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Zhu B, Qiu H, Ma C, Chen S, Zhu J, Tong S. Recent progress on chiral extractants for enantioselective liquid-liquid extraction. J Chromatogr A 2023; 1709:464389. [PMID: 37741223 DOI: 10.1016/j.chroma.2023.464389] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 09/16/2023] [Accepted: 09/16/2023] [Indexed: 09/25/2023]
Abstract
As the demand for enantiopure compounds increases, chiral separation has become increasingly important in many fields. Enantioselective liquid-liquid extraction is an up-and-coming technology for enantiomeric separation because it is highly efficient and easy to be scaled up. The key factor for enantioselective liquid-liquid extraction is the development of novel chiral extractants with high enantiorecognition performance. With successful studies on catalytically active metal complexes as chiral extractants, novel chiral extractants can be screened and designed from the field of asymmetric catalysis. Chiral ionic liquids, sulfobutylether-β-cyclodextrins bonded magnetic nanoparticles and 2,2',3,3'-tetrahydro-1,1'-spirobi[indene]-7,7'-diol (SPINOL) based phosphoric acid host show unique potential ability in enantioselective liquid-liquid extraction and they deserve further study. Brief principles, extraction equipment and solvent systems in enantioselective liquid-liquid extraction are presented in the present paper, and recent progress in development of new chiral extractants in the past decade is mainly reviewed, including metal complexes, cyclodextrins, ionic liquids, tartrate acids and crown ethers.
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Affiliation(s)
- Beibei Zhu
- College of Pharmaceutical Science, Zhejiang University of Technology, Moganshan Campus, Gongda Road 1, Huzhou 313200, China
| | - Huiyun Qiu
- College of Pharmaceutical Science, Zhejiang University of Technology, Moganshan Campus, Gongda Road 1, Huzhou 313200, China
| | - Chenlei Ma
- College of Pharmaceutical Science, Zhejiang University of Technology, Moganshan Campus, Gongda Road 1, Huzhou 313200, China
| | - Songlin Chen
- College of Pharmaceutical Science, Zhejiang University of Technology, Moganshan Campus, Gongda Road 1, Huzhou 313200, China
| | - Junchao Zhu
- College of Pharmaceutical Science, Zhejiang University of Technology, Moganshan Campus, Gongda Road 1, Huzhou 313200, China
| | - Shengqiang Tong
- College of Pharmaceutical Science, Zhejiang University of Technology, Moganshan Campus, Gongda Road 1, Huzhou 313200, China.
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2
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Sun W, Chen B, You H, Fang L, Qian J, Tong S. Enantioseparation of N-methyl duloxetine, duloxetine and fluoxetine by countercurrent chromatography using anionic β-cyclodextrin as chiral selector. J Sep Sci 2022; 45:3022-3030. [PMID: 35598113 DOI: 10.1002/jssc.202200151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/26/2022] [Accepted: 05/19/2022] [Indexed: 11/08/2022]
Abstract
Two anionic. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Wenyu Sun
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Ben Chen
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Haibo You
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Liqun Fang
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Junqing Qian
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Shengqiang Tong
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310032, China
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3
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Recent Advances on Chiral Mobile Phase Additives: A Critical Review. JOURNAL OF ANALYSIS AND TESTING 2022. [DOI: 10.1007/s41664-022-00222-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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4
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Grybinik S, Bosakova Z. An overview of chiral separations of pharmaceutically active substances by HPLC (2018-2020). MONATSHEFTE FUR CHEMIE 2021; 152:1033-1043. [PMID: 34456367 PMCID: PMC8382579 DOI: 10.1007/s00706-021-02832-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/01/2021] [Indexed: 02/07/2023]
Abstract
This review provides a brief survey of chiral separation of pharmaceutically active substances published over the last 3 years (2018-2020). Chiral separation of drugs is an important area of research. The control of enantiomeric purity and determination of individual enantiomeric drug molecules is a necessity especially for clinical, analytical, and regulatory purposes. Among chromatographic resolution methods, high-performance liquid chromatography based on chiral stationary phases remains the most popular and effective method used for chiral separation of various drugs. In this review, attention is paid to several classes of chiral stationary phases that have been the most frequently used for drug enantioseparation during this period. GRAPHIC ABSTRACT
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Affiliation(s)
- Sofiya Grybinik
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
| | - Zuzana Bosakova
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
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Sun W, Bao H, Qian J, Tong S. Enantioseparation of ondansetron by countercurrent chromatography using sulfobutyl ether-β-cyclodextrin as chiral selector. J Sep Sci 2020; 44:922-930. [PMID: 33284511 DOI: 10.1002/jssc.202001118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/28/2020] [Accepted: 12/02/2020] [Indexed: 11/08/2022]
Abstract
Ondansetron, a highly selective 5-hydroxytryptamine 3 receptor antagonist, was successfully enantioseparated by recycling countercurrent chromatography using sulfobutyl ether-β-cyclodextrin as chiral selector. Important factors for the enantioseparation were optimized, including different organic solvent, type of substituted β-cyclodextrin, pH of aqueous phase, concentration of chiral selector, and separation temperature. A biphasic solvent system composed of n-hexane: n-butyl acetate: 0.1 mol/L phosphate buffer solution pH 9.2 with 50 mmol/L of sulfobutyl ether-β-cyclodextrin (2.5:7.5:10, v/v/v) was selected. Under optimized separation conditions, 5 mg of ondansetron was enantioseparated using recycling countercurrent chromatography, yielding 1.2 and 1.5 mg of ondansetron enantiomers with 97.5 and 95.8% purity and the recovery reached 48-60%.
