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Zheng Y, Wang X, Ji Y. Monoliths with proteins as chiral selectors for enantiomer separation. Talanta 2012; 91:7-17. [DOI: 10.1016/j.talanta.2012.01.039] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 01/15/2012] [Accepted: 01/18/2012] [Indexed: 12/25/2022]
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2
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Yang Y, Geng X. Mixed-mode chromatography and its applications to biopolymers. J Chromatogr A 2011; 1218:8813-25. [DOI: 10.1016/j.chroma.2011.10.009] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 10/06/2011] [Accepted: 10/06/2011] [Indexed: 10/16/2022]
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3
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Mangelings D, Vander Heyden Y. Enantioselective capillary electrochromatography: recent developments and new trends. Electrophoresis 2011; 32:2583-601. [PMID: 21910129 DOI: 10.1002/elps.201100009] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 03/10/2011] [Accepted: 03/10/2011] [Indexed: 11/11/2022]
Abstract
Since its development in the early 1970s, CEC has been studied quite extensively, but unfortunately its use is still mostly located at an academic level. Reasons for this are the limited availability of commercially available stationary phases (SPs) and columns, along with some practical limitations, such as column fragility, lack of column robustness and reproducibility. Nevertheless, CEC maintains a place among the separation techniques, probably because of its unique feature to combine two separation principles. Also in the field of chiral separations, CEC is often used as a separation technique and already showed its potential for this kind of analyses. This overview will focus on the recent applications, i.e. between 2006 and 2010, in enantioselective analysis by means of CEC. For the selected applications, the used SPs (chiral selectors) and their potential for future method development or screening purposes will be evaluated and critically discussed.
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Affiliation(s)
- Debby Mangelings
- Department of Analytical Chemistry and Pharmaceutical Technology, Center for Pharmaceutical Research, Vrije Universiteit Brussel, Brussels, Belgium.
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4
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Guan X, Yan G, Gao M, Hong G, Deng C, Zhang X. Intact-protein trapping columns for proteomic analysis in capillary high-performance liquid chromatography. J Chromatogr A 2010; 1217:6875-81. [PMID: 20870240 DOI: 10.1016/j.chroma.2010.08.051] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 06/21/2010] [Accepted: 08/20/2010] [Indexed: 11/17/2022]
Abstract
A new type of monolithic trapping columns with high mechanical strength was prepared by thin-layer sol-gel coating method and applied to trapping intact proteins for on-line capillary liquid chromatography. Monolithic trapping columns were fabricated by entrapping C8 reversed-phase particles into the capillary columns through a sol-gel network, which was formed by hydrolysis and polycondensation of methyltriethoxysilane. Hundreds times of trapping/untrapping for intact proteins were carried out. The trapping columns showed long-term stability up to 300 bar. Recovery, loading capacity and reproducibility of trapping columns were evaluated using four proteins. The recovery of four protein mixtures for the C8 monolithic trapping columns was 99.3% on average. The loading capacity of 5 mm × 320 μm i.d. C8 trapping columns for the protein mixtures was 30 μg. Day-to-day relative standard deviation (RSD) values for recoveries of protein mixtures on the same C8 trapping column ranged from 2.34 to 5.87%, column-to-column RSD values were from 3.01 to 6.81%. The C8 trapping columns were used to trap normal mouse liver intact proteins in a capillary liquid chromatography system. Results demonstrated high efficiency of the monolithic trapping columns for trapping intact proteins for proteomic analysis in on-line capillary liquid chromatography system.
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Affiliation(s)
- Xia Guan
- Department of Chemistry, Fudan University, Shanghai 200433, China
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5
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Svec F. CEC: selected developments that caught my eye since the year 2000. Electrophoresis 2009; 30 Suppl 1:S68-82. [PMID: 19517503 DOI: 10.1002/elps.200900062] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
During the last decade, a number of new developments have emerged in the field of CEC. This paper focuses only on monolithic columns prepared from synthetic polymers. Monolithic columns have become a well-established format of stationary phases for CEC immediately after their inception in the mid-1990s. They are readily prepared in situ from liquid precursors. Also, the control over both porous properties and surface chemistries is easy to achieve. These advantages make the monolithic separation media an attractive alternative to capillary columns packed with particulate materials. Since the number of papers concerned with just this single topic of polymer-based monolithic CEC columns is large, this overview describes only those approaches this author found interesting.
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Affiliation(s)
- Frantisek Svec
- The Molecular Foundry, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA 94720-8197, USA.
