Micellar electrokinetic chromatography: A review of methodological and instrumental innovations focusing on practical aspects

Abstract

This review article addresses recent methodological and instrumental innovations in MEKC with emphasis on practical aspects. Like its predecessors, this review is intended to provide an updated overview covering work on the most salient methodological contributions to enhancing sensitivity and resolution in MEKC-based determinations published over the past two years. The most widespread approaches to enhancing sensitivity, which include improving "classical" online sample concentration techniques, combinations of on- and off-line sample concentration protocols and recent developments are discussed, and so are modifications of existing MEKC systems with various micellar phases, the use of BGE additives (organic modifiers, chiral selectors, gold nanoparticles) and coated capillaries, and the implementation of 2D separations and chemometric methods to enhance resolution. Instrumental approaches such as MS and LIF are also discussed, and proposals for overcoming the problems typically encountered in directly coupling MEKC with MS, and the recent inception of quantum dots with a great potential for LIF detection in MEKC, are also dealt with. Finally, foreseeable developments on potential future directions are also expressed.

The successful binomium of multivariate strategies and electrophoresis for the Quality by Design separation of a class of drugs: the case of triptans

“…A good selectivity was obtained by simultaneously adding n-butanol, which can act as cosurfactant, and ethanol, which can widen the electrophoretic window by lowering the EOF. This choice confirmed that solvent-modified MEKC is gaining higher interest with respect to MEEKC due to the higher simplicity of BGE preparation and to the higher stability of micelles with respect to microemulsions [12,32]. In these conditions, the migration order of the peaks was the following: frovatriptan, sumatriptan, rizatriptan, zolmitriptan, almotriptan, naratriptan, indoprofen, and eletriptan.…”

CE‐UV for the characterization of passion fruit juices provenance by amino acids profile with the aid of chemometric tools

“…The improvement obtained with the highest pH and addition of methanol can be explained by the changes in intermolecular interactions that these alterations cause. Lowering the pH affects the localized charge of some analytes and the micelles composition, while addition of methanol alters both the physicochemical properties of the analytes and the micellar medium viscosity and hydrophobicity, besides expanding the migration window by EOF reduction . These conditions alter the solubilities of the amino acids in the micelles, leading to changes in their effective mobilities and thus better resolution .…”

“…Owing to similar electrophoretic mobilities of amino acids, CZE usually does not provide appropriate separation. For this purpose, MEKC using SDS as surfactant has been widely used improving the separation by a partitioning mechanism of the analytes between the BGE and the micelle .…”

Recent advances in capillary electrophoretic migration techniques for pharmaceutical analysis

“…Log P values of drugs have been estimated by MEKC [167][168][169] and MEEKC [102,103] since many years. Furthermore, liposome electrokinetic chromatography employing liposomes as pseudostationary phase has been used for the characterization of liposomal drug formulations as well as drug lipophilicity and drug-liposome interactions [170,171].…”