The Experts below are selected from a list of 1059 Experts worldwide ranked by ideXlab platform
Huwei Liu - One of the best experts on this subject based on the ideXlab platform.
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separation and determination of biphenyl nitrile compounds by Microemulsion Electrokinetic Chromatography with mixed surfactants
Electrophoresis, 2004Co-Authors: Suxuan Gong, Lan Huang, Huwei LiuAbstract:A mixture of six biphenyl nitrile compounds and three related substances with high hydrophobicity and similar structures was successfully separated by Microemulsion Electrokinetic Chromatography (MEEKC) within 30 min. TheMicroemulsion system contained 100 mM sodium dodecyl sulfate (SDS), 80 mM sodium cholate (SC), 0.81% v/v heptane, 7.5% v/v n-butanol, 10% v/v acetonitrile, and 10 mM borate. The addition of SC, organic modifiers, sample preparation, and temperature all showed remarkable effects on the separation. The capacity factor (k) was calculated by using dodecyl benzene as the marker for Microemulsion, and the calculated partition coefficient log P o / w of the solutes was in the range of 3.35-7.38. The log k values matched well with the log P o / w with a correlation coefficient of 0.96. In addition, the linear correlation coefficients of each compound between peak area and concentration were from 0.996 to 0.998 with the repeatability RSD value 586 000. MEEKC was compared with micellar Electrokinetic Chromatography (MEKC) indicating that the former method is more suitable for this separation and can be used for the quality control of biphenyl nitrile compounds in the synthesis of liquid crystals.
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Optimized separation of isoquinoline alkaloids in Thalictrum herbal medicine by Microemulsion Electrokinetic Chromatography
Journal of Liquid Chromatography & Related Technologies, 2003Co-Authors: Yiqi Luo, Suxuan Gong, Huwei LiuAbstract:Abstract Microemulsion Electrokinetic Chromatography (MEEKC), as a promising separation technique providing good selectivity and high efficiency, was used for the separation of seven isoquinoline alkaloids in Thalictrum plant. The optimized separation was studied with regard to pH, the compositions of a Microemulsion system, the additions of organic solvents and sodium cholate (SC), applied voltage, and column temperature. The baseline separation was successfully achieved using the microemusion system at pH 8.0, consisting of 10 mM phosphate, 140 mM sodium dodecyl sulfate (SDS), 100 mM n‐heptane, 12% (v/v) n‐butanol, 1% (v/v) methanol, and 5 mM SC under 25 kV applied voltage and 25°C column temperature within 20 min. Meanwhile, the effects of variables on separation selectivity were discussed.
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Comparison of micellar Electrokinetic Chromatography and Microemulsion Electrokinetic Chromatography for separation of pharmacologically active xanthones from Securidaca inappendiculata
Journal of Separation Science, 2003Co-Authors: Xuedong Yang, Huwei LiuAbstract:Micellar Electrokinetic Chromatography (MEKC) and Microemulsion Electrokinetic Chromatography (MEEKC) have been investigated for the separation of nine xanthones from Securidaca inappendiculata, based on the systematic optimization of such parameters as pH, concentration of borate buffer, and sodium dodecyl sulfate (SDS) concentration. The study indicated that, in MEKC, although the addition of modifiers including organic solvents and cyclodextrins (CDs) could greatly affect the separation selectivity of xanthones, the baseline separation for nine xanthones could not be completed. As a special variant of Electrokinetic Chromatography (EKC), MEEKC successfully achieved the baseline separation of nine xanthones with satisfactory repeatability. Compared with MEKC, MEEKC showed better separation selectivity and higher separation efficiency.
