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Shigeru Terabe - One of the best experts on this subject based on the ideXlab platform.
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Twenty-five years of Micellar Electrokinetic Chromatography
Procedia Chemistry, 2010Co-Authors: Shigeru TerabeAbstract:Abstract Micellar Electrokinetic Chromatography (MEKC), which can separate neutral analytes as well as charged analytes by the capillary electrophoretic technique, was developed in 1982 and the first paper was published in 1984. The authors’ group concentrated their effort into the characterization of MEKC as a separation technique until early 1990s. Most issues in MEKC separations were successfully solved and wide applicability of MEKC was verified in 1990s. In particular, sweeping, an on-line sample preconcentration technique, was very successful for the concentration of neutral analyte as well as ionic ones. In this paper, our studies on MEKC will be summarized from the personal viewpoint of the author.
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capillary separation Micellar Electrokinetic Chromatography
Reviews in Analytical Chemistry, 2009Co-Authors: Shigeru TerabeAbstract:Micellar Electrokinetic Chromatography (MEKC), a separation mode of capillary electrophoresis (CE), has enabled the separation of electrically neutral analytes. MEKC can be performed by adding an ionic micelle to the running solution of CE without modifying the instrument. Its separation principle is based on the differential migration of the ionic micelles and the bulk running buffer under electrophoresis conditions and on the interaction between the analyte and the micelle. Hence, MEKC's separation principle is similar to that of Chromatography. MEKC is a useful technique particularly for the separation of small molecules, both neutral and charged, and yields high-efficiency separation in a short time with minimum amounts of sample and reagents. To improve the concentration sensitivity of detection, several on-line sample preconcentration techniques such as sweeping have been developed.
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anion selective exhaustive injection sweep Micellar Electrokinetic Chromatography
Journal of Chromatography A, 2001Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:Abstract A selective on-line sample concentration technique of anion selective exhaustive injection (ASEI)-sweep–Micellar Electrokinetic Chromatography (MEKC) was evaluated using a cationic surfactant. To suppress the electroosmotic flow, a polyacrylamide-coated capillary was introduced. Some aromatic carboxylic acids, dansyl amino acids, and naphthalenedisulfonic acids were used as test analytes. About 1000- to 6000-fold increases in detection sensitivity were obtained in terms of peak heights by ASEI-sweep–MEKC.
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enantiomer separation of drugs by Micellar Electrokinetic Chromatography using chiral surfactants
Journal of Chromatography A, 2000Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:Abstract A review surveying enantiomer separations by Micellar Electrokinetic Chromatography (MEKC) using chiral surfactants is described. MEKC is one of the most popular techniques in capillary electrophoresis, where neutral compounds can be analyzed as well as charged ones, and the use of chiral micelles enable one to achieve the enantioseparation. The chiral MEKC systems are briefly reviewed according to the types of chiral surfactants along with typical applications. As chiral micelles or pseudostationary phases in MEKC, various natural and synthetic chiral surfactants are used, including several low-molecular-mass surfactants and polymerized surfactants or high-molecular-mass surfactants. Cyclodextrin modified MEKC using chiral micelles is also considered.
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Micellar Electrokinetic Chromatography
Bulletin of the Chemical Society of Japan, 1998Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:A review of the research on Micellar Electrokinetic Chromatography (MEKC), carried out mainly in our laboratory, is described from the viewpoints of (1) fundamental characteristics of MEKC, such as the separation principle, chromatographic parameters, selectivity and resolution, thermodynamic parameters, retention index, and band broadening; (2) selectivity manipulation, including effects of surfactants, temperature, pH, and various additives; (3) on-line coupling of MEKC with mass spectrometry; (4) applications, such as the separation of closely related compounds and enantiomer separations; and (5) on-line neutral sample concentration techniques.
Koji Otsuka - One of the best experts on this subject based on the ideXlab platform.
