detector. Both differential partitioning and electrophoretic migration of the solutes occurs during their transportation towards the detector which leads to CEC separations. It is therefore possible to obtain unique separation selectivities using CEC compared to both HPLC and CE. The beneficial flow profile of EOF reduces flow related band broadening and separation efficiencies of several hundred thousand plates per meter are often obtained in CEC. There is no back pressure when EOF occurs so small particle sizes such as 1-3 micron can be used to improve separation efficiencies. Generally, carrier electrolytes containing high levels (40-80%) of organic solvents such as methanol or acetonitrile are employed in CEC which means it is useful for water-insoluble compounds which can be difficult to analyze by CE. The instrument used in CEC is identical to that used in CE - see below except that a packed capillary is used.
Example -- For the identification of reducing mono- and disaccharides at micromolar concentrations, MEKC of 4-aminobenzonitrile (4-ABN) derivatives with UV detection at 280 nm was shown to resolve most common saccharides. This technique was applied to a mixture of common mono- and disaccharides as shown in the figure. Derivatization is easily accomplished by combining the reagents with aqueous solutions of standards and heating in a sealed vial at 90° C for 15 minutes. The technique does not apply to non-reducing sugars such as sucrose.
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