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6
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Huang G, Zeng W, Lian Q, Xie Z. Pressurized CEC of neutral and charged solutes using silica monolithic stationary phases functionalized with 3-(2-aminoethylamino)propyl ligands. J Sep Sci 2008; 31:2244-51. [PMID: 18563758 DOI: 10.1002/jssc.200800009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A novel silica monolithic stationary phase functionalized with 3-(2-aminoethylamino)propyl ligands for pressurized CEC has been presented. The monolithic capillary columns were prepared by a sol-gel process in 75 microm id fused-silica capillaries and followed by a chemical modification. The diamino groups on the surface of the stationary phase are meant to generate the chromatographic surface and a substantial anodic EOF as well as to provide electrostatic interaction sites for charged solutes. The electrochromatographic characterization and column performance were evaluated by a variety of neutral and charged solutes. It was observed that the anodic EOF for the diamine-bonded monolith was greatly affected by the reaction time with 3-(2-aminoethylamino)propyltrimethoxysilane and the PEG amount in the sol-gel reaction mixture in addition to the mobile phase conditions. The monolithic stationary phase exhibited hydrophilic interaction chromatographic behavior toward neutral solutes. Good separations of various solutes including phenols, nucleic acid bases, nucleosides and nucleotides were achieved under different experimental conditions. Fast and efficient separations were obtained with high plate counts reaching more than 130,000 plates/m.
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Affiliation(s)
- Guihua Huang
- Department of Chemistry, Fuzhou University, Fuzhou, China
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7
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Wu R, Hu L, Wang F, Ye M, Zou H. Recent development of monolithic stationary phases with emphasis on microscale chromatographic separation. J Chromatogr A 2008; 1184:369-92. [DOI: 10.1016/j.chroma.2007.09.022] [Citation(s) in RCA: 232] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Revised: 09/06/2007] [Accepted: 09/11/2007] [Indexed: 12/28/2022]
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8
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Wang J, Lü H, Lin X, Xie Z. Monolithic column with double mixed-modes of hydrophilic interaction/ cation-exchange and reverse-phase/ cation-exchange stationary phase for pressurized capillary electrochromatography. Electrophoresis 2008; 29:928-35. [DOI: 10.1002/elps.200700600] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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9
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Oguri S, Oga C, Takeda H. Micro-magnetic particles frit for capillary electrochromatography. J Chromatogr A 2007; 1157:304-8. [PMID: 17481646 DOI: 10.1016/j.chroma.2007.04.043] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 04/04/2007] [Accepted: 04/12/2007] [Indexed: 11/18/2022]
Abstract
This paper presents a new method for making frit using soft-ferrite-based micro-magnetic particles (MMPs) in a micro-space, such as in a capillary tube. The MMPs-frit was made by injecting an aliquot of 10 microm (outer diameter; o.d.)-MMPs-suspension in methanol (ca. 1mg/ml) into a capillary tube (75 microm inner diameter (i.d.) x 375 microm o.d. x ca. 35 cm length) that was already sandwiched between a pair of cylindrical Neodium (Nd-Fe-B) magnets (1.5 mm o.d. x 1.5 mm height, 280 mT) at a position where the frit was made. The MMPs were trapped in the capillary tube as a frit due to the attraction of the magnets placed at surface on the capillary tube. With regard to durability, the frit was stable for methanol flow with a flow rate of 400 microl/min at room temperature. Using such a frit, a capillary column (20 cm long) was prepared by injecting a 5 microm (o.d.)-ODS-particle suspension in methanol (ca. 0.4 mg/microl) into the capillary tube. The MMPs-frits-ODS-packed column was stable for methanol for a flow pressure less than 20MPa. When comparing the present column with a conventional sintered-frits-ODS-packed column for the purposes of separating five kinds of biogenic amines by means of an on-column derivatization capillary electrochromatography (CEC), the performance of the MMPs-frits capillary column was almost equivalent to that of the sintered-frits-ODS-packed column.
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Affiliation(s)
- Shigeyuki Oguri
- Laboratory of Food Science, Department of Home Economics, Aichi-Gakusen University, 28 Kamikawanari, Hegoshi-cho, Okazaki City 444-8520, Japan.
