A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method with hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as chiral selector for the enantiomeric separation of econazole is reported. Enantioseparation of econazole was successfully achieved by the optimized CD-MEKC system containing 40mM HP-gamma-CD, 50mM SDS and 20mM phosphate buffer (pH 8) solution with an analysis time of less than 9min. Calibration curves were linear for the two stereoisomers of econazole (r(2)>0.998). Good repeatabilities in the migration time, peak area and peak height were obtained in terms of RSD% ranging from 0.30 to 7.67%. Combination of solid-phase extraction (SPE) procedure using diol column and the CD-MEKC method was successfully applied to the determination of econazole in a formulated cream sample.
The separation of enantiomers is one of the important fields of modern analytical chemistry, especially for agrochemical and pharmaceutical products because the stereochemistry has a significant influence on the biological activities of compounds. Cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) has become an important capillary electrophoresis mode for enantioseparations. Here, we describe an example of a CD-MEKC method using hydroxypropyl-γ-cyclodextrin as chiral selector and sodium dodecyl sulfate as micellar solution for enantioseparation of triazole fungicides and the drug econazole.
A method for the chiral separation of propiconazole using cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as chiral selector is reported. The use of a mixture of 30 mM HP-gamma-CD, 50mM SDS, methanol-acetonitrile 10%:5% (v/v) in 25 mM phosphate buffer solution was able to separate two enantiomeric pairs of propiconazole. Stacking- and sweeping-CD-MEKC under neutral pH (pH 7) and under acidic condition (pH 3.0) were used as two on-line preconcentration methods to increase detection sensitivity of propiconazole. Good repeatabilities in the migration time, peak area and peak height were obtained in terms of relative standard deviation (RSD). A sensitivity enhancement factor of 100-fold was achieved using sweeping-CD-MEKC at acidic pH. This is the first report on the separation of two pairs of propiconazole enantiomers and all the enantiomers of fenbuconazole and tebuconazole using sweeping-CD-MEKC. The limit of detection (S/N=3) for the three triazole fungicides ranged from 0.09 to 0.1 microg/mL, which is well below the maximum residue limits (MRL) set by Codex Alimentarius Commission (CAC). Combination of solid-phase extraction (SPE) pretreatment and sweeping-CD-MEKC procedure was applied to the determination of selected triazole fungicides in grapes samples spiked at concentration 10-40 times lower than the MRL established by the CAC. The average recoveries of the selected fungicides in spiked grapes samples were good, ranging from 73% to 109% with RSD of 9-12% (n=3).