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Separation of Isoquinoline Alkaloids and Saponins by Microemulsion Electrokinetic Chromatography with Anionic and Cationic Surfactants
Chromatographia, 2002Co-Authors: Lei Zhong, Yiqi Luo, Huwei Liu, De An GuoAbstract:Isoquinoline alkaloids and saponins are natural products with significant pharmacological effects. Because of the extreme similarity and diversity of their structures, separation of these compounds by capillary electrophoresis (CE) is difficult. A promising separation technique with good separation selectivity and high efficiency, Microemulsion Electrokinetic Chromatography (MEEKC), has been used to separate ten isoquinoline alkaloids and six saponins fromGleditsia sinensis. Anionic and cationic surfactants such as sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants in MEEKC, on the basis of a series of separation optimizations. For separation of isoquinoline alkaloids comparison of MEEKC with non-aqueous capillary electrophoresis (CE) is discussed with regard to separation efficiency, selectivity, analysis time, and repeatability. Study of the separation of the saponins revealed that separation selectivity was different for MEEKC with CTAB and SDS as surfactants; separation with CTAB was much better than that obtained with SDS.
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Optimized separation of pharmacologically active xanthones from Securidaca inappendiculata by micellar Electrokinetic Chromatography and Microemulsion Electrokinetic Chromatography
Analytica Chimica Acta, 2002Co-Authors: Xuedong Yang, Feng Liu, Lizhen Xiu, Huwei LiuAbstract:Abstract Micellar Electrokinetic Chromatography (MEKC) has been used for the separation of nine xanthones from Securidaca inappendiculata by using sodium dodecyl sulfate (SDS) micellar system, and the effects of different buffer modifiers including sodium cholate (SC), organic solvent and cyclodextrins (CDs) on the separation selectivity have been extensively studied, based on the systematically optimization of such parameters as pH, concentration of running buffer and SDS concentration. The results indicated that the additions of modifiers could greatly affect the separation selectivity of xanthones, and the migration order of those xanthones depends on their structures and solute–micelle-modifier interactions. As a special variant of Electrokinetic Chromatography, Microemulsion Electrokinetic Chromatography (MEEKC) has also been utilized for this separation for the comparison with MEKC, showing that MEEKC has better selectivity.
Hw Liu - One of the best experts on this subject based on the ideXlab platform.
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Separation of biphenyl nitrile compounds by Microemulsion Electrokinetic Chromatography with mixed surfactants
中国化学快报英文版, 2004Co-Authors: Sx Gong, Bo T, Huang L, Hw LiuAbstract:A mixture of nine biphenyl nitrile compounds with high hydrophobicity and similar structures was successfully separated by Microemulsion Electrokinetic Chromatography (MEEKC) within 30 min. The buffer system contained 100 mmol/L sodium dodecyl sulfate (SDS), 80 mmol/L sodium cholate (SC), 0.81% heptane, 7.5% n-butanol, 10% acetonitrile and 10 mmol/L borate. The addition of SC, organic modifiers, sample preparation and temperature all showed remarkable effect on the separation. Meanwhile, the MEEKC method was briefly compared with micellar Electrokinetic Chromatography (MEKC) method.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000223852800017&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, MultidisciplinarySCI(E)中国科技核心期刊(ISTIC)1ARTICLE91063-10661
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Optimized separation of isoquinoline alkaloids in Thalictrum herbal medicine by Microemulsion Electrokinetic Chromatography
journal of liquid chromatography related technologies, 2003Co-Authors: Yq Luo, Bo T, Sx Gong, Li M, Hw LiuAbstract:Microemulsion Electrokinetic Chromatography (MEEKC), as a promising separation technique providing good selectivity and high efficiency, was used for the separation of seven isoquinoline alkaloids in Thalictrum plant. The optimized separation was studied with regard to pH, the compositions of a Microemulsion. system, the additions of organic solvents and sodium cholate (SC), applied voltage,and column temperature. The baseline separation. was successfully achieved using the microemusion system at pH 8.0, consisting of 10 mM phosphate, 140 mM sodium dodecyl sulfate (SDS), 100 mM n-heptane, 12% (v/v) n-butanol, 1% (v/v) methanol, and 5 mM SC under 25 kV applied voltage and 25degreesC column temperature within 20 min. Meanwhile, the effects of variables on separation selectivity were discussed.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000184005600004&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Biochemical Research MethodsChemistry, AnalyticalSCI(E)EI5ARTICLE111719-17302
