Micellar electrokinetic chromatography: A practical overview of current methodological and instrumental advances

Silva, Manuel

doi:10.1002/elps.201000344

Cited by 36 publications

(24 citation statements)

References 151 publications

(247 reference statements)

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“…MEKC grew to a similar extent as regards methodological and instrumental advances in its implementation in routine analysis laboratories over the reviewed period (2010 and 2011) as in previous ones ; however, some emergent topics included in previous reviews have failed to fully meet their initial expectations. Thus, the use of carbon nanostructures and ionic liquids as alternative pseudostationary phases (PSPs) for SDS has not progressed as expected, and no new uses of in‐capillary derivatization have been reported.…”

Section: Introductionmentioning

confidence: 94%

“…The key problem in constructing a 2D CE separation system lies in designing a reliable interface to switch the effluents from the first dimension to the second. As in previous reviews , Dovichi's group continues to be the most salient reference in this field; in recent years, however, Zhang and Zhang have introduced a remarkable innovation involving the incorporation of a sample concentration step between the two dimensions to avoid sample zone diffusion at the interface. Thus, the electroaccumulation focusing method was used at the junction between the two capillaries to avoid diffusion of the primarily preconcentrated and separated analyte bands at the interface.…”

Section: Approaches To Improving Resolutionmentioning

confidence: 99%

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

Silva

2012

Electrophoresis

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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.

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Section: Introductionmentioning

confidence: 94%

Section: Approaches To Improving Resolutionmentioning

confidence: 99%

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

Silva

2012

Electrophoresis

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“…In MCE analysis, SDS is the most commonly used PSP because of its high stability, low Krafft point and high solubilizing power. 4 …”

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confidence: 99%

Electrophoretic Extraction of Low Molecular Weight Cationic Analytes from Sodium Dodecyl Sulfate Containing Sample Matrices for Their Direct Electrospray Ionization Mass Spectrometry

2015

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While the use of sodium dodecyl sulfate (SDS) in separation buffers allows efficient analysis of complex mixtures, its presence in the sample matrix is known to severely interfere with the mass-spectrometric characterization of analyte molecules. In this article, we report a microfluidic device that addresses this analytical challenge by enabling inline electrospray ionization mass spectrometry (ESI-MS) of low molecular weight cationic samples prepared in SDS containing matrices. The functionality of this device relies on the continuous extraction of analyte molecules into an SDS-free solvent stream based on the free-flow zone electrophoresis (FFZE) technique prior to their ESI-MS analysis. The reported extraction was accomplished in our current work in a glass channel with microelectrodes fabricated along its sidewalls to realize the desired electric field. Our experiments show that a key challenge to successfully operating such a device is to suppress the electroosmotically driven fluid circulations generated in its extraction channel that otherwise tend to vigorously mix the liquid streams flowing through this duct. A new coating medium, N-(2-triethoxysilylpropyl) formamide, recently demonstrated by our laboratory to nearly eliminate electroosmotic flow in glass microchannels was employed to address this issue. Applying this surface modifier, we were able to efficiently extract two different peptides, human angiotensin I and MRFA, individually from an SDS containing matrix using the FFZE method and detect them at concentrations down to 3.7 and 6.3 µg/mL, respectively, in samples containing as much as 10 mM SDS. Notice that in addition to greatly reducing the amount of SDS entering the MS instrument, the reported approach allows rapid solvent exchange for facilitating efficient analyte ionization desired in ESI-MS analysis.

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“…However, SDS micelles in MEKC often show insufficient selectivity for highly hydrophobic compounds as all analytes tend to be partitioned into micelles and migrate with the same velocity [1,2]. Many alternative approaches for improving resolution in MEKC have been developed in recent years [3][4][5][6], the most popular and effective being the use of additives. This approach works by altering the apparent distribution constant between micelles and the surrounding medium or the velocity ratio of the two phases [1].…”

Section: Introductionmentioning

confidence: 99%

Separation of Fluoroquinolones by MEKC Modified with Hydrophobic Ionic Liquid as a Modifier

et al. 2011

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The hydrophobic ionic liquid [BMIM]PF 6 (1-butyl-3-methylimidazolium hexafluorophosphate) can interact with sodium dodecyl sulfate (SDS) micelles in aqueous solution and modify their physicochemical properties to produce a unique separation efficiency in micellar electrokinetic chromatography (MEKC). An MEKC method was developed using [BMIM]PF 6 as a modifier for separating eight fluoroquinolone compounds (ciprofloxacin, enrofloxacin, gatifloxacin, ofloxacin, norfloxacin, enoxacin, pazufloxacin, and tosufloxacin). The effects of several parameters on the separation selectivity, e.g., pH, concentration of background electrolyte, concentration ratio and amount of [BMIM]PF 6 and SDS, were investigated. Under the optimal conditions of 10 mmol L -1 sodium borate, pH 7.1, 1.7% (w/w) SDS, 1.5% (w/w) [BMIM]PF 6 with 18 kV as running voltage, the eight investigated quinolone compounds were baseline separated within 15 min. The selectivity of the developed method differed from that of the simple SDS micelles system containing no ionic liquid. The results suggest that hydrophobic ionic liquids should be promising modifiers in capillary electrophoresis, especially in MEKC analysis.

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Micellar electrokinetic chromatography: A practical overview of current methodological and instrumental advances

Cited by 36 publications

References 151 publications

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

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

Electrophoretic Extraction of Low Molecular Weight Cationic Analytes from Sodium Dodecyl Sulfate Containing Sample Matrices for Their Direct Electrospray Ionization Mass Spectrometry

Separation of Fluoroquinolones by MEKC Modified with Hydrophobic Ionic Liquid as a Modifier

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