Cationic cyclodextrins chemically-bonded chiral stationary phases for high-performance liquid chromatography.
Two covalently bonded cationic β-CD chiral stationary phases (CSPs) prepared by graft polymerization of 6(A)-(3-vinylimidazolium)-6-deoxyperphenylcarbamate-β-cyclodextrin chloride or 6(A)-(N,N-allylmethylammonium)-6-deoxyperphenylcarbamoyl-β-cyclodextrin chloride onto silica gel were successfully applied in high-performance liquid chromatography (HPLC). Their enantioseparation capability was examined with 12 racemic pharmaceuticals and 6 carboxylic acids. The results indicated that imidazolium-containing β-CD CSP afforded more favorable enantioseparations than that containing ammonium moiety under normal-phase HPLC. The cationic moiety on β-CD CSPs could form strong hydrogen bonding with analytes in normal-phase liquid chromatography (NPLC) to enhance the analytes' retention and enantioseparations. In reversed-phase liquid chromatography (RPLC), the analytes exhibited their maximum retention when the pH of mobile phase was close to their pK(a) value. Inclusion complexation with CD cavity and columbic/ionic interactions with cationic substituent on the CD rim would afford accentuated retention and enantioseparations of the analytes.
Division of Chemical and Biomolecular Engineering, College of Engineering, Nanyang Technological University, Singapore, Singapore.
Ren-Qi
RQ
Wang
Teng-Teng
TT
Ong
Weihua
W
Tang
Siu-Choon
SC
Ng
D002264:Carboxylic Acids / Q000302:isolation & purification*; D002412:Cations / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods; D004364:Pharmaceutical Preparations / Q000302:isolation & purification*; D058105:Polymerization; D058428:Silica Gel / Q000737:chemistry*; D013237:Stereoisomerism; D047392:beta-Cyclodextrins / Q000737:chemistry*
D002264:Carboxylic Acids; D002412:Cations; D004364:Pharmaceutical Preparations; D047392:beta-Cyclodextrins; D058428:Silica Gel