Chromatography, liquid micellar electrokinetic capillary

S Y Yang, MG Khaledi. Linear solvation energy relationships in micellar liquid chromatography and micellar electrokinetic capillary chromatography. J Chromatogr 692 301-310, 1995. 

Salo, M., Siren, H., Volin, P., Wiedmer, S. and Vuorela, H. (1996) Structure-retention relationships of steroid hormones in reversed phase liquid chromatography and micellar electrokinetic capillary chromatography. 

Kovat s retention index (p. 575) liquid-solid adsorption chromatography (p. 590) longitudinal diffusion (p. 560) loop injector (p. 584) mass spectrum (p. 571) mass transfer (p. 561) micellar electrokinetic capillary chromatography (p. 606) micelle (p. 606) mobile phase (p. 546) normal-phase chromatography (p. 580) on-column injection (p. 568) open tubular column (p. 564) packed column (p. 564) peak capacity (p. 554)... 

Recently a new method was developed for the complete liquid chromatographic separation and diode array detection of standard mixtures of the 14 most frequently used synthetic colorants. Protocols for RP-HPLC - " and IP-HPLC techniques have been extensively described and the techniques were compared with micellar electrokinetic capillary chromatography, - which has been shown to be suitable for the analysis of synthetic colorants. 

Tian, K., Qi, S., Cheng, Y., Chen, X., and Hu, Z., Separation and determination of lignans from seeds of Schisandra species by micellar electrokinetic capillary chromatography using ionic liquid as modifier, /. Chromatogr. A, 1078, 181-187, 2005. 

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... 

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... 

Kleiboehmer W, Cammann K, Robert J, et al. 1993. Determination of explosive residues in soils by micellar electrokinetic capillary chromatography and high-performance liquid chromatography. J Chromatogr 638 349-356... 

Enormous advances and growth in the use of ordered media (that is, surfactant normal and reversed micelles, surfactant vesicles, and cyclodextrins) have occurred in the past decade, particularly in their chromatographic applications. New techniques developed in this field include micellar liquid chromatography, micellar-enhanced ultrafiltration, micellar electrokinetic capillary chromatography, and extraction of bioproducts with reversed micelles techniques previously developed include cyclodextrins as stationary and mobile-phase components in chromatography. The symposium upon which this book was based was the first major symposium devoted to this topic and was organized to present the current state of the art in this rapidly expanding field. 

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. 

The phenomena just described are quite similar to what occurs in a liquid partition chromatographic column except that the stationary phase is moving along the length of the column at a much slower rate than the mobile phase. The mechanism of separations is identical in the two cases and depends on differences in distribution constants for analytes between the mobile aqueous phase the hydrocarbon pseudostationary phase. The process is thus true chromatography hence, the name micellar electrokinetic capillary chromatography. Figure 33-15 illustrates two typical separations by MECC. 

Describe a major advantage of micellar electrokinetic capillary chromatography over conventional liquid chromatography. 

Micellar electrokinetic chromatography performed in capillaries is a separation technique combining some of the operational principles of micellar liquid chromatography and capillary zone electrophoresis. This technique was termed micellar electrokinetic capillary chromatography (MECC) by Burton et al. [79]. MECC uses the addition of a surface-active agent in the working electrolyte, which creates new possibilities for electrophetic separations. 

With respect to chromatographic techniques, cationic surfactant micelles have been used as mobile phase additives in the well-known micellar liquid chromatography (MLC) [4]. They have also been employed as pseudostationary phases in micellar electrokinetic capillary chromatography (MEKC) [5]. 

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