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Affiliation(s)
- Wenyu Sun
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Honglei Bao
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Junqing Qian
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Shengqiang Tong
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
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Jin Y, Bao H, Sun W, Sun H, Zhao S, Wang X, Tong S. Enantioseparation of 2-(4-chlorophenyl)succinic acid by countercurrent chromatography and investigation of injection volume on resolution. J Sep Sci 2020; 44:752-758. [PMID: 33247875 DOI: 10.1002/jssc.202000860] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 11/01/2020] [Accepted: 11/24/2020] [Indexed: 11/10/2022]
Abstract
2-(4-Chlorophenyl)succinic acid was successfully enantioseparated by countercurrent chromatography using hydroxypropyl-β-cyclodextrin as chiral selector. A two-phase solvent system composed of n-hexane-ethyl acetate-0.1 mol/L phosphate buffer with pH 2.65 (5:5:10, v/v) was selected. Enantioselective liquid-liquid extraction was used to optimize the enantioseparation conditions. Meanwhile, the influence of injection volume on resolution in countercurrent chromatography was investigated and a linear relationship between the inflection point of injection volume and sample loading was tentatively obtained. The peak resolution will decrease significantly when the injection volume over the inflection point was used. In addition, it could be found that the smaller amount of sample loading, the larger impact of injection volume on resolution could be observed, which might serve as a good reference for the selection of sample volume in enantioseparations by countercurrent chromatography. Under optimized conditions, 20 mg of 2-(4-chlorophenyl)succinic acid racemate dissolved in 10 mL of aqueous phase was successfully enantioseparated by countercurrent chromatography. The recovery for both of the enantiomer of (±)-2-(4-chlorophenyl)succinic acid reached within 70-75% with a purity of 99.0%.
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Affiliation(s)
- Yang Jin
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Honglei Bao
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Wenyu Sun
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Hengmian Sun
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Shanshan Zhao
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Xiang Wang
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Shengqiang Tong
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
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7
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Liquid-liquid chromatography in enantioseparations. J Chromatogr A 2020; 1626:461345. [DOI: 10.1016/j.chroma.2020.461345] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 06/12/2020] [Accepted: 06/12/2020] [Indexed: 12/20/2022]
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8
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Duan WD, Huang XY, Di DL. Chiral counter-current chromatography: A survey of its instrument, mechanism, procedure, and applications. Chirality 2020; 32:1264-1283. [PMID: 32692440 DOI: 10.1002/chir.23262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 06/06/2020] [Accepted: 06/16/2020] [Indexed: 11/09/2022]
Abstract
The chiral separation by counter-current chromatography has made great progress in the past three decades. It has become increasingly popular in the field of chiral separation, and many applications have been introduced during the last years. This review mainly focuses on the current topics, applications, and trends in chiral separation by counter-current chromatography. It contains the development of modern counter-current chromatography apparatus, theory of counter-current chromatography, overview of applications of chiral counter-current chromatography enantioseparation, its current situation, and challenges. At last, some conclusions and perspectives also have been discussed in this review.