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Xie R, Oleschuk R. Photoinduced polymerization for entrapping of octadecylsilane microsphere columns for capillary electrochromatography. Anal Chem 2007; 79:1529-35. [PMID: 17297951 DOI: 10.1021/ac061349t] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel fritless capillary column for capillary electrochromatography (CEC) has been developed. The ODS microspheres were packed into a capillary and were then immobilized within an organic polymer prepared in situ through a photopolymerization process. The entrapment conditions were investigated to minimize the effect of the polymer matrix on the chromatographic properties of the packing material. The organic polymer matrix in the microsphere-packed column functions to link microspheres at specific sphere-sphere and sphere-capillary contact points. CEC separations of a PAH test mixture using entrapped columns with different UV illumination times were compared in terms of retention factor and separation efficiency. The optimized entrapped column demonstrated better chromatographic performance than similarly packed columns with conventional inlet and outlet frits. The electrochromatographic separations of hormones and peptides were also demonstrated on entrapped ODS columns.
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Affiliation(s)
- Ruixi Xie
- Department of Chemistry, Queen's University, Kingston, Ontario, Canada, K7L 3N6
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11
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Debowski JK. SELECTED APPLICATIONS OF CAPILLARY ELECTROCHROMATOGRAPHY IN THE PHARMACEUTICAL INDUSTRY: TO BUY OR NOT TO BUY? J LIQ CHROMATOGR R T 2007. [DOI: 10.1081/jlc-120013988] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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12
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Ou J, Dong J, Dong X, Yu Z, Ye M, Zou H. Recent progress in polar stationary phases for CEC. Electrophoresis 2007; 28:148-63. [PMID: 17136736 DOI: 10.1002/elps.200600298] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This review summarizes most of the recent developments in the preparation and application of polar stationary phases for CEC covering the literature published since the year 2004. These polar stationary phases have been adopted for separation of analytes by the modes of packing column CEC, open-tubular CEC (o-CEC) and monolithic column CEC. Currently, development of o-CEC using biomolecules, such as protein and DNA, as the immobilized ligands is highlighted partly due to the simplicity of preparation. Furthermore, monolithic columns have been extended quickly, particularly inorganic materials-based monoliths, such as silica, zirconia, hafnium, etc., as an alternative to packed columns have been developed quickly.
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Affiliation(s)
- Junjie Ou
- National Chromatographic R & A Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
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13
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Ding G, Da Z, Yuan R, Bao JJ. Reversed-phase and weak anion-exchange mixed-mode silica-based monolithic column for capillary electrochromatography. Electrophoresis 2006; 27:3363-72. [PMID: 16944466 DOI: 10.1002/elps.200500931] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A silica-based CEC monolithic column with mixed modes of RP and weak anion-exchange (WAX) was successfully prepared by using the sol-gel technique at mild temperature. The synthesizing procedure was optimized by changing the ratios of tetraethoxysilane (TEOS), aminopropyltriethoxysilane (APTES), and octyltriethoxysilane (C(8)-TEOS) in the mixture. While serving as WAX group, the amino group dominated the charge on the surface of the capillary column and generated an EOF from cathode to anode at low pH. At pH above 7.5, a cathodic EOF was observed due to the full ionization of silanol group and the suppression in the ionization of amino group. The morphology of monolithic columns was examined by SEM, and the performance of column was evaluated in detail by separating different kinds of compounds. As expected, the monolithic column exhibited RP chromatographic behavior for neutral solutes. Fast and efficient separation of six aromatic acids was obtained using acidic mobile phase with column efficiency up to 160,000 plates/m. Symmetrical peaks can be obtained for aromatic amines because positively charged amino groups on the surface can effectively minimize the adsorption of positively charged analytes to the stationary phase.
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Affiliation(s)
- Guosheng Ding
- School of Pharmaceutical Sciences and Technologies, Tianjin University, Tianjin, China
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14
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Qu Q, Tang X, Wang C, Yang G, Hu X, Lu X, Liu Y, Yan C. Preparation of particle-fixed silica monoliths used in capillary electrochromatography. J Sep Sci 2006; 29:2098-102. [PMID: 17017025 DOI: 10.1002/jssc.200600096] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Fused-silica capillarieswere packed with porous 1 microm bare silica microspheres and immobilized by potassium silicate-formamide in order to obtain columns with silica-based monolithic packing. After curing, the particle-fixed monolithic columns were octadecylated insitu with dimethyloctadecylchlorosilane. The columns were mechanically strong and permeable. No noticeable loss in efficiency was found after using a column continuously for 1 month. The performances of the particle-fixed silica monolithic columns were evaluated for CEC under RP conditions. High separation efficiency (about125 200 plates/m) was obtained by using these new types of columns.
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Affiliation(s)
- Qishu Qu
- Jiangsu Key Laboratory of Environmental Materials and Environmental Engineering, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, China.
