Development and validation of an enantioselective and chemoselective HPLC method using a Chiralpak IA column to simultaneously quantify (R)-(+)- and (S)-(-)-lansoprazole enantiomers and related impurities.

An accurate and reproducible high-performance liquid chromatographic (HPLC) method has been developed and validated for the direct separation of individual enantiomers of lansoprazole, a potent proton pump inhibitor belonging to the family of the substituted benzimidazoles. The enantiomers were resolved on a Chiralpak IA by using a mobile phase consisting of methyl-tert-butyl ether (MtBE)-ethyl acetate (EA)-ethanol (EtOH)-diethylamine (DEA) in the ratio 60:40:5:0.1 (v/v/v/v). Baseline separation of the enantiomers of lansoprazole was obtained with a resolution factor of 8.14. The standard curves for the two enantiomers were linear (r(2)>0.999) in the concentration range of 10-80microg/ml with a working concentration of about 60microg/ml for each enantiomer. Apparent recovery was 100.8% with a relative standard deviation less than 2%. The limit of quantization for each enantiomer of lansoprazole was 0.22microg/ml. The intra-day precisions were in the range of 0.21-0.36 and 0.59-0.66 while the inter-day precisions were in the range of 0.55-1.24 and 0.66-1.19% in terms of retention times and area response RSD% for (R)-(+)- and (S)-(-)-lansoprazole, respectively. The method was also able to resolve impurities from the enantiomers of lansoprazole.