A new procedure for enantioseparation of chiral drugs based on two separated chiral beds on capillary electrophoresis

In the last decades, a growing interest has been paid to the separation, detection and quantification of enantiomers in pharmaceutical, agricultural, environmental, and food analysis. Today capillary electrophoresis, as one of the most used techniques for enantioseparation is highly regarded and direct addition of a chiral substance known as a chiral selector (CS) to the background electrolyte (BGE) is a common method of chiral separation in CE [1-4].In this study, a novel chiral CE procedure was developed using two separated chiral beds on capillary electrophoresis system for the simultaneous enantioseparation of two basic drugs. In this new method, two different background electrolytes (BGEs) were filled in two different parts of a capillary column. The used BGEs contained the same composition except for two different chiral selectors (CSs). In other words, two different CSs were simultaneously applied to the chiral separation, without being mixed together. The proposed method was compared with mixed CS-CE system. Finally, the optimized method using two separated chiral beds was validated and applied to the enantioseparation of chlorpheniramine and citalopram in commercial tablets. The best results were obtained using a fused silica capillary with phosphate as the running buffer (100 mM, pH 3.0) containing 10 mM HP-β-cyclodextrin in the first part and 10% (w/v) maltodextrin in the second part, and detected by UV spectrometry at 214 nm. The capillary column temperature was set to 25°C, with a voltage of 18 kV applied for the separation. The linear range of the method was over 10 to 1000 mg/L for all enantiomers of chlorpheniramine and citalopram. The quantification (S/N =10) and detection limits (S/N = 3) were found to be 10 and 3 mg/L, respectively, for all enantiomers. This is a simple and flexible method which exhibited good precision with respect to the resolution and migration times and allows one to separate enantiomers that cannot be separated using either one CS or mixed CSs.