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15
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Zhang S, Macka M, Haddad PR. Preparation and characterisation of dual-layer latex-coated columns for open-tubular capillary electrochromatographic preconcentration of cations combined in-line with their separation by capillary electrophoresis. Electrophoresis 2006; 27:1069-77. [PMID: 16523457 DOI: 10.1002/elps.200500674] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A dual-layer ion-exchange latex-coated column was prepared and characterised for on-capillary preconcentration of cations using an open-tubular ion-exchange CEC format. After preconcentration, the analyte cations were eluted with a transient isotachophoretic gradient and separated by CE. The latex double layer was established by first coating the negatively charged wall of the capillary with a layer of cationic quaternary ammonium anion-exchange Dionex AS5A latex particles (60 nm diameter), and then coating a layer of anionic sulphonated cation-exchange Dionex CS3 latex particles (300 nm diameter) onto the underlying AS5A layer. The adhesion of layers is based on electrostatic attractions. Several dual-layer capillaries were characterised for their EOF and ion-exchange capacity and this showed that coatings could be prepared reproducibly by a simple flushing procedure. The dual-layer columns exhibited a moderate, pH-independent EOF (ca. 26 x 10(-9 )m2V(-1)s(-1)) and an ion-exchange capacity of 57 microequiv./g (or 2.69 nequiv./column). Using an 8 cm length of coated capillary combined with a 72 cm length of untreated capillary, a method for on-line preconcentration and separation of monovalent organic bases, alkali metal ions and alkaline earth metal ions by CE was developed. Recoveries for the preconcentration step were 48% for 4-methylbenzylammonium, 43% for benzylammonium, 30-32% for alkali metal ions and 71-75% for alkaline earth cations. In all cases, recoveries were reproducible with RSDs being less than 6.2%. The influences of the ion-exchange selectivity coefficient of the analyte and the sample-loading rate on analyte recovery were also examined. The proposed method was utilised for the determination of alkaline earth cations and low microM detection limits were obtained.
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Affiliation(s)
- Shusheng Zhang
- Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Tasmania, Australia
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16
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Gatschelhofer C, Schmid MG, Schreiner K, Pieber TR, Sinner FM, Gübitz G. Enantioseparation of glycyl-dipeptides by CEC using particle-loaded monoliths prepared by ring-opening metathesis polymerization (ROMP). ACTA ACUST UNITED AC 2006; 69:67-77. [PMID: 16556463 DOI: 10.1016/j.jbbm.2006.01.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Accepted: 01/09/2006] [Indexed: 11/27/2022]
Abstract
Novel particle-loaded monolithic capillary electrochromatography (CEC) phases for chiral separations were prepared via ring-opening metathesis polymerization (ROMP) within the confines of fused silica columns with 200 microm i.d. using norborn-2-ene (NBE), 1,4,4a,5,8,8a-hexahydro-1,4,5,8,exo,endo-dimethanonaphthalene (DMN-H6) as monomers, 2-propanol and toluene as porogens, RuCl2(PCy3)2(CHPh) as initiator and silica-based particles containing the chiral selector. By suspending silica particles bearing the chiral selector in the polymerization mixture, particle-based monoliths are easily prepared. This approach has several advantages compared to particle-based separation media: (i) the concept of particle-based monoliths is broadly applicable, as any silica-based chiral phase can be used; (ii) they are inexpensive to prepare; and (iii) the manufacturing process is very simple, no sophisticated packing procedures or the preparation of end frits are required. To show the usefulness of this concept for chiral CEC, the chiral separation performance of particle-loaded CEC monoliths bearing teicoplanin aglycone, chemically bonded to 3 microm silica gel, was investigated for a set of glycyl-dipeptides. Particle-loaded ROMP CEC monoliths showed good separation performance for glycyl-dipeptides.