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Affiliation(s)
- Wen-Da Duan
- CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xin-Yi Huang
- CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China
| | - Duo-Long Di
- CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China
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9
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Pinto MM, Fernandes C, Tiritan ME. Chiral Separations in Preparative Scale: A Medicinal Chemistry Point of View. Molecules 2020; 25:E1931. [PMID: 32326326 PMCID: PMC7221958 DOI: 10.3390/molecules25081931] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 04/18/2020] [Accepted: 04/19/2020] [Indexed: 01/22/2023] Open
Abstract
Enantiomeric separation is a key step in the development of a new chiral drug. Preparative liquid chromatography (LC) continues to be the technique of choice either during the drug discovery process, to achieve a few milligrams, or to a scale-up during the clinical trial, needing kilograms of material. However, in the last few years, instrumental and technical developments allowed an exponential increase of preparative enantioseparation using other techniques. Besides LC, supercritical fluid chromatography (SFC) and counter-current chromatography (CCC) have aroused interest for preparative chiral separation. This overview will highlight the importance to scale-up chiral separations in Medicinal Chemistry, especially in the early stages of the pipeline of drugs discovery and development. Few examples within different methodologies will be selected, emphasizing the trends in chiral preparative separation. The advantages and drawbacks will be critically discussed.
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Affiliation(s)
- Madalena M.M. Pinto
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia da Universidade do Porto, 4050-313 Porto, Portugal; (C.F.); (M.E.T.)
- Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, 4050-208 Matosinhos, Portugal
| | - Carla Fernandes
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia da Universidade do Porto, 4050-313 Porto, Portugal; (C.F.); (M.E.T.)
- Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, 4050-208 Matosinhos, Portugal
| | - Maria E. Tiritan
- Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia da Universidade do Porto, 4050-313 Porto, Portugal; (C.F.); (M.E.T.)
- Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Edifício do Terminal de Cruzeiros do Porto de Leixões, 4050-208 Matosinhos, Portugal
- CESPU, Instituto de Investigação e Formação Avançada em Ciências e Tecnologias da Saúde (IINFACTS), 4585-116 Gandra PRD, Portugal
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10
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Qiu X, Sun W, Wang C, Yan J, Tong S. Enantioseparation of acetyltropic acid by countercurrent chromatography with sulfobutyl ether-β-cyclodextrin as chiral selector. J Sep Sci 2019; 43:681-688. [PMID: 31714009 DOI: 10.1002/jssc.201900730] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/10/2019] [Accepted: 11/08/2019] [Indexed: 12/19/2022]
Abstract
Acetyltropic acid is an important synthetic intermediate for preparation of tropane alkaloid derivatives, which can be used as anticholinergic drugs, deliriants, and stimulants. In the present work, acetyltropic acid was successfully enantioseparated by countercurrent chromatography using sulfobutyl ether-β-cyclodextrin as chiral selector. A biphasic solvent system composed of n-butyl acetate/n-hexane/0.1 mol/L citrate buffer at pH = 2.2 containing 0.1 mol/L of sulfobutyl ether-β-cyclodextrin (7:3:10, v/v) was selected, which produced a suitable distribution ratio DS = 1.14, DR = 2.31 and a high enantioseparation factor α = 2.03. Baseline separation was achieved for preparative enantioseparation of 50 mg of racemic acetyltropic acid. A method for chiral analysis of acetyltropic acid by conventional reverse phase liquid chromatography with hydroxylpropyl-β-cyclodextrin as mobile phase additive was established, and formation constants of inclusion complex were determined. It was found that different substituted β-cyclodextrin should be selected for enantioseparation of acetyltropic acid by countercurrent chromatography and reverse phase liquid chromatography.
