Phosphorescence for Sensitive Enantioselective Detection in Chiral Capillary Electrophoresis

Abstract

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 alpha-cyclodextrin (alpha-CD), 10 mM carboxymethyl-beta-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 alpha-CD. Under the separation conditions, different phosphorescence lifetimes were obtained for (+)-CQ and (-)-CQ (tau = 384 +/- 8 and 143 +/- 5 micros, 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 alpha-CD. Concentration detection limits were 2 x 10(-7) and 1 x 10(-6) M for (+)-CQ and (-)-CQ, respectively. After correction for the lifetime shortening by triplet-triplet annihilation at higher CQ concentrations, a linear dynamic range was obtained from the detection limit up to 2 mM. The system was used to determine the enantiomeric impurity levels of commercial samples of (+)-CQ and (-)-CQ; 0.2% and 0.1%, respectively.

Time-Resolved Visual Chiral Discrimination of Cysteine Using Unmodified CdTe Quantum Dots

“…Various methods have been reported to distinguish the chirality of amino acids, including high performance liquid chromatography 8–10 , gas chromatography 11 , mass spectrometry 12 , electrochemistry 13–15 , and capillary electrophoresis 16, 17 . However, most of these techniques require complicated sample pretreatment and sophisticated instrumentation which makes them impractical for real-time analysis.…”

Quenched phosphorescence as alternative detection mode in the chiral separation of methotrexate by electrokinetic chromatography

“…Therefore, indirect phosphorescence in sensitized and quenched mode was explored. For this purpose, the phosphorophores BrNS and CQ were tested; both compounds have been used extensively in earlier studies [19, 21–23, 26, 28, 40, 41]. In the sensitized phosphorescence mode, MTX, is excited and transfers its excitation energy to BrNS or CQ, of which the phosphorescence is then observed.…”

Sensitized phosphorescence as detection method for the enantioseparation of bupropion by capillary electrophoresis

“…In this article, we investigate whether room temperature phosphorescence (RTP) is an appropriate alternative detection technique, focusing on the chiral drug bupropion. RTP in liquid deoxygenated solutions has shown to be an attractive luminescence spectroscopic method for detection in CE [12][13][14][15][16][17][18][19]. Contrary to fluorescence, its lifetime is in the 0.01-10 ms range so that scattering problems and impurity fluorescence can be readily avoided by means of time resolution.…”

“…Contrary to fluorescence, its lifetime is in the 0.01-10 ms range so that scattering problems and impurity fluorescence can be readily avoided by means of time resolution. In favorable cases, the interaction between enantiomers of a chiral compound and CDs leads to the formation of diastereoisomeric species that differ in physicochemical properties [15,19]. This is the basis of the separations, and also the phosphorescence lifetime may be different for the diastereoisomeric complexes [19].…”

“…In favorable cases, the interaction between enantiomers of a chiral compound and CDs leads to the formation of diastereoisomeric species that differ in physicochemical properties [15,19]. This is the basis of the separations, and also the phosphorescence lifetime may be different for the diastereoisomeric complexes [19]. Besides direct phosphorescence, where the phosphorescent analyte itself is excited by light of an appropriate wavelength, also indirect phosphorescence can be applied.…”