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Comparison of micellar Electrokinetic Chromatography and Microemulsion Electrokinetic Chromatography for separation of pharmacologically active xanthones from Securidaca inappendiculata
journal of separation science, 2003Co-Authors: Bo T, Xd Yang, Hw LiuAbstract:Micellar Electrokinetic Chromatography (MEKC) and Microemulsion Electrokinetic Chromatography (MEEKC) have been investigated for the separation of nine xanthones from Securidaca inappendiculata, based on the systematic optimization of such parameters as pH, concentration of borate buffer, and sodium dodecyl sulfate (SDS) concentration. The study indicated that, in MEKC, although the addition of modifiers including organic solvents and cyclodextrins (CDs) could greatly affect the separation selectivity of xanthones, the baseline separation for nine xanthones could not be completed. As a special variant of Electrokinetic Chromatography (EKC), MEEKC successfully achieved the baseline separation of nine xanthones with satisfactory repeatability. Compared with MEKC, MEEKC showed better separation selectivity and higher separation efficiency.Chemistry, AnalyticalSCI(E)EI0ARTICLE1-2133-1362
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Optimized separation of nine xanthones by Microemulsion Electrokinetic Chromatography
中国化学快报英文版, 2002Co-Authors: Bo T, Hw LiuAbstract:A Microemulsion Electrokinetic Chromatography method has been firstly used for the separation of the therapeutically important xanthones from Securidaca inappendiculata. The separation of the nine xanthones was systematically optimized with respect to pH, composition of Microemulsion, addition of cyclodextrins, applied voltage and column temperature. Baseline separation was successfully achieved for the nine xanthones, which was also compared with that by micellar Electrokinetic Chromatography.Chemistry, MultidisciplinarySCI(E)中国科技核心期刊(ISTIC)1ARTICLE9877-8801
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Separation of isoquinoline alkaloids and saponins by Microemulsion Electrokinetic Chromatography with anionic and cationic surfactants
chromatographia, 2002Co-Authors: Bo T, Hw Liu, Yq Luo, Li M, Zhong L, Da GuoAbstract:Isoquinoline alkaloids and saponins are natural products with significant pharmacological effects. Because of the extreme similarity and diversity of their structures, separation of these compounds by capillary electrophoresis (CE) is difficult. A promising separation technique with good separation selectivity and high efficiency, Microemulsion Electrokinetic Chromatography (MEEKC), has been used to separate ten isoquinoline alkaloids and six saponins from Gleditsia sinensis. Anionic and cationic surfactants such as sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants in MEEKC, on the basis of a series of separation optimizations. For separation of isoquinoline alkaloids comparison of MEEKC with non-aqueous capillary electrophoresis (CE) is discussed with regard to separation efficiency, selectivity, analysis time, and repeatability Study of the separation of the saponins revealed that separation selectivity was different for MEEKC with CTAB and SDS as surfactants; separation with CTAB was much better than that obtained with SDS.Biochemical Research MethodsChemistry, AnalyticalSCI(E)11ARTICLE11-12709-7165
Kevin D. Altria - One of the best experts on this subject based on the ideXlab platform.
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CAPILLARY ELECTROPHORESIS | Microemulsion Electrokinetic Chromatography
Encyclopedia of Separation Science, 2007Co-Authors: Eamon Mcevoy, Sheila Donegan, Joe Power, Kevin D. AltriaAbstract:Microemulsion Electrokinetic Chromatography (MEEKC) is a mode of capillary electrophoresis (CE), which utilizes Microemulsion as both carrier electrolytes and pseudo-stationary phases within the capillary. The unique solubilizing capability of Microemulsions makes them suitable as sample solvents for a range of charged, neutral, water-insoluble compounds. This article looks at the separation principles of MEEKC, comparison to other forms of CE, method development and optimization parameters and recent applications of MEEKC.
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Determination of folic acid in tablets by Microemulsion Electrokinetic Chromatography.
