Micelles capillary electrophoresis

A form of capillary electrophoresis in which neutral solutes are separated based on their ability to partition into a charged micelle. 

Ornskov, E.,. Gottfries, M. Erickson, S. Folestad. Experimental modelling of drug membrane permeability by capillary electrophoresis using liposomes, micelles and microemulsions./. Pharm. Pharmacol. 2005, 57, 435 2. 

Khaledi, M. G., Micelles as separation media in high-performance liquid chromatography and high-performance capillary electrophoresis overview and perspective, /. Chromatogr. A, 780, 3, 1997. 

Capillary electrophoresis (CE) (see Section 3.5) has been used to determine partition coefficients [320-322]. Lipid vesicles or micelles are added to the buffer whose pH is adjusted to different values. Since drug molecules partition to a different extent as a function of pH, the analysis of mobility vs pH data yields log P values. 

AC ADME ANS AUC BA/BE BBB BBM BBLM BCS BLM BSA CE CHO CMC CPC CPZ CTAB CV DA DOPC DPPC DPPH aminocoumarin absorption, distribution, metabolism, excretion anilinonaphthalenesulfonic acid area under the curve bioavailability-bioequivalence blood-brain barrier brush-border membrane brush-border lipid membrane biopharmaceutics classification system black lipid membrane bovine serum albumin capillary electrophoresis caroboxaldehyde critical micelle concentration centrifugal partition chromatography chlorpromazine cetyltrimethylammonium bromide cyclic votammetry dodecylcarboxylic acid dioleylphosphatidylcholine dipalmitoylphosphatidylcholine diphenylpicrylhydrazyl... 

Anions and uncharged analytes tend to spend more time in the buffered solution and as a result their movement relates to this. While these are useful generalizations, various factors contribute to the migration order of the analytes. These include the anionic or cationic nature of the surfactant, the influence of electroendosmosis, the properties of the buffer, the contributions of electrostatic versus hydrophobic interactions and the electrophoretic mobility of the native analyte. In addition, organic modifiers, e.g. methanol, acetonitrile and tetrahydrofuran are used to enhance separations and these increase the affinity of the more hydrophobic analytes for the liquid rather than the micellar phase. The effect of chirality of the analyte on its interaction with the micelles is utilized to separate enantiomers that either are already present in a sample or have been chemically produced. Such pre-capillary derivatization has been used to produce chiral amino acids for capillary electrophoresis. An alternative approach to chiral separations is the incorporation of additives such as cyclodextrins in the buffer solution. 

Riekkola, M. L., and Wiedmer, S. K. (1997). Potential of capillary electrophoresis with micelles or chiral additives as a purity control method in pharmaceutical industry. Process Control Qual. 10, 169-180. 

KL Rundlett, DW Armstrong. Effect of micelles and mixed micelles on efficiency and selectivity of antibiotic-based capillary electrophoresis enantio-separations. Anal Chem 67 2088—2095, 1995. 

MA Schwarz, K Raith, HH Ruettinger, G Dongowski, RHH Neubert. Investigations of interactions between drugs and mixed bile salt/lecithin micelles—a characterization by micellar affinity capillary electrophoresis. Part III. J Chro-matogr A 781 377-389, 1997. 

MA Schwarz, K Raith, RHH Neubert. Characterization of micelles by capillary electrophoresis. Electrophoresis 19 2145-2150, 1998. 

Y Mrestani, RHH Neubert. Non-ionic micellar affinity capillary electrophoresis for analysis of interactions between micelles and drugs. J Pharm Biomed Anal 24 637-643, 2001. 

Schwarz et al. used ESI-MS detection to characterize the composition of binary (bile salt/phosphatidylcholine) and ternary (bile salt/phophatidy 1-choline/fatty acid) mixed micelles that were used in micellar affinity capillary electrophoresis (43,44). The detrimental effects of the surfactants turned out to be tolerable for short-time qualitative determinations. 

