A novel validated ultra-performance liquid chromatography Method for separation of eszopiclone impurities and its degradants in drug products.

A selective, specific, and sensitive ultra-performance LC (UPLC) method was developed for determination of eszopiclone and its degradation products. The chromatographic separation was performed with a Waters ACQUITY UPLC system and BEH C18 column using gradient elution with mobile phases A and B. Mobile phase A was 0.01 M phosphate buffer with 0.2% (w/v) 1-octane sulfonic acid sodium salt as an ion pair reagent, adjusted pH 2.2 with orthophosphoric acid-acetonitrile (85 + 15, v/v). Mobile phase B was pH 2.2 buffer-acetonitrile (20 + 80, v/v). UV detection was performed at 303 nm. Eszopiclone and its impurities were chromatographed with a total run time of 13 min. A calibration study showed that the response for each of the impurities A, B, C, and D was linear between concentrations of 0.02 and 7.2 microg/mL (r2 > or = 0.999). The method was validated over this range for precision, intermediate precision, accuracy, linearity, and specificity. For the precision study, RSD of each impurity was <5% (n = 6). The method was found to be precise, accurate, linear, and specific. The proposed method was successfully used for determination of eszopiclone impurities in pharmaceutical preparations.