Miceller electrokinetic chromatography

ON-LINE CONCENTRATION TECHNIQUES IN MICELLE ELECTROKINETIC CHROMATOGRAPHY (MEKC)... 

MCN microconcentric nebulizer MEGA molecular emission cavity analysis MEKC micelle electrokinetic chromatography... 

It is clear that this type of system could be also used with some slight modification for the separation of enantiomers. This type of separation has been termed miceller electrokinetic chromatography [1]. Watarai [2] carried the concept further and used a micro emulsion to the same purpose and termed the technique micro emulsion electrokinetic chromatography. In chiral, capillary electrophoresis, the chiral selector can also be an additive to the electrolyte, or take the form of an emulsion or be immobilized on the capillary tube surface as a traditional type of stationary phase. 

Although peptides, proteins, polysaccharides and certain polymers have been used successfully in LC to separate chiral substances, they have found only limited use in miceller electrokinetic chromatography. Due to the large number of different chiral, dispersive and polar sites available... 

Miceller Electrokinetic Chromatography (MEKC) This mode of CE is a... 

CE provides a complementary approach to HPLC separation. It is performed in several different formats, including capillary zone electrophoresis, miceller electrokinetic chromatography, capillary gel electrophoresis, capillary isoelectric focusing, isotachophoresis, and capillary electrochromatography. Of these formats, capillary zone electrophoresis is the most popular separation technique. The most successful coupling of CE with mass spectrometry is achieved via an ESI interface. The three most practical designs are sheathless interface, sheath-flow interface, and liquid-junction interface. 

The elution order for neutral species in MEKC depends on the extent to which they partition into the micelles. Hydrophilic neutrals are insoluble in the micelle s hydrophobic inner environment and elute as a single band as they would in CZE. Neutral solutes that are extremely hydrophobic are completely soluble in the micelle, eluting with the micelles as a single band. Those neutral species that exist in a partition equilibrium between the buffer solution and the micelles elute between the completely hydrophilic and completely hydrophobic neutrals. Those neutral species favoring the buffer solution elute before those favoring the micelles. Micellar electrokinetic chromatography has been used to separate a wide variety of samples, including mixtures of pharmaceutical compounds, vitamins, and explosives. 

R., Khaledi, M. G. Quantitative structure-activity relationships studies with micellar electrokinetic chromatography. Influence of surfactant type and mixed micelles on estimation of hydrophobicity and bioavailability. J. Chromatogr. A 1996, 727, 323-335. 

Micellar electrokinetic chromatography is based on the effects of the interaction of the analyte with surfactant micelles on the electrophoretic process. 

Besides CZE and NACE, micellar electrokinetic chromatography (MEKC) is also widely used, and ionic micelles are used as a pseudo-stationary phase. MEKC can therefore separate both ionic and neutral species (see Chapter 2). Hyphenating MEKC with ESI/MS is problematic due to the non-volatility of micelles, which contaminate the ionization source and the MS detector, resulting in increased baseline noise and reduced sensitivity. However, MEKC—ESI/MS was applied by Mol et al. for identifying drug impurities in galantamine samples. Despite the presence of non-volatile SDS, all impurities were detected with submicrogram per milliliter sensitivity and could be further characterized by MS/MS. 

Micellar electrokinetic chromatography is a hybrid of electrophoresis and chromatography. Introduced by Terabe in 1984 (9), MEKC is one of the most widely used CE modes. Ionic micelles, formed from surfactants added... 

Electrokinetic chromatography (EKC) using microemulsion is one of the most powerful tools for the rapid measurement of log P w with high reproducibility. Because it is relatively easy to manipulate the pseudostationary phases of EKC, a lot of phases have been reported for the measurement not only of physicochemical properties but also of the separation selectivity, such as polymer micelles (64) and double-chain surfactant vesicles (56-58,60,61). These phases are also interesting in terms of the correlation to bioactivity. 

N Chen, Y Zhang, S Terabe, T Nakagawa. Effect of physicochemical properties and molecular structure on the micelle—water partition coefficient in micellar electrokinetic chromatography. J. Chromatogr. A 678 327-332 (1994). 

M Hong, BS Weekley, SJ Grieb, JP Foley. Electrokinetic chromatography using thermodynamically stable vesicles and mixed micelles formed from oppositely charged surfactants. Anal. Chem. 70 1394-1403 (1998). 

S Terabe, M Shibata, Y Miyashita. Chiral separation by electrokinetic chromatography with bile-salt micelles. J Chromatogr A 480 403-411, 1989. 

D. Electrokinetic Chromatography of Drugs with Micelles or Oil Droplets as Interacting Phase... 

Figure 26-33 Separation of enantiomers of eight p blocker drugs by micellar electrokinetic chromatography at pH 8.0 in a 120-cm capillary at 30 kV. Micelles were formed by a polymer surfactant containing L-leucinate substituents for chiral recognition. The structure of one compound is shown. [From C. Akbay. S, A. A. Rizvi. and S. A. Shamsi, "Simultaneous Enantiosepcration and Tandem UV-MS Detection of Eight p-Blockers in Micellar Electrokinetic Chromatography Using a Chiral Molecular Micelle Anal. Chem. 2005, 77.1672.]...

Micellar electrokinetic chromatography is a form of chromatography because the micelles behave as a pseudostationary phase. Separation of neutral molecules is based on partitioning between the solution and the pseudostationary phase. The mass transfer term Cux is no longer 0 in the van Deemter equation 26-7, but mass transfer into the micelles is fairly fast and band broadening is modest. 

The water-soluble vitamins niacinamide (a neutral compound), riboflavin (a neutral compound), niacin (an anion), and thiamine (a cation) were separated by micellar electrokinetic chromatography in 15 mM borate buffer (pH 8.0) with 50 mM sodium dodecyl sulfate. The migration times were niacinamide (8.1 min), riboflavin (13.0 min), niacin (14.3 min), and thiamine (21.9 min). What would the order have been in the absence of sodium dodecyl sulfate Which compound is most soluble in the micelles ... 

The Effect of SDS Micelle on the Rate of a Reaction, J. Chem. Ed. 1992, 69, 1024 C. P. Palmer, Demonstrating Chemical and Analytical Concepts Using Electrophoresis and Micellar Electrokinetic Chromatography, J. Chem. Ed 1999, 76, 1542. 

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