title: C18-COOH Silica: Preparation, Characterisation and Its Application in Purification of Quaternary Ammonium Alkaloids from Coptis chinensis.
abstract: BACKGROUND
  Traditional methods for isolating and purifying quaternary ammonium alkaloids from Coptis chinensis do not discriminate the target alkaloids from co-extractives. Mixed-mode analytical chromatography has the potential to improve the separation of analytes in more complex extracts and, when used in a solid-phase extraction mode, improve the purity of isolated compounds.
  
  
  OBJECTIVE
  To examine the high-performance liquid chromatographic separation capabilities of a mixed-mode, silica-based adsorbent and its application to the purification of quaternary ammonium alkaloids from Coptis chinensis based on solid-phase extraction.
  
  
  METHODS
  The C18-COOH silica was prepared via "thiol-ene" click chemistry. Its chromatographic performance was firstly investigated. It was employed as the solid-phase extraction sorbent to purify quaternary ammonium alkaloids.
  
  
  RESULTS
  Hydrophobic, attractive/repulsive electrostatic and ion-exchange interactions were demonstrated to be the possible retention mechanisms of a C18-COOH silica stationary phase, which could separate analytes of various properties. In addition, to purify quaternary ammonium alkaloids from Coptis chinensis, the solid-phase extraction approach based on the C18-COOH silica provided a slightly higher purification efficiency (6.7%) than an alkaloid-salt precipitation protocol (5.3%). The method had satisfactory reproducibility, re-using the same solid-phase extraction column three times, with relative standard deviations ranging from 1.99% to 8.02% for the six target alkaloids.
  
  
  CONCLUSIONS
  A multi-functionalised silica was synthesised via "click chemistry". As the high-performance liquid chromatographic stationary phase, the C18-COOH silica could be operated in trimodal reversed-phase/weak cation exchange/hydrophilic interaction mode. The C18-COOH silica also exhibited potential as solid-phase extraction sorbent in the purification of quaternary ammonium alkaloids from complex matrices. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan, 430030, China.|Tianjin Key Laboratory of Food Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, 300134, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Long
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Yao
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Mao
authors.initials: M
authors.lastname: Ye
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Li
authors.identifier: http://orcid.org/0000-0001-6875-9396
authors.initials: L
authors.lastname: Xu
mesh_terms: D000327:Adsorption; D000470:Alkaloids / Q000302:isolation & purification*; D064751:Ammonium Compounds / Q000302:isolation & purification*; D039323:Coptis / Q000737:chemistry*; D015203:Reproducibility of Results; D012822:Silicon Dioxide; D052616:Solid Phase Extraction
chemical_list: D000470:Alkaloids; D064751:Ammonium Compounds; D012822:Silicon Dioxide
keywords: Mixed-mode chromatography; purification; quaternary ammonium alkaloids