MA Schwarz, K Raith, G Dongowski, R. Neubert. Effect on the partition equilibrium of various drugs by the formation of mixed bile salt/phosphatidylcho-line/fatty acid micelles. A characterization by micellar affinity capillary electrophoresis (MACE). Part IV. J Chromatogr A 809 219-229, 1998. 

Micellar electrokinetic capillary chromatography (MECC), in contrast to capillary electrophoresis (CE) and capillary zone electrophoresis (CZE), is useful for the separation of neutral and partially charged species [266,267]. In MECC, a surfactant, usually sodium dodecyl sulfate (SDS), is added to the buffer solution above its critical micellar concentration to form micelles. Although SDS is certainly the most popular anionic surfactant in MECC, other surfactants such as bile salts have proved to be very effective in separating nonpolar analytes that could not be resolved using SDS [268]. 

In capillary electrophoresis, components of a mixture are separated according to two main factors electrophoretic mobility and electro-osmotic flow. These terms apply to ions, molecules or micelles. 

The separation of phospholipids by micellar electrokinetic capillary electrophoresis (MEKC) has been described (17-19). In this technique, solutes are separated based on their distribution between a mobile (usually aqueous) and a pseudostationary (micellar) phase. Szucs et al. found that the major soybean phospholipids were fully resolved in only 7 minutes using deox ycholic acid for micelle formation in combination with 30% n-propanol at 50°C (18). However, quantification of the separated compounds remains troublesome. This is due first of all to the fact that only UV detection can be used, thus making the response highly dependent on the degree of unsaturation of the phospholipids. Besides, the comparison of peak areas in MEKC is more complicated than in HPLC, because all compounds are moving with different velocities. 

Capillary electrophoresis (CE) provided an orthogonal separation technique. The retention mechanism can be manipulated with buffers or addition of surfactants to form micelles for the analysis where size and charge differences... 

Micellar electrokinetic capillary chromatography (MECC) is a mode of CE similar to CZE, in which surfactants (micelles) are added to the buffer system. Micellar solutions can be used to solubilize hydrophobic compounds that would otherwise be insoluble in water. In MECC the micelles are used to provide a reversed-phase character to the separation mechanism. Although MECC was originally developed for the separation of neutral species by capillary electrophoresis, it has also been shown to enhance resolution in the analysis of a variety of charged species.16... 

Mechref Y, Smith JT, El Rassi Z. Micellar electrokinetic capillary chromatography with in situ charged micelles. VII. Expanding the utility of alkylglycoside-borate micelles to acidic and neutral pH for capillary electrophoresis of dansyl amino acids and herbicides. J Liq Chromatogr 1995 18 3769. 

Riekkola ML, Wiedmar SK, Valko IE, Siren H. Selectivity in capillary electrophoresis in the presence of micelles, chiral selectors and non-aqueous media. / Chromatogr 1997 792A 13—35. 

Since micellar electrokinetic chromatography (MEKC) was hrst introduced in 1984, it has become one of major separation modes in capillary electrophoresis (CE), especially owing to its applicability to the separation of neutral compounds as well as charged ones. Chiral separation is one of the major objectives of CE, as well as MEKC, and a number of successful reports on enantiomer separations by CE and MEKC has been published. In chiral separations by MEKC, the following two modes are normally employed (a) MEKC using chiral micelles and (b) cyclodextrin (CD)-modilied MEKC (CD-MEKC ... 

S. Terabe, Micellar electrokinetic chromatography, in Capillary Electrophoresis Technology (N. A. Guzman, ed.), Marcel Dekker, Inc., New York, 1993, pp. 65-87. J. N. Israelchvilli, in Physics of Amphiphiles Micelles, Vesicles and Microemulsions (V. Degiorgio and M. Corti, eds.). Proceedings of the International School of Physics Enrico Eermi, CourseXC, North-Holland, Amsterdam, 1985, pp. 24-37. 

---