Pharmaceutical analysis MEEKC

Several modes of CE have been described in the literature over past decade [6, 7], The most common are open tubular or capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC), microemulsion elec-trokinetic chromatography (MEEKC), capillary electrochromatograpy (CEC), capillary gel electrophoresis, capillary isoelectric focusing and capillary iso-tachophoresis. Three recent reviews by Watzig [113], Tagliaro etal. [114] and Riekkola etal. [115] summarise the current method development options available to manipulate selectivity. In pharmaceutical analysis, CZE, MEKC, MEEKC and CEC are commonly used. 

Since the first application of CE to pharmaceutical analysis in 1988 [15], the number of reports describing the analysis of numerous different pharmaceutical compounds and formulations by CE has expanded to be in the hundreds. Lunn [13] has covered in detail the CE separation methods for over 700 pharmaceutical compounds taken from hundreds of publications. The objective of this applications section is to provide the reader with an introduction to the main pharmaceutical application areas with examples of successful separations including sources of comprehensive reviews for each area. Within each application area there may be more specialized applications (e.g., chiral MEEKC) for enantiomeric separations and some aspects may be cross-linked with other applications or detection methods to comprehensively cover the topic of this chapter. Sources of extra reading material in the form of review papers will be cited where relevant. 

Broderick M., Donegan S., Power J., Altria K.D., Optimisation of water-in-oil MEEKC in pharmaceutical analysis. J. Pharm. Biomed Anal., 37, 877-884 (2005). 

The method development by MEEKC is useful for the determination of active and excipient compounds as well as related substances of drugs, with very high precision and accuracy. The application of MEEKC in pharmaceutical analysis offers a powerful tool in quality control of pharmaceutical laboratories. 

The reason for this is that if a stable, optically transparent emulsion is to be obtained, the relationship between the amount of the oil phase and the surfactants has to be within a relatively narrow range. Microemulsion elec-trokinetic chromatography has been shown to be a highly applicable technique for the analysis of complex mixtures such as multicomponent formulations and drug-related impurities. This technique opens a new way to determine water-insoluble neutral species such as steroids, which are difficult to analyze by CE. It is therefore likely that the MEEKC method will be increasingly applied for pharmaceutical and biopharmaceutical analyses in coming years. 

MEEKC has become an important field of research in CE offering a large number of appUcations such as estimation of physicochemical properties and for the analysis of different endogenous and exogenous compounds present in different biological and pharmaceutical samples. 

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