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anion selective exhaustive injection sweep Micellar Electrokinetic Chromatography
Journal of Chromatography A, 2001Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:Abstract A selective on-line sample concentration technique of anion selective exhaustive injection (ASEI)-sweep–Micellar Electrokinetic Chromatography (MEKC) was evaluated using a cationic surfactant. To suppress the electroosmotic flow, a polyacrylamide-coated capillary was introduced. Some aromatic carboxylic acids, dansyl amino acids, and naphthalenedisulfonic acids were used as test analytes. About 1000- to 6000-fold increases in detection sensitivity were obtained in terms of peak heights by ASEI-sweep–MEKC.
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enantiomer separation of drugs by Micellar Electrokinetic Chromatography using chiral surfactants
Journal of Chromatography A, 2000Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:Abstract A review surveying enantiomer separations by Micellar Electrokinetic Chromatography (MEKC) using chiral surfactants is described. MEKC is one of the most popular techniques in capillary electrophoresis, where neutral compounds can be analyzed as well as charged ones, and the use of chiral micelles enable one to achieve the enantioseparation. The chiral MEKC systems are briefly reviewed according to the types of chiral surfactants along with typical applications. As chiral micelles or pseudostationary phases in MEKC, various natural and synthetic chiral surfactants are used, including several low-molecular-mass surfactants and polymerized surfactants or high-molecular-mass surfactants. Cyclodextrin modified MEKC using chiral micelles is also considered.
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Micellar Electrokinetic Chromatography
Bulletin of the Chemical Society of Japan, 1998Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:A review of the research on Micellar Electrokinetic Chromatography (MEKC), carried out mainly in our laboratory, is described from the viewpoints of (1) fundamental characteristics of MEKC, such as the separation principle, chromatographic parameters, selectivity and resolution, thermodynamic parameters, retention index, and band broadening; (2) selectivity manipulation, including effects of surfactants, temperature, pH, and various additives; (3) on-line coupling of MEKC with mass spectrometry; (4) applications, such as the separation of closely related compounds and enantiomer separations; and (5) on-line neutral sample concentration techniques.
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Micelles as pseudo-stationary phases in Micellar Electrokinetic Chromatography.
Journal of Chromatography A, 1997Co-Authors: Pim G. Muijselaar, Koji Otsuka, Shigeru TerabeAbstract:This review article describes some general comments on Micellar Electrokinetic Chromatography (MEKC) from the viewpoint of pseudo-stationary phases and presents a compiled list of surfactants used for MEKC, prepared from published papers. We tried to give comments on some typical surfactants from the practical point of view.
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Enantiomeric separation by Micellar Electrokinetic Chromatography
Trends in Analytical Chemistry, 1993Co-Authors: Koji Otsuka, Shigeru TerabeAbstract:Abstract Enantiomeric separation by Micellar Electrokinetic Chromatography (MEKC) has been developed recently by using chiral surfactants or a cyclodextrin (CD) modified system (CD-MEKC). As chiral detergents, some amino acid derivatives, bile salts, glycosides and saponins are used with or without achiral micelles and other additives. In CD-MEKC, β- or γ-CDs and sodium dodecyl sulphate are normally used.
Zhide Hu - One of the best experts on this subject based on the ideXlab platform.
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Separation of diastereoisomers of podophyllum lignans by Micellar Electrokinetic Chromatography
Journal of Chromatography A, 2002Co-Authors: Xuan Tian, Xingguo Chen, Zhide HuAbstract:Abstract Seven pairs of diastereoisomers of podophyllum lignans at 2-position, including two pairs of spin-labeled compounds, were separated by Micellar Electrokinetic Chromatography with 5 m M sodium tetraborate–20 m M NaH 2 PO 4 –120 m M sodium dodecylsulfate–30% (v/v) 2-propanol (pH 6.5–7) within 35 min. The migration behaviors of the compounds with different types and concentrations of organic modifiers were studied. The method can be used to identify the purification of the lignans, monitor the 2-H configuration transformation, and determine the 2-H configuration of the spin-labeled derivatives.
