Enantiomeric separation of S-zopiclone and its R-enantiomer in bulk drug samples by validated chiral RP-HPLC

Abstract

A simple and selective isocratic chiral RP-HPLC method was developed for the enantiomeric purity determination of S-zopiclone and the quantitative determination of R-zopiclone in bulk drug samples. Enantiomeric separation was achieved using Chiralcel OD-RH 150 x 4.6 mm, 5 microm particle size column at 25 degrees C using a mobile phase of 10 mM ammonium acetate and acetonitrile in ratio of 60:40 (v/v) as mobile phase at a flow rate of 1.0 mL x min(-1) and UV detection at 306 nm. The method resolves the R-zopiclone and S-zopiclone with resolution (Rs) greater than 1.6. The limit of detection (LOD) and limit of quantitation (LOQ) of the R-enantiomer were 0.12 microg x mL(-1) and 0.40 microg x mL(-1) respectively, for 10 microL injection volume. The percentage RSD of the peak area of six replicate injections of R-zopiclone at LOQ concentration was 4.6. The percentage recoveries of R-enantiomer from S-zopiclone were ranged from 97.3 to 99.8. Developed method was found to be selective in presence potential impurities. The developed chiral RP-HPLC method was validated with respect to precision, linearity, accuracy, robustness and ruggedness. The test solution and mobile phase was found to be stable up to 24 h after preparation.