Phosphorescence for Sensitive Enantioselective Detection in Chiral Capillary Electrophoresis

Enantioselective phosphorescence lifetime detection was combined with chiral cyclodextrin-based electrokinetic chromatography for the analysis of camphorquinone (CQ). A time-gated detection system based on a pulsed light-emitting diode for excitation at 465 nm was developed for the online lifetime determination. The background electrolyte for the chiral separation consisted of 20 mM α-cyclodextrin (α-CD), 10 mM carboxymethyl- β-CD, and 25 mM borate buffer at pH 9.0. The separation of (+)-CQ and (-)-CQ is caused by a difference in association constants of these enantiomers with α-CD. Under the separation conditions, different phosphorescence lifetimes were obtained for (+)-CQ and (-)-CQ (τ = 384 ± 8 and 143 ± 5 μs, respectively), which could be used to distinguish the enantiomers. This selectivity in detection is based on a difference in protection of the enantiomers against phosphorescence quenching after their complexation with α-CD. Concentration detection limits were 2 × 10