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Separation and determination of podophyllum lignans by Micellar Electrokinetic Chromatography
Journal of Chromatography A, 2001Co-Authors: Xuan Tian, Xingguo Chen, Zhide HuAbstract:A Micellar Electrokinetic Chromatography method was established for the quantitative analysis of seven podophyllum lignans in Podophyllum emodi Wall. var. chinesis sprague. The optimum buffer system was 10 mM NaH2PO4–5 mM borate–100 mM sodium dodecylsulfate–30% isopropanol (pH 7.20). Voltage was 18 kV and detection at 214 nm. The second derivative chromatogram was used to determine a low-content component and those not fully separated from adjacent ones. The RSD values of migration times and peak areas were
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separation and determination of podophyllum lignans by Micellar Electrokinetic Chromatography
Journal of Chromatography A, 2001Co-Authors: Xuan Tian, Xingguo Chen, Zhide HuAbstract:A Micellar Electrokinetic Chromatography method was established for the quantitative analysis of seven podophyllum lignans in Podophyllum emodi Wall. var. chinesis sprague. The optimum buffer system was 10 mM NaH2PO4–5 mM borate–100 mM sodium dodecylsulfate–30% isopropanol (pH 7.20). Voltage was 18 kV and detection at 214 nm. The second derivative chromatogram was used to determine a low-content component and those not fully separated from adjacent ones. The RSD values of migration times and peak areas were <2.2 and <5.5%, respectively. The effects of several CE parameters on the resolutions were studied systematically.
Yasushi Ishihama - One of the best experts on this subject based on the ideXlab platform.
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cyclodextrin modified Micellar Electrokinetic Chromatography separation of hydrophobic and enantiomeric compounds
Journal of Chromatography A, 1993Co-Authors: Shigeru Terabe, Yasushi Ishihama, Yosuke Miyashita, Osamu ShibataAbstract:Abstract Cyclodextrin (CD)-modified Micellar Electrokinetic Chromatography was applied to the separation of closely related aromatic compounds and enantiomeric separations using CD together with sodium dodecyl sulphate (SDS). Nine isomeric dimethylnaphthalenes, which were not resolved at all with an SDS solution, were successfully separated with γ-CD and SDS. Sixteen polycyclic aromatic hydrocarbons were also almost completely separated. Dansylated (DnS)- dl -amino acids were optically resolved with combinations of SDS and β- or γ-CD and sodium taurodeoxycholate and γ-CD. Maltoheptaose was employed instead of CD, giving partial resolution of some DnS- dl -amino acids.
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Enantiomeric separation by Micellar Electrokinetic Chromatography using saponins
Journal of Liquid Chromatography & Related Technologies, 1993Co-Authors: Yasushi Ishihama, Shigeru TerabeAbstract:Abstract Glycyrrhizic acid (GRA) and β-escin were employed in Micellar Electrokinetic Chromatography (MEKC) for enantiomeric separation. Both GRA and β-escin are saponins and natural chiral surfactants. A mixed micelle consisting of GRA, octyl-β-D-glucoside, and sodium dodecyl sulfate (SDS) was successfully used for enantiomeric separation of dansy-lated DL-amino acids. β-Escin was also employed to prepare a mixed micelle with SDS and the mixed micelle was capable of separating phe-nylthiohydantoin-DL-amino acids under acidic conditions.
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microemulsion Electrokinetic Chromatography comparison with Micellar Electrokinetic Chromatography
Journal of Chromatography A, 1992Co-Authors: Shigeru Terabe, Yasushi Ishihama, Norio Matsubara, Yukihiro OkadaAbstract:Abstract The fundamental characteristics of microemulsion Electrokinetic Chromatography (MEEKC) were studied in comparison with Micellar Electrokinetic Chromatography (MEKC). A microemulsion consisting of heptane-sodium dodecyl sulphate-butanol-buffer (pH 7.0) (0.81:1.66:6.61:90.92) was mainly employed. The separation selectivity of MEEKC was compared with that of MEKC with SDS micelles by using three different test mixtures. The microemulsion showed a stronger affinity to non-polar compounds than the SDS micelle. The migration-time window in MEEKC was easily extended owing to an increase in the electrophoretic mobility of the microemulsion by increasing the SDS fraction in the microemulsion. The efficiency in MEEKC was also compared with that in MEKC. The plate heights in MEEKC were higher than, but less than double, those in MEKC. The effect of microheterogeneity was not significant but the effect of sorption-desorption kinetics seemed more serious in MEEKC than in MEKC.
