Sensitized enantioselective laser-induced phosphorescence detection in chiral capillary electrophoresis.
The sensitivity of enantioselective cyclodextrin-induced room-temperature phosphorescence detection of camphorquinone (CQ) is enhanced using sensitization via a donor with a high extinction coefficient. The enantiomeric distinction is based on the different phosphorescence lifetimes of (+)-CQ and (-)-CQ after their complexation with α-cyclodextrin (α-CD). The collisional Dexter energy transfer from the selected donor 2,6-naphthalenedisulfonic acid (2,6-NS) to the acceptor CQ is still very efficient despite the inclusion of the acceptor into CD. For coupling to the chiral separation of (±)-CQ in cyclodextrin-based electrokinetic chromatography, the donor was added to the deoxygenated background electrolyte that consisted of 20 mM α-CD, 10 mM carboxymethyl-β-CD, and 25 mM borate buffer at pH 9.0. Time-resolved batch studies on sensitized phosphorescence show a significant enantioselectivity for (+)- and (-)-CQ in the presence of both α-CD and CM-β-CD although the lifetime difference is somewhat reduced with respect to direct excitation. The enantiomers were distinguished after their separation using an online time-resolved detection system. Excitation was performed at 266 nm with a pulsed, small-sized, quadrupled Nd:YAG laser. With 1 × 10(-5) M 2,6-NS, limits of detection of 4.1 × 10(-8) M and 5.2 × 10(-8) M were found for (+)-CQ and (-)-CQ, respectively. The online measured lifetimes were 238 ± 8 μs for (+)-CQ and 126 ± 10 μs for (-)-CQ. The method was used to determine the concentration of (±)-CQ leaching from a cured dental resin into water. The extracts contained 4.7 ± 0.1 × 10(-7) M of both (+)-CQ and (-)-CQ.
Lammers
Ivonne
I
Department of Biomolecular Analysis and Spectroscopy, Laser Centre, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Buijs
Joost
J
Ariese
Freek
F
Gooijer
Cees
C
D002164:Camphor / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D002845:Chromatography; D003505:Cyclodextrins / Q000737:chemistry; D019075:Electrophoresis, Capillary / Q000379:methods*; D007834:Lasers; D008163:Luminescent Measurements; D012117:Resins, Synthetic / Q000737:chemistry; D013237:Stereoisomerism
D003505:Cyclodextrins; D012117:Resins, Synthetic; D002164:Camphor; C553149:camphorquinone