DIRECT HPLC SEPARATION OF ENANTIOMERS OF PANTOPRAZOLE AND OTHER BENZIMIDAZOLE SULFOXIDES USING CELLULOSE-BASED CHIRAL STATIONARY PHASES IN REVERSED-PHASE MODE

A direct, isocratic, and simple reversed-phase HPLC method was describ ed for the separation of enantiomers of the proton pump inhibitor, rac -pantoprazole (PAN) using cellulose-based chiral stationary phases (Ch iralcel OD-R and Chiralcel OJ-R). Some structurally related chiral ben zimidazole sulfoxides, rac-omeprazole (OME) and rac-lansoprazole (LAN) , were also studied. Chiralcel OJ-R was successful in the resolution o f enantiomers of rac-PAN and rac-OME, while Chiralcel OD-R was most su itable for resolving the enantiomers of rac-LAN. Highest enantioselect ivity to rac-PAN and rac-OME was achieved on Chiralcel OJ-R by using a cetonitrile as an organic modifier, whereas methanol afforded better r esolution of rac-LAN on Chiralcel OD-R than acetonitrile. Increases in buffer concentration and column temperature decreased retention and d id not improve the resolution of the enantiomers on both columns. Usin g a mixture of 50 mM sodium perchlorate solution and acetonitrile as a mobile phase at a now rate of 0.5 ml/min, maximum separation factors of 1.26 and 1.13 were obtained for the enantiomers of rac-PAN and rac- OME using a Chiralcel OJ-R column, while maximum separation factor of 1.16 was obtained for the enantiomers of rac-LAN using a Chiralcel OD- R column. (C) 1995 Wiley-Liss, Inc.