Journal of Chromatography A, 2004Co-Authors: Maria Segunda Aurora-prado, Claudinei Alves Da Silva, Marina Franco Maggi Tavares, Kevin D. AltriaAbstract:A Microemulsion Electrokinetic Chromatography (MEEKC) method has been developed and validated for the determination of folic acid, a water-soluble vitamin, in a commercial tablet formulation. The analysis was performed using a Microemulsion containing 0.5% (w/w) ethyl acetate, 1.2% (w/w) butan-1-ol, 0.6% (w/w) sodium dodecyl sulfate, 15% (v/v) 2-propanol and 82.7% (w/w) 10 mmol L -1 sodium tetraborate aqueous buffer at pH 9.2. Direct UV detection at 214nm led to an adequate sensitivity without interference from sample excipients. For quantitative purposes, niacin was used as internal standard. Acceptable precision (
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Recent advances in Microemulsion Electrokinetic Chromatography.
Electrophoresis, 2004Co-Authors: Alex Marsh, Sheila Donegan, Joe Power, Brian J. Clark, Margo Broderick, Kevin D. AltriaAbstract:Microemulsion Electrokinetic Chromatography (MEEKC) is an electrodriven separation technique. Separations are typically achieved using oil-in-water Microemulsions, which are composed of nanometre-sized droplets of oil suspended in aqueous buffer. The oil droplets are coated in surfactant molecules and the system is stabilised by the addition of a short-chain alcohol cosurfactant. The novel use of water-in-oil Microemulsions for MEEKC separations has also been investigated recently. This report summarises the different Microemulsion types and compositions used to-date and their applications with a focus on recent papers (2002-2004). The effects of key operating variables (pH, surfactant, cosurfactant, oil phase, buffer, additives, temperature, organic modifier) and methodology techniques are described.
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The use of novel water-in-oil Microemulsions in Microemulsion Electrokinetic Chromatography.
ELECTROPHORESIS, 2004Co-Authors: Kevin D. Altria, Sheila Donegan, Margo Broderick, Joe PowerAbstract:We describe the novel use of water-in-oil (W/O) Microemulsions to achieve unique separations in Microemulsion Electrokinetic Chromatography (MEEKC). The choice and concentration of the buffer type, surfactant and co-surfactant were all examined and optimized. Separations of a range of neutral and acidic analytes was shown to be markedly different to that obtained by (oil-in-water) O/W MEEKC. Neutral solutes are separated by virtue of their solubility (log P) values in O/W MEEKC with the more water-insoluble solutes migrating last. This separation process does not occur in W/O, as neutral solutes are not separated in order of log P.
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Background and operating parameters in Microemulsion Electrokinetic Chromatography.
Electrophoresis, 2003Co-Authors: Kevin D. Altria, P E Mahuzier, Brian J. ClarkAbstract:Microemulsion Electrokinetic Chromatography (MEEKC) is an electrodriven separation technique. Separations are generally achieved using Microemulsions consisting of surfactant-coated nanometer-sized oil droplets suspended in aqueous buffer. A cosurfactant such as a short-chain alcohol is generally used to stabilize the Microemulsion. This review summarizes the various Microemulsion types and compositions that have been used in MEEKC. The effects of key-operating variables such as surfactant type and concentration, cosurfactant type and concentration, buffer pH and type, oil type and concentration, use of organic solvent and cyclodextrin additions, and temperature are described. Specific examples of water-in-oil Microemulsions and chirally selective separations are also covered.
Stig Pedersen-bjergaard - One of the best experts on this subject based on the ideXlab platform.
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Microemulsion Electrokinetic Chromatography – or solvent-modified micellar Electrokinetic Chromatography?
Trends in Analytical Chemistry, 2001Co-Authors: Steen Honoré Hansen, Charlotte Gabel-jensen, Dina T. El-sherbiny, Stig Pedersen-bjergaardAbstract:An overview of the Microemulsion Electrokinetic Chromatography technique and its fields of applications in analytical chemistry are given. The separation mechanisms involved are discussed and the technique is compared to solvent-modified micellar Electrokinetic Chromatography.
