Enantioselective HPLC analysis of escitalopram oxalate and its impurities using a cellulose-based chiral stationary phase under normal- and green reversed-phase conditions

Normal-phase and reversed-phase high-performance liquid chromatography methods for the separation of the active pharmaceutical ingredient escitalopram from its (R)-enantiomer impurity have been developed on the cellulose-based Chiralcel OJ-H chiral stationary phase. Both methods share two features: they use ethanol as a cosolvent and are able to give a complete enantioseparation without interference from other associated chiral impurities. With the green eluent mixture ethanol–water–diethylammine 70:30:0.1 (v/v/v), the resolution between escitalopram and (R)-enantiomer was 2.09 at 30°C. The limits of quantification for the (S) and (R) enantiomers were 4.5 and 3.8 μg mL^?1, respectively.