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Affiliation(s)
- Christina Gatschelhofer
- Institute of Medical Technologies and Health Management, JOANNEUM RESEARCH, Auenbruggerplatz 20/3, A-8036 Graz, Austria
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17
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Kato M, Sakai-Kato K, Toyo'oka T. Silica sol-gel monolithic materials and their use in a variety of applications. J Sep Sci 2005. [DOI: 10.1002/jssc.200500225] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Adu JK, Lau SS, Watson DG, Euerby MR, Skellern GG, Tettey JNA. Capillary electrochromatography of therapeutic peptides on mixed-mode butylmethacrylate monoliths. Electrophoresis 2005; 26:3445-51. [PMID: 16110461 DOI: 10.1002/elps.200500108] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this study, a porous mixed-mode n-alkyl methacrylate-based monolith has been used in the separation of therapeutic peptides. While the sulfonic acid (SCX) moiety derived from 2-acrylamido-2-methyl-1-propanesulfonic acid supports the generation of a stable electroosmotic flow (EOF) at both acidic and basic pH values, the butyl ligands provide the nonpolar sites for chromatographic resolution. The performance of the monolith was evaluated regarding the influence of pH on chromatographic resolution of peptides. The suitability of the butylmethacrylate/SCX monolith for the analysis of therapeutic peptides containing basic centres, for example arginine, at moderately high pH 9.5 and the stability to repeat injections of a mixture of peptides was demonstrated. Separations with efficiencies as high as 5.0 x 10(5) plates/m were obtained and the migration behaviour of the peptides at both low (2.8) and high (9.5) pH values could be rationalised based on their charge, molecular mass/shape and relative hydrophobicities.
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Affiliation(s)
- Joseph K Adu
- Department of Pharmaceutical Sciences, University of Strathclyde, Glasgow, UK
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19
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Karwa M, Hahn D, Mitra S. A sol–gel immobilization of nano and micron size sorbents in poly(dimethylsiloxane) (PDMS) microchannels for microscale solid phase extraction (SPE). Anal Chim Acta 2005; 546:22-29. [DOI: 10.1016/j.aca.2005.05.029] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2005] [Revised: 05/06/2005] [Accepted: 05/11/2005] [Indexed: 10/25/2022]
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20
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Svec F. Recent developments in the field of monolithic stationary phases for capillary electrochromatography. J Sep Sci 2005; 28:729-45. [PMID: 15940819 DOI: 10.1002/jssc.200400086] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This review summarizes the contributions to the rapidly growing area of monolithic columns based on both silica and synthetic polymers for capillary electrochromatography and chip electrochromatography, with a focus on those published during the year 2004. A wide variety of both modified approaches to the "old" monoliths and new monoliths have been reported despite the very short period of time covered. This demonstrates that monolithic stationary phases have become a well-established format in the field of electrochromatography. The simplicity of their preparation as well as the good control over their porous properties and surface chemistries make the monolithic separation media an attractive alternative to capillary columns packed with particulate materials.
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Affiliation(s)
- Frantisek Svec
- Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
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21
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Gübitz G, Schmid MG. Recent advances in chiral separation principles in capillary electrophoresis and capillary electrochromatography. Electrophoresis 2005; 25:3981-96. [PMID: 15597419 DOI: 10.1002/elps.200406173] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This review summarizes recent developments in chiral separation in capillary zone electrophoresis (CZE), electrokinetic chromatography (EKC), and capillary electrochromatography (CEC) covering literature published since the year 2000. New chiral selectors and innovative approaches for CE and CEC are introduced. Recent progress in column technology for CEC is highlighted and the development of new chiral stationary phases is discussed. This review is not dedicated to list applications but will focus on new developments.
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Affiliation(s)
- Gerald Gübitz
- Institute of Pharmaceutical Sciences, Dept. of Pharm. Chemistry, Karl-Franzens-University, Graz, Austria.
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Abstract
A review is presented on the current state of the art and future trends in the development of sol-gel stationary phases for capillary electrochromatography (CEC). The design and synthesis of stationary phases with prescribed chromatographic and surface charge properties represent challenging tasks in contemporary CEC research. Further developments in CEC as a high-efficiency liquid-phase separation technique will greatly depend on new breakthroughs in the area of stationary phase development. The requirements imposed on CEC stationary phase performance are significantly more demanding compared with those for HPLC. The design of CEC stationary phase must take into consideration the structural characteristics that will provide not only the selective solute/stationary phase interactions leading to chromatographic separations but also the surface charge properties that determine the magnitude and direction of the electroosmotic flow responsible for the mobile phase movement through the CEC column. Therefore, the stationary phase technology in CEC presents a more complex problem than in conventional chromatographic techniques. Different approaches to stationary phase development have been reported in contemporary CEC literature. The sol-gel approach represents a promising direction in this important research. It is applicable to the preparation of CEC stationary phases in different formats: surface coatings, micro/submicro particles, and monolithic beds. Besides, in the sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. One remarkable advantage of the sol-gel approach is the mild thermal conditions under which the stationary phase synthesis can be carried out (typically at room temperature). It also provides an effective pathway to integrating the advantageous properties of organic and inorganic material systems, and thereby enhancing and fine-tuning chromatographic selectivity of the created hybrid organic-inorganic stationary phases. This review focuses on recent developments in the design, synthesis, characterization, properties, and applications of sol-gel stationary phases in CEC.