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Comparison of Microemulsion Electrokinetic Chromatography and solvent-modified micellar Electrokinetic Chromatography
Journal of Separation Science, 2001Co-Authors: Steen Honoré Hansen, Charlotte Gabel-jensen, Stig Pedersen-bjergaardAbstract:Microemulsion Electrokinetic Chromatography (MEEKC) was investigated with the goal of elucidating the influence exerted by the amount of lipophilic organic phase and the amount of co-surfactant on the migration of a number of neutral test solutes. Furthermore, MEEKC was compared to solvent-modified micellar Electrokinetic Chromatography (MEKC). The organic solvents methanol, ethanol, 1-propanol, 1-butanol, acetonitrile, tetrahydrofuran, and 2-ethoxyethanol serving as co-surfactants in MEEKC were used in similar concentrations in MEKC systems in order to compare the selectivity and separation efficiency of the two kinds of system. The solvent-modified MEKC technique proved to be very similar to MEEKC in performance with respect to both separation selectivity and efficiency of separation.
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Separation of neutral compounds by Microemulsion Electrokinetic Chromatography: fundamental studies on selectivity.
Electrophoresis, 2001Co-Authors: Charlotte Gabel-jensen, Steen Honoré Hansen, Stig Pedersen-bjergaardAbstract:The selectivity of Microemulsion Electrokinetic Chromatography (MEEKC) was studied utilizing some uncharged model compounds like aromatic amides, steroids, and esters of nicotinic acid. The cosurfactant of the Microemulsion was found to be the most important factor affecting the selectivity, and alteration between 6.6% of 1-propanol, 1-butanol, tetrahydrofuran, and 2-ethoxyethanol caused several substantial changes in the migration order. In addition, the nature of the surfactant was found to significantly affect the selectivity. In this case, changes in order of migration was observed by replacement of half the content of sodium dodecyl sulfate (SDS) with either sodium dioctyl sulfosuccinate (SDOSS), 3-(N,N-dimethylmyristylammonio) propanesulfonate (MAPS), polyoxyethylene sorbitan monolaurate (Tween 21), and polyoxyethylene 23 lauryl ether (Brij 35). MEEKC was also accomplished with 3.3% of the anionic surfactant sodium cholate and with the cationic surfactant N-cetyl-N,N,N-trimethylammonium bromide (CTMA). Both provided substantial differences in selectivity as compared to the SDS-based systems. With SDS as surfacant, the concentration was varied within 1.0-4.5%. Minor selectivity changes were observed as the concentration of the surfacant was reduced, but the major effect was a reduction in the total migration time. The organic solvent of the Microemulsion droplets was found only to have minor impact on the selectivity.
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Selectivity in Microemulsion Electrokinetic Chromatography.
Journal of chromatography. A, 2000Co-Authors: Stig Pedersen-bjergaard, Charlotte Gabel-jensen, S Honoré HansenAbstract:Microemulsion Electrokinetic Chromatography (MEEKC) is a most promising separation technique providing good selectivity and high separation efficiency of anionic, cationic as well as neutral solutes. In MEEKC lipophilic organic solvents dispersed as tiny droplets in an aqueous buffer by the use of surfactants provide a pseudo-stationary phase to which the solutes may have an affinity either to the surface or they may even partition into the droplets. When the droplets are charged, typically negatively, they will migrate opposite to the electroosmotic flow and hence separation of neutral solutes may take place. In the present paper focus has been set on how to change selectivity in MEEKC. Changes in the nature of surfactant as well as in pH have been shown to be powerful tools in changing the selectivity. The type of lipophilic organic phase is of less importance for the separation of fairly lipophilic solutes. Also changes in the temperature surrounding the capillary may alter the selectivity.
Steen Honoré Hansen - One of the best experts on this subject based on the ideXlab platform.
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Recent applications of Microemulsion Electrokinetic Chromatography.
ELECTROPHORESIS, 2003Co-Authors: Steen Honoré HansenAbstract:Microemulsions are used in a similar way as micellar solutions are used for separations in capillary electrophoresis. Within the last approximately six years, a number of papers have appeared in the literature in which the separation characteristics of Microemulsion Electrokinetic Chromatography (MEEKC) have been investigated. The total number of papers dealing with MEEKC is now close to 100. One of the major fields of application for MEEKC has been the characterization of the lipophilicity of chemical substances but the technique has also been applied for the analysis of substances within the fields of natural products, pharmaceuticals, vitamins, peptides, proteins, and nucleic acid bases as well as nucleosides. An overview of the applications is given together with the Microemulsions used for each application.
