Microemulsion Electrokinetic Chromatography MEEKC

Log k appears to correlate with log P for standards between log P —0.5 to 5.0. One limitation of this method is that solutes must be electrically neutral at the pH of the buffer solution because electrophoretic mobility of the charged solute leads to migration times outside the range of Tm and TEof- Basic samples are therefore run at pH 10, and acidic samples at pH 3, thus ensuring that most weak acids and bases will be in their neutral form. This method has been used in a preclinical discovery environment with a throughput of 100 samples per week [24]. 

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Microemulsion electrokinetic chromatography, MEEKC (or MECC), is a relatively new technique which holds some promise of delivering octanol/water partition coefficients much more conveniently than the shake-flask method (Gluck, 1996 Ishihama, 1994). MEEKC is claimed to have all the advantages of an HPLC method but it is not suitable for solutes with pKas much below 7.0 (Adlard, 1995). It has been used over a log P range of -1.0 to +4.0. 

Microemulsion electrokinetic chromatography (MEEKC) or microemulsion electrokinetic capillary chromatography (MEECC) — A special case of - electrokinetic chromatography, where a microemulsion is employed as the dispersed phase. 

Electrokinetic methods capillary electrophoresis (CE), micellar electrokinetic chromatography (MEKC), microemulsion electrokinetic chromatography (MEEKC), capillary electrochromatography (CEC)... 

MICROEMULSION ELECTROKINETIC CHROMATOGRAPHY (MEEKC) FOR NEUTRAL AND/OR CHARGED DRUGS... 

Different types of EKC have been developed. Cy-clodextrins (CDEKC) have been used to form inclusion complexes with solutes to effect their separation. Other examples of EKC include microemulsion electrokinetic chromatography (MEEKC). The MEKC technique (for a detailed treatise, the reader is referred to Ref. 4) utilizes the presence of micelles in the electrolyte buffer solution to influence the migration time of solutes. In this case, the separation carrier is the micelle [5]. 

To date, the use of chemometrics for method development and robustness testing has been published for all areas of CE, including capillary zone electrophoresis (CZE), capillary electrokinetic chromatography (EKC) using chiral selectors for enantioseparations, micellar electrokinetic chromatography (MEKC), and microemulsion electrokinetic chromatography (MEEKC). A comprehensive description can be found in Chapters 5 and 13 as well as in recent reviews (6-11). Several monographs on chemometrics in analytical chemistry have been published such as References 12-14. This chapter will... 

Capillary electrophoresis (CE) is an emerging analytical technique for determination of catechins. The majority of CE studies involve the analysis of catechins in tea infusion, extracts as well as supplements. The three variants of CE suitable for the analysis of catechins include capillary zone electrophoresis (CZE), micellar electro-kinetic chromatography (MEKC), and microemulsion electrokinetic chromatography (MEEKC) with UV detection. In general, the resolution of MEKC was found to be superior to CZE for separation of catechins. MEEKC is a relatively new technique, and the few reports available suggest that it offers a performance similar to MEKC. CE conditions are often quite complex, and many factors, such as buffer composition, pH, presence of surfactants, and column temperature, can all affect the quality of separation and should be optimized individually. On the other hand, CE offers several advantages over HPLC. The short analysis time (<20 minutes), low running costs, and reduced use of solvents make it an attractive alternative for routine analysis of catechins. 

Minimizing the temperature effects discussed above could be obtained with the use of polymer micelles or polymer surfactants [81-83], whose CMC is zero, and even in nonaqueous solvent, the micelle is stable. Although several polymer surfactants are commercially available, no such surfactant is widely accepted, probably because SDS, CTAB, or CTAC, and bile salts are superior to polymer surfactants as the pseudostationary phase in MEKC. Although microemulsion electrokinetic chromatography (MEEKC) is not discussed in this chapter but covered in Chapter 4 by Altria and colleagues, a similar optimization strategy to that in MEKC applies to MEEKC [84-86]. Since... 

As detailed in Chapter 3 by Terabe, micellar electrokinetic chromatography (MEKC) is a useful technique in the retention analysis of water-soluble compounds. The separation and analysis of lypophilic analytes, however, may be difficult in MEKC due to the strong affinity of lypophilic compounds to the micelle resulting in long separation times and poor resolution. An interesting approach for the simultaneous analysis of water- and fat-soluble vitamins by microemulsion electrokinetic chromatography (MEEKC) was proposed by Sanchez. The separation of both water- and fat-soluble vitamins (Bi, B2, B3, Be, B12, C, A palmitate, D, E acetate, and K) was obtained when the microemulsion was prepared with sodium dodecyl sulfate (SDS) as the surfactant, octane as the nonpolar modifier, butanol as the cosurfactant, and propanol as the second cosurfactant. Complete separation of all vitamins was carried out within 55 min however, this approach was tested only in multivitamin formulation. 

Microemulsion electrokinetic chromatography (MEEKC) is an electrophoretic method that can be classified as an extension of micellar electrokinetic chromatography (MEKC) where the micelles are substimted by oil droplets. The high solubilizing ability of MEEKC allows the analysis of highly hydrophobic and aromatic polymer additives, such... 

In this chapter, an overview on the most relevant aspects of the analysis of alkaloids by electromigration methods, namely, capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), micellar electrokinetic chromatography (MEKC), microemulsion electrokinetic chromatography (MEEKC), and capillary electrochromatography (CEC), is given. Selected recent applications of CE in analysis of alkaloids are summarized in a table following the classification according to the chemical nature of the considered compounds. 

Micellar Electrokinetic Chromatography (MEKC) and Microemulsion Electrokinetic Chromatography (MEEKC)... 

Microemulsion electrokinetic chromatography (MEEKC), similarly to MEKC, utilizes as the separation medium a pseudo-stationaiy phase defined as... 

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