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Affiliation(s)
- Wen Li
- Department of Chemistry, University of South Florida, Tampa, FL 33620-5250, USA
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23
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Abstract
The recent invention and successive commercial introduction of monolithic silica columns has motivated many scientists from both academia and industry to study their use in HPLC. The first paper on monolithic silica columns appeared in 1996. Currently about 200 papers have been published relating to applications and characterization of monolithic silica columns, including monolithic capillaries. This review attempts to give an overview covering various aspects of this new column type in the field of high throughput analysis of drugs and metabolites, chiral separations, analysis of pollutants and food-relevant compounds, as well as in bioanalytical separations such as in proteomics. Some of the applications are described in greater detail. The numerous publications dealing with the physicochemical and chromatographic characterization of monolithic silica columns are briefly summarized.
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Affiliation(s)
- Karin Cabrera
- Merck KGaA, Frankfurter Str 250, D-64293 Darmstadt, Germany.
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Xu L, Feng YQ, Shi ZG, Da SL, Wei F. Preparation of a sulfonated fused-silica capillary and its application in capillary electrophoresis and electrochromatography. J Chromatogr A 2004; 1033:161-6. [PMID: 15072301 DOI: 10.1016/j.chroma.2004.01.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In the present paper, two new methods, sol-gel and chemical bonding methods, were proposed for preparation of sulfonated fused-silica capillaries. In the sol-gel method, a fused-silica capillary was coated with the sol solution obtained by hydrolysis of 3-mercaptopropyltrimethoxysilane (MPTS) and tetramethoxysilane, and followed by age; while in the chemical bonding method, a capillary was chemically bonded directly with MPTS. Then, both the resulting capillaries were oxidized with an aqueous solution of hydrogen peroxide solution (H2O2) (30%, m/m) to obtain the sulfonated capillaries. The electroosmotic flow (EOF) for the sulfonated capillaries was found to remain almost constant within the studied pH range, and greater than that of the uncoated capillary. However, the coating efficiency of the capillary prepared by chemical bonding method was higher than that by sol-gel method, by comparing their magnitude of the EOF, the degree of disguise of the silanol and reproducibility of preparation procedure. The effects of the electrolyte's concentration and the content of methanol (MeOH) on the EOF were also studied. Especially, the study of the apparent pH (pH*) on the EOF in a water-MeOH system was reported. Finally, capillary electrophoretic separation of seven organic acids was achieved within 6.5 min under optimal condition using the chemically bonded sulfonated capillary. Moreover, separation of four alkaloids on the sulfonated capillary was compared with that on uncoated capillary in different conditions. Ion-exchange mechanism was found to play a key role for separation of these four basic analytes on the sulfonated capillary.
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Affiliation(s)
- Li Xu
- Department of Chemistry, Wuhan University, Wuhan 430072, China
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Jiskra J, Claessens HA, Cramers CA. Stationary and mobile phases in capillary electrochromatography (CEC). J Sep Sci 2003. [DOI: 10.1002/jssc.200301305] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kitagawa S, Tsuda T. Behavior of neutral solutes in pressurized flow driven electrochromatography using a mixed stationary phase of ODS and anion-exchange. J Chromatogr A 2003; 995:209-15. [PMID: 12800937 DOI: 10.1016/s0021-9673(03)00519-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The behavior of neutral sample solutes in pressurized flow driven electrochromatography using a mixed stationary phase, which consisted of ODS and anion-exchange (ODS-SAX), was studied. Applications of both positive and negative voltage on a column induced increases in retention factors of sample solutes. The direction of an electroosmotic flow under applications of positive and negative voltage were the same, therefore, the sign of the surface charge density under positive and negative voltage was opposite. We proposed a new equation for the relationship between applied voltage and surface charge density, and the practical electroosmotic flow conformed to this equation. Studying the electroosmotic flow using our proposed equation revealed that the applied negative voltage accelerates the protonation of the quaternary ammonium group and dissociation of the silanol group on packing materials. The retention behavior of a neutral solute was affected by the existence of the charged functional groups. We propose that this phenomenon is applicable to the control of the retention behavior of a sample solute using an electric field.
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Affiliation(s)
- Shinya Kitagawa
- Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan.
