Micellar electrokinetic chromatography modifications

Capillary electrophoresis (CE) coupled to MS has the advantage of high resolution and soft ionization for biomolecules, which may be used to differentiate post-translational modifications and variants of intact proteins and oligonucleotides. Different modes of CE (capillary zone electrophoresis, capillary isoelectric focusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as online preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) are used to compensate for the restricted detection sensitivity of the CE methodology [77, 78]. 

Another modification of CE is micellar electrokinetic chromatography (MEKC), which is widely used for the separation of nonpolar compounds. The molecules in question partition into micelles (nonpolar layer) with mechanisms similar to those observed with reverse-phase chromatography. An anionic surfactant, sodium dodecyl sulfate, is commonly used as a micellar... 

Capillary electrophoresis (CE) has emerged as an efficient and rapid separation technique in recent years. Its high efficiency has been employed in many applications such as in the analysis of environmental pollutants.Different approaches have been adopted to enhance selectivity for the analysis of different types of compounds. There are two approaches most commonly used to improve CE separations the addition of modifiers into the electrophoretic medium and the modification of the column. Examples of the first approach include the addition of surfactants into the electrophoretic medium as in micellar electrokinetic chromatography (MEKC), and the use of organic solvents,cyclodextrines, " " or bile salts " as buffer modifiers. Examples of the second method include the use of gel-filled columns (capillary gel electrophoresis) " and the coating of the capillary wall surface. " " ... 

In 1984. Terabe and collaboratorsdescribed a modification of CE that permitted the separation of low-moleeular-mass aromatic phenols and nitro compounds with equipment such as shown in Figure 30-1. Micellar electrokinetic chromatography (MEKC) is a type of CE that offers several unique features. Like CE, MEKC provides highly efficient separations on microvolumes of sample solution without the need for... 

CE can be operated in several modes. The approach described in the previous paragraph is referred to as capillary zone electrophoresis, or CZE. A variant called capillary gel electrophoresis uses a capillary tube filled with gel, essentially a miniaturized version of slab-gel techniques. The third variant, and the one of most forensic significance, is micellar electrokinetic chromatography (MEK or MECK). MEK is a modification designed to improve the separation of neutral spedes, which are easily separated from cations and anions, but not well separated among themselves. 

Capillary Electrochromatography. Capillary electrochromatography (CEC) is a hybrid technique that works on the basic principles of capillary electrophoresis and chromatography [41], This mode of chromatography is used on either packed or tubular capillaries/columns. The packed column approach was introduced by Pretorius et al. [60] in 1974, while open tubular CEC was presented by Tsuda et al. [61] a decade later. In 1984 Terabe et al. [62] introduced another modification in liquid chromatography, micellar electrokinetic capillary... 

This mouthful of words describes a form of capillary electrophoresis that separates neutral molecules as well as ions (Figure 23-21). The key modification in micellar electrokinetic capillary chromatography is the use of micelles in the capillary solution. Micelles are described in Box 23-2, which you should read now. 

Capillary zone electrophoresis (CE) is a relatively new analytical method currently under investigation for use in research and control laboratories for the analysis of ionic forms of vitamins. Micellar electrokinetic capillary chromatography (MECC) is a modification of CE which allows the separation of both neutral and ionic forms using buffers with micellar additives. Both methods have been used to separate water-soluble vitamins but very rarely pantothenic acid, which has only been analyzed by this technique in model mixtures and pharmaceuticals. 

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