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Affiliation(s)
- Xujun Qiu
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Wenyu Sun
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Chaoyue Wang
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Jizhong Yan
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
| | - Shengqiang Tong
- College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, P. R. China
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11
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Wu D, Pan F, Tan W, Gao L, Tao Y, Kong Y. Recent progress of enantioseparation under scale production (2014–2019). J Sep Sci 2019; 43:337-347. [DOI: 10.1002/jssc.201900682] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 10/11/2019] [Accepted: 10/28/2019] [Indexed: 12/11/2022]
Affiliation(s)
- Datong Wu
- Jiangsu Key Laboratory of Advanced Materials and TechnologySchool of Petrochemical EngineeringChangzhou University Changzhou P. R. China
| | - Fei Pan
- Jiangsu Key Laboratory of Advanced Materials and TechnologySchool of Petrochemical EngineeringChangzhou University Changzhou P. R. China
| | - Wensheng Tan
- Changzhou Key Laboratory of Large Plastic Parts Intelligence ManufacturingChangzhou College of Information Technology Changzhou P. R. China
| | - Li Gao
- Jiangsu Key Laboratory of Advanced Materials and TechnologySchool of Petrochemical EngineeringChangzhou University Changzhou P. R. China
| | - Yongxin Tao
- Jiangsu Key Laboratory of Advanced Materials and TechnologySchool of Petrochemical EngineeringChangzhou University Changzhou P. R. China
| | - Yong Kong
- Jiangsu Key Laboratory of Advanced Materials and TechnologySchool of Petrochemical EngineeringChangzhou University Changzhou P. R. China
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12
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Preparation of a hydroxypropyl-β-cyclodextrin functionalized monolithic column by one-pot sequential reaction and its application for capillary electrochromatographic enantiomer separation. J Chromatogr A 2019; 1603:269-277. [PMID: 31279475 DOI: 10.1016/j.chroma.2019.06.044] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 06/21/2019] [Accepted: 06/22/2019] [Indexed: 02/08/2023]
Abstract
In this study, a hydroxypropyl-β-cyclodextrin (HP-β-CD) functionalized monolithic capillary column was prepared by one-pot sequential reaction for the first time. The preparation of the HP-β-CD functionalized monolithic column involves two sequential reactions in one pot: (1) the ring opening reaction between HP-β-CD and glycidyl methacrylate (GMA) catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); (2) the copolymerization of GMA-HP-β-CD, ethylene dimethacrylate (EDMA) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS). A series of monolithic columns were successfully prepared by varying the temperature of the ring opening reaction or several copolymerization parameters (the type and composition of porogenic solvents, ratio of GMA-HP-β-CD to EDMA and polymerization temperature). Then, the morphologies and structures of the resulting monolithic stationary phases were characterized by optical microscopy, scanning electron microscopy (SEM) and nitrogen adsorption analysis. Raman spectroscopy clearly indicated the successful bonding of HP-β-CD onto the monolith. When the prepared chiral stationary phase (CSP) was applied for the separation of a set of racemic compounds by capillary electrochromatography (CEC), including racemic anticholinergic drugs, β-adrenergic drugs, meptazinol and its intermediates, satisfactory separation selectivities were obtained. Additionally, the column also showed excellent separation abilities towards four flavanone glycosides epimers. Furthermore, the prepared monolithic columns exhibited satisfactory stability and reproducibilities of retention time, resolution and column efficiency. These results demonstrated the potential and usefulness of the developed one-pot sequential strategy in the preparation of other derivatized CD functionalized monolithic columns.
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Quan KJ, Huang XY, Gong Y, Pei D, Duan WD, Di DL. Counter-current chromatography melamine-modified column and its separation mechanism. J Sep Sci 2018; 42:547-555. [PMID: 30427121 DOI: 10.1002/jssc.201800914] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/09/2018] [Accepted: 11/04/2018] [Indexed: 11/08/2022]
Abstract
In this work, to further verify and develop the novel counter-current chromatography modified column separate mode, a melamine modified counter-current chromatography column was prepared. Meanwhile, the modified counter-current chromatography column was used to separate stevioside and rebaudioside A with the same partition coefficient in chosen solvent system to evaluate its separation efficiency. The results show that because of the presence of intermolecular forces between melamine and model compounds, better separation could be achieved on the modified column while it's almost impossible to be separated on the unmodified column. So the results of this research further show that column modified method is a possible approach to further increase the separation ability of counter-current chromatography. Take advantage of large sample handing capacity of counter-current chromatography, the mothed may have great potential to be an efficient method of separation and preparation enantiomer compounds.
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Affiliation(s)
- Kai-Jun Quan
- Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Chinese Academy of Sciences, Lanzhou Institute of Chemical Physics, Lanzhou, P. R. China.,University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Xin-Yi Huang
- Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Chinese Academy of Sciences, Lanzhou Institute of Chemical Physics, Lanzhou, P. R. China
| | - Yuan Gong
- Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Chinese Academy of Sciences, Lanzhou Institute of Chemical Physics, Lanzhou, P. R. China.,University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Dong Pei
- Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Chinese Academy of Sciences, Lanzhou Institute of Chemical Physics, Lanzhou, P. R. China
| | - Wen-Da Duan
- Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Chinese Academy of Sciences, Lanzhou Institute of Chemical Physics, Lanzhou, P. R. China.,University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Duo-Long Di
- Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Chinese Academy of Sciences, Lanzhou Institute of Chemical Physics, Lanzhou, P. R. China
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