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Breadmore MC, Wolfe KA, Arcibal IG, Leung WK, Dickson D, Giordano BC, Power ME, Ferrance JP, Feldman SH, Norris PM, Landers JP. Microchip-based purification of DNA from biological samples. Anal Chem 2003; 75:1880-6. [PMID: 12713046 DOI: 10.1021/ac0204855] [Citation(s) in RCA: 289] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A microchip solid-phase extraction method for purification of DNA from biological samples, such as blood, is demonstrated. Silica beads were packed into glass microchips and the beads immobilized with sol-gel to provide a stable and reproducible solid phase onto which DNA could be adsorbed. Optimization of the DNA loading conditions established a higher DNA recovery at pH 6.1 than 7.6. This lower pH also allowed for the flow rate to be increased, resulting in a decrease in extraction time from 25 min to less than 15 min. Using this procedure, template genomic DNA from human whole blood was purified on the microchip platform with the only sample preparation being mixing of the blood with load buffer prior to loading on the microchip device. Comparison between the microchip SPE (microchipSPE) procedure and a commercial microcentrifuge method showed comparable amounts of PCR-amplifiable DNA could be isolated from cultures of Salmonella typhimurium. The greatest potential of the microchipSPE device was illustrated by purifying DNA from spores from the vaccine strain of Bacillus anthracis, where eventual integration of SPE, PCR, and separation on a single microdevice could potentially enable complete detection of the infectious agent in less than 30 min.
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Affiliation(s)
- Michael C Breadmore
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA
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Lämmerhofer M, Lindner W. Capillary Electrochromatography. JOURNAL OF CHROMATOGRAPHY LIBRARY 2003. [DOI: 10.1016/s0301-4770(03)80037-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Monolithic Columns Prepared from Particles. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0301-4770(03)80025-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Svec F. Capillary electrochromatography: a rapidly emerging separation method. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2002; 76:1-47. [PMID: 12126266 DOI: 10.1007/3-540-45345-8_1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
This overview concerns the new chromatographic method--capillary electrochromatography (CEC)--that is recently receiving remarkable attention. The principles of this method based on a combination of electroosmotic flow and analyte-stationary phase interactions, CEC instrumentation, capillary column technology, separation conditions, and examples of a variety of applications are discussed in detail.
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Affiliation(s)
- Frantisek Svec
- Department of Chemistry, University of California, Berkeley 94720-1460, USA.
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Zou H, Huang X, Ye M, Luo Q. Monolithic stationary phases for liquid chromatography and capillary electrochromatography. J Chromatogr A 2002; 954:5-32. [PMID: 12058917 DOI: 10.1016/s0021-9673(02)00072-9] [Citation(s) in RCA: 283] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A monolithic stationary phase is the continuous unitary porous structure prepared by in situ polymerization or consolidation inside the column tubing and, if necessary, the surface is functionalized to convert it into a sorbent with the desired chromatographic binding properties [J. Chromatogr. A 855 (1999) 273]. Monolithic stationary phases have attracted considerable attention in liquid chromatography and capillary electrochromatography in recent years due to their simple preparation procedure, unique properties and excellent performance, especially for separation of biopolymers. This review summarizes the preparation, characterization and applications of the monolithic stationary phases. In addition, the disadvantages and limitations of the monolithic stationary phases are also briefly discussed.
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Affiliation(s)
- Hanfa Zou
- National Chromatographic Research and Analysis Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
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Wolfe KA, Breadmore MC, Ferrance JP, Power ME, Conroy JF, Norris PM, Landers JP. Toward a microchip-based solid-phase extraction method for isolation of nucleic acids. Electrophoresis 2002; 23:727-33. [PMID: 11891705 DOI: 10.1002/1522-2683(200203)23:5<727::aid-elps727>3.0.co;2-o] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A silica-based solid-phase extraction system suitable for incorporation into a microchip platform (nu-total analytical system; nu-TAS) would find utility in a variety of genetic analysis protocols, including DNA sequencing. The extraction procedure utilized is based on adsorption of the DNA onto bare silica. The procedure involves three steps: (i) DNA adsorption in the presence of a chaotropic salt, (ii) removal of contaminants with an alcohol/water solution, and (iii) elution of the adsorbed DNA in a small volume of buffer suitable for polymerase chain reaction (PCR) amplification. Multiple approaches for incorporation of this protocol into a microchip were examined with regard to extraction efficiency, reproducibility, stability, and the potential to provide PCR-amplifiable DNA. These included packing microchannels with silica beads only, generating a continuous silica network via sol-gel chemistry, and combinations of these. The optimal approach was found to involve immobilizing silica beads packed into the channel using a sol-gel network. This method allowed for successful extraction and elution of nanogram quantities of DNA in less than 25 min, with the DNA obtained in the elution buffer fraction. Evaluation of the eluted DNA indicated that it was of suitable quality for subsequent amplification by PCR.
