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Zwitterionic codeine‐derived methacrylate monoliths for enantioselective capillary electrochromatography of chiral acids and chiral bases
Author(s) -
CarrascoCorrea Enrique Javier,
Ferri Martina,
Woiwode Ulrich,
Ma Yubo,
HerreroMartínez José Manuel,
RamisRamos Guillermo,
Lindner Wolfgang,
Lämmerhofer Michael
Publication year - 2018
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201800126
Subject(s) - capillary electrochromatography , chemistry , isocyanate , enantiomer , monolith , methacrylate , electrochromatography , enantiopure drug , polymer chemistry , capillary electrophoresis , enantioselective synthesis , organic chemistry , chromatography , copolymer , polymer , catalysis , polyurethane
Thiol‐ene click reaction of N ‐acetyl‐L‐cysteine methyl ester to codeine, followed by reaction with allyl isocyanate and hydrolysis to the corresponding zwitterionic chiral selector and its subsequent bonding to the surface of a methacrylate monolith provided a new chiral capillary column for enantiomer separation of chiral acids and chiral bases. First, the epoxy groups of a poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) monolith were converted into amine residues, followed by reaction with allylglycidyl ether. In this way, a spacer arm was bonded to the surface before coating and cross‐linking poly(3‐mercaptopropyl methylsiloxane) (PMPMS) via radical addition (thiol‐ene click reaction) to the surface. In order to improve the performance of the monolithic chiral stationary phase, thio ether and residual thiol groups were oxidized to sulfonyl and sulphonate groups, respectively. This novel chiral stationary phase (CSP) was evaluated by capillary electrochromatography (CEC) using two chiral model compounds, namely N ‐3,5‐dinitrobenzoyl‐R,S‐leucine (retained by anion‐exchange mechanism) and mefloquine (by cation‐exchange process). The ion‐exchange retention mechanism on the CSP was characterized for these two counterionic model solutes by varying the mobile phase composition, including the nature of solvents, the concentration of counter‐ions and co‐ions, and the acid‐to‐base ratio. A series of chiral β‐blockers and amino acid derivatives was used to further check the performance of the modified monolith under the optimal conditions. Several enantiomers were baseline resolved with reasonable peak efficiencies (up to 60,000 theoretical plates per meter for the second eluted enantiomer).