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Microemulsion Electrokinetic Chromatography – or solvent-modified micellar Electrokinetic Chromatography?
Trends in Analytical Chemistry, 2001Co-Authors: Steen Honoré Hansen, Charlotte Gabel-jensen, Dina T. El-sherbiny, Stig Pedersen-bjergaardAbstract:An overview of the Microemulsion Electrokinetic Chromatography technique and its fields of applications in analytical chemistry are given. The separation mechanisms involved are discussed and the technique is compared to solvent-modified micellar Electrokinetic Chromatography.
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Microemulsion Electrokinetic Chromatography or solvent modified micellar Electrokinetic Chromatography
Trends in Analytical Chemistry, 2001Co-Authors: Steen Honoré Hansen, Charlotte Gabeljensen, Dina T Elsherbiny, Stig PedersenbjergaardAbstract:An overview of the Microemulsion Electrokinetic Chromatography technique and its fields of applications in analytical chemistry are given. The separation mechanisms involved are discussed and the technique is compared to solvent-modified micellar Electrokinetic Chromatography.
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Comparison of Microemulsion Electrokinetic Chromatography and solvent-modified micellar Electrokinetic Chromatography
Journal of Separation Science, 2001Co-Authors: Steen Honoré Hansen, Charlotte Gabel-jensen, Stig Pedersen-bjergaardAbstract:Microemulsion Electrokinetic Chromatography (MEEKC) was investigated with the goal of elucidating the influence exerted by the amount of lipophilic organic phase and the amount of co-surfactant on the migration of a number of neutral test solutes. Furthermore, MEEKC was compared to solvent-modified micellar Electrokinetic Chromatography (MEKC). The organic solvents methanol, ethanol, 1-propanol, 1-butanol, acetonitrile, tetrahydrofuran, and 2-ethoxyethanol serving as co-surfactants in MEEKC were used in similar concentrations in MEKC systems in order to compare the selectivity and separation efficiency of the two kinds of system. The solvent-modified MEKC technique proved to be very similar to MEEKC in performance with respect to both separation selectivity and efficiency of separation.
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Separation of neutral compounds by Microemulsion Electrokinetic Chromatography: fundamental studies on selectivity.
Electrophoresis, 2001Co-Authors: Charlotte Gabel-jensen, Steen Honoré Hansen, Stig Pedersen-bjergaardAbstract:The selectivity of Microemulsion Electrokinetic Chromatography (MEEKC) was studied utilizing some uncharged model compounds like aromatic amides, steroids, and esters of nicotinic acid. The cosurfactant of the Microemulsion was found to be the most important factor affecting the selectivity, and alteration between 6.6% of 1-propanol, 1-butanol, tetrahydrofuran, and 2-ethoxyethanol caused several substantial changes in the migration order. In addition, the nature of the surfactant was found to significantly affect the selectivity. In this case, changes in order of migration was observed by replacement of half the content of sodium dodecyl sulfate (SDS) with either sodium dioctyl sulfosuccinate (SDOSS), 3-(N,N-dimethylmyristylammonio) propanesulfonate (MAPS), polyoxyethylene sorbitan monolaurate (Tween 21), and polyoxyethylene 23 lauryl ether (Brij 35). MEEKC was also accomplished with 3.3% of the anionic surfactant sodium cholate and with the cationic surfactant N-cetyl-N,N,N-trimethylammonium bromide (CTMA). Both provided substantial differences in selectivity as compared to the SDS-based systems. With SDS as surfacant, the concentration was varied within 1.0-4.5%. Minor selectivity changes were observed as the concentration of the surfacant was reduced, but the major effect was a reduction in the total migration time. The organic solvent of the Microemulsion droplets was found only to have minor impact on the selectivity.