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effect of urea addition in Micellar Electrokinetic Chromatography
Journal of Chromatography A, 1991Co-Authors: Shigeru Terabe, Hiroyuki Nishi, Yasushi Ishihama, Tsukasa Fukuyama, Koji OtsukaAbstract:Abstract The addition of urea to a Micellar solution was developed for the separation of hydrophobic compounds by Micellar Electrokinetic Chromatography (MEKC). The logarithm of the capacity factor (k') decreased linearly with increasing concentration of urea. The use of a high concentration of urea allowed the MEKC separation of hydrophobic compounds, which were mostly included in the micelle and could not be resolved by conventional MEKC. The addition of urea also expanded the migration-time window and hence enhanced the resolution. The effect of urea is discussed from the standpoint of the contribution of urea to a diminished water structure around a hydrophobic solute. Two succesful examples of the application of the technique are given for the MEKC separation of a complex mixture and hydrophobic compounds.
Joselito P. Quirino - One of the best experts on this subject based on the ideXlab platform.
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Sweeping of neutral analytes in partial-filling Micellar Electrokinetic Chromatography with electrospray ionization mass spectrometry.
Electrophoresis, 2011Co-Authors: Joselito P. QuirinoAbstract:Sweeping improved the peak intensity of neutral analytes (i.e. dialkylphthalates) more than 100-fold without compromise to separation efficiency in partial-filling Micellar Electrokinetic Chromatography with electrospray ionization mass spectrometry detection.
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exceeding 5000 fold concentration of dilute analytes in Micellar Electrokinetic Chromatography
Science, 1998Co-Authors: Joselito P. Quirino, Shigeru TerabeAbstract:When a neutral analyte zone is injected into a charged pseudostationary phase, the length of the zone is predicted to be narrowed by 1/(1 + k), where k is the retention factor. The conditions for zone narrowing to occur assume negligible electroosmotic flow, a relatively constant electric field along the capillary column, and no pseudostationary phase in the injected analyte mixture. The theoretically expected concentration enhancement was demonstrated experimentally. Consequently, the detection sensitivity of analytes in Micellar Electrokinetic Chromatography (MEKC) can be improved significantly. For example, 9 to 18 parts per billion of an environmentally important racemic herbicide spiked in lake water was separated by MEKC and detected by ultraviolet absorption.
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on line concentration of neutral analytes for Micellar Electrokinetic Chromatography ii reversed electrode polarity stacking mode
Journal of Chromatography A, 1998Co-Authors: Joselito P. Quirino, Shigeru TerabeAbstract:Basic conditions for the on-line neutral sample concentration by reversed electrode polarity stacking mode for Micellar Electrokinetic Chromatography are developed theoretically and experimentally verified. Stacking is mainly dependent on analyte retention factors and nature of the pseudostationary phases. More than an order of magnitude improvement in concentration detection limit is achieved for resorcinol using high molecular mass surfactants.
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On-line concentration of neutral analytes for Micellar Electrokinetic Chromatography
Journal of Chromatography A, 1997Co-Authors: Joselito P. Quirino, Shigeru TerabeAbstract:Basic conditions for the on-line neutral sample concentration by reversed electrode polarity stacking mode for Micellar Electrokinetic Chromatography are developed theoretically and experimentally verified. Stacking is mainly dependent on analyte retention factors and nature of the pseudostationary phases. More than an order of magnitude improvement in concentration detection limit is achieved for resorcinol using high molecular mass surfactants
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Stacking of neutral analytes in Micellar Electrokinetic Chromatography.
Journal of Capillary Electrophoresis, 1997Co-Authors: Joselito P. Quirino, Shigeru TerabeAbstract:: On-line concentration techniques for neutral analytes by sample stacking in Micellar Electrokinetic Chromatography are reviewed. Discussions regarding the fundamentals and practical applications are conveyed. A high gain in sensitivity of 10- to more than 100-fold using normal capillary cell dimension is provided without crucial loss of resolution by the techniques. More than 1000-fold gain in sensitivity (lowering limits of detection to the nM range) is obtained together with an extended pathlength cell.
