Micellar Electrokinetic Capillary Chromatography MEKC

MECC, MEKC Micellar electrokinetic capillary chromatography... 

Different separation mechanisms, which determine selectivity, can be exploited in HPCE by appropriate choice of operating conditions. There are four principal modes of operation (Table 4.22) and it should be noted that in only one, micellar electrokinetic capillary chromatography (MEKC), is it possible to separate neutral species from one another. 

Micellar electrokinetic capillary chromatography (MEKC or MECC) is a more versatile technique than CZE due to its ability to separate neutral as well as ionic species. The term chromatography is used because a surfactant added to the buffer solution forms spherical aggregates of molecules... 

In order to separate neutral compounds, Terabe et al. [13] added surfactants to the buffer electrolyte. Above their critical micellar concentration (cmc), these surfactants form micelles in the aqueous solution of the buffer electrolyte. The technique is then called Micellar electrokinetic capillary chromatography, abbreviated as MECC or MEKC. Micelles are dynamic structures consisting of aggregates of surfactant molecules. They are highly hydrophobic in their inner structure and hydrophilic at the outer part. The micelles are usually... 

The next important milestone in CE was achieved in 1984, when Terabe et al. described the method of micellar electrokinetic capillary chromatography (MECC or MEKC). By simply adding a surfactant to the separation buffer electrolyte, it was possible to separate both charged and neutral compounds simultaneously in CE. Erom this point on, the technique developed rapidly with many applications resulting in a demand for identification information. Coupling of CE to mass spectrometry was a next challenge and the... 

ILC, immobilized liposome chromatography MEKC, micellar electrokinetic capillary chromatography. 

A method is described for extraction and determination of sildenafil citrate and its metabolites in human serum by micellar electrokinetic capillary chromatography (MEKC) coupled with sample stacking and polarity switching <2002JCH279>. 

Electromigration methods compose a family of analytical separation methods based on differences in the mobilities of charged analytes in the electric field. In this chapter, we discuss mainly such electromigration methods that are performed in thin capillaries with inner diameter (i.d.) <0.1 mm. These methods are commonly known as capillary electrophoretic methods where the most important modes are capillary zone electrophoresis (CZE), micellar electrokinetic capillary chromatography (MEKC), capillary gel electrophoresis (CGE), and capillary electrochromatography (CEC). 

Micellar electrokinetic chromatography (MEKC) is a modality of liquid chromatography having a surfactant molecule in the form of a micelle, which was introduced by Terabe et al. in 1984 [38]. The formation and separation occur in the capillary and, hence, it is also called micellar electrokinetic capillary chromatography (MECC). This modality is useful for some specific molecules having solubilities in micelles and, therefore, utilized for the separation and identification of such compounds with great efficiency, reproducibility, and low levels of detections. The most commonly used compounds for micelle formation are sodium dodecyl sulfate (SDS), sodium tetradecyl sulfate, sodium decanesulfonate, sodium /V-lauryl-/V-mcthyllauratc, sodium... 

Many pharmaceutical preparations contain multiple components with a wide array of physico-chemical properties. Although CZE is a very effective means of separation for ionic species, an additional selectivity factor is required to discriminate neutral analytes in CE. Terabe first introduced the concept of micellar electrokinetic capillary chromatography (MEKC) in which ionic surfactants were included in the running buffer at a concentration above the critical micelle concentration (CMC) [17], Micelles, which have hydrophobic interiors and anionic exteriors, serve as a pseudostation-ary phase, which is pumped electrophoretically. Separations are based on the differential association of analytes with the micelle. Interactions between the analyte and micelles may be due to any one or a combination of the following electrostatic interactions, hydrogen bonding, and/or hydro-phobic interactions. The applicability of MEKC is limited in some cases to small molecules and peptides due to the physical size of macromolecules... 

Here free solution indicates capillary electrophoresis carried out in a solution without any additives SDS-PAGE is sodium dodecyl sulfate-polyacrylamide gel electrophoresis MECC is micellar electrokinetic capillary chromatography, at times, also called MEKC (micellar electrokinetic chromatography). 

The first reports of micellar electrokinetic capillary chromatography (MECC or MEKC) appeared in the literature in 1984 [16]. Through April 2002, there have been over 1100 English-language papers published in the field. The subject is covered in all general textbooks on capillary electrophoresis. While a vast number of surfactants and related reagents can be employed, most separations can be accomplished with a few simple recipes. 

Capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) are the most common CE modes used in determining barbiturates. We will discuss them separately. 

Micelles and cyclodextrins are the most common reagents used for this technique. Micellar electrokinetic capillary chromatography (MECC or MEKC) is generally used for the separation of small molecules [6], Sodium dodecyl sulfate at concentrations from 20 to 150 mM in conjunction with 20 mM borate buffer (pH 9.3) or phosphate buffer (pH 7.0) represent the most common operating conditions. The mechanism of separation is related to reversed-phase liquid chromatography, at least for neutral solutes. Organic solvents such as 5-20% methanol or acetonitrile are useful to modify selectivity when there is too much retention in the system. Alternative surfactants such as bile salts (sodium cholate), cationic surfactants (cetyltrimethy-lammonium bromide), nonionic surfactants (poly-oxyethylene-23-lauryl ether), and alkyl glucosides can be used as well. 

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