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Affiliation(s)
- Kelley A Wolfe
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
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Abstract
A review is presented of the most important recent applications of capillary electrochromatography (CEC) for the analysis of acidic, basic, and neutral compounds, of biomolecules, environmental substances, natural products, pharmaceuticals, and chiral compounds. Packed-column CEC (packed-CEC), open-tubular (OT-CEC), as well as pressure-assisted CEC (pseudo-CEC) are hereby considered. Papers published between July 1999 and April 2001 were taken into account. Applications before July 1999 have been reviewed in Electrophoresis 1999, 20, 3027-3065.
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Affiliation(s)
- G Vanhoenacker
- Ghent University, Department of Organic Chemistry, Belgium
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Enlund AM, Isaksson R, Westerlund D. Capillary electrochromatography of tricyclic antidepressants on strong cation exchangers with different pore sizes. J Chromatogr A 2001; 918:211-20. [PMID: 11403450 DOI: 10.1016/s0021-9673(01)00738-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Four cation-exchange materials, possessing propanesulfonic acid ligands, for use in capillary electrochromatography were prepared from different commercially available 5-microm bare-silica particles ranging from 80 to 800 A in pore size. The performance of the materials was investigated at different compositions of the mobile phase (pH, ionic strength, and acetonitrile content) using tricyclic antidepressants and related quaternary ammonium analogues as test analytes. The wide-pore materials promoted pore flow, but this had no positive influence on the performance. The small-pore (highest surface area) particles gave, as could be expected, the best selectivity.
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Affiliation(s)
- A M Enlund
- Uppsala University, Biomedical Center, Division of Analytical Pharmaceutical Chemistry, Sweden.
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Abstract
The present state of the theory of capillary electrochromatography (CEC) is reviewed. Emphasis is placed on electroosmosis and the electrical double layer, and the generally good understanding of the factors affecting the electroosmotic flow in CEC columns. The relation of CEC to other electrically driven separations are described, along with band broadening, and the influence of column temperature in CEC. The theoretical potential of CEC is assessed from the standpoint of current and future column technology, and likely future application areas are described.
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Affiliation(s)
- K D Bartle
- School of Chemistry, University of Leeds, UK.
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Klampfl CW, Buchberger W, Haddad PR. Fast separation of pyrimidine derivatives by capillary electrochromatography on ion-exchange/reversed-phase mixed-mode stationary phases. J Chromatogr A 2001; 911:277-83. [PMID: 11293589 DOI: 10.1016/s0021-9673(01)00515-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This work describes the use of mixed-mode stationary phases which exhibit both strong ion-exchange (either cation-exchange, SCX, or anion-exchange, SAX) and reversed-phase chromatographic characteristics in capillary electrochromatographic separations of pyrimidine derivatives. Different packing materials, namely C6, SCX/C6 and SAX/C6, were compared and the influence of the composition of the carrier electrolyte (concentration of acetonitrile and pH) on the retention behavior of the selected solutes was investigated. A separation of all eight pyrimidine derivatives could be obtained on a 6.5 cm column packed with the SAX/C6 stationary phase in less than 3 min, with good peak shapes and efficiencies in the range 39,000 to 81,000 plates per meter.
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Affiliation(s)
- C W Klampfl
- Department of Analytical Chemistry, Johannes Kepler-University Linz, Austria.
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Abstract
Enantiomer separation by electrochromatography (CEC) can be performed in three modes: (i) open-tubular capillary electrochromatography (o-CEC), in which the chiral selector is physically adsorbed coated, and thermally immobilized or covalently attached to the internal capillary wall; (ii) packed capillary electrochromatography (p-CEC), in which the capillary is either filled with chiral modified silica particles or with an achiral packing material, and a chiral selector is added to the mobile phase; and (iii) monolithic (rod)-capillary electrochromatography (rod-CEC) in which the chiral stationary phase (CSP) consists of a single piece of porous solid. We present an overview on methods and new trends in the field of electrochromatographic enantiomer separation such as CEC with either nonaqueous mobile phases or stationary phases with incorporated permanent charges, or with packing beds consisting of nonporous silica particles or particles with very small internal diameters.
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Affiliation(s)
- D Wistuba
- Institute of Organic Chemistry, University of Tübingen, Germany.
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