HPLC on chiralcel OJ-R for enantiomer separation and analysis of ketoprofen, from horse plasma, as the 9-aminophenanthrene derivative

Racemic ketoprofen is a non-steroidal anti-inflammatory drug used to treat musculoskeletal and colic conditions in horses. The enantioselective chiral inversion of ketoprofen administered to horses has been studied by use of cellulose tris (4-methylbenzoate), also known as Chiralcel OJ-R, as chiral stationary phase; acetonitrile - 0.02 M perchlorate buffer (pH 2.0)-methano l, 60:15:25 (v/v/v) was used as mobile phase. Before chromatography, to eff ect adequate chiral interaction with the chiral stationary phase ketoprofen was derivatized with 9-aminophenanthrene, under acid conditions, after sol id-phase (Cls) extraction and then liquid-liquid extraction, to ensure effe ctive removal of endogenous plasma materials. The 9-aminophenanthrene deriv ative of S-ibuprofen was used as internal standard. The enantiomers of keto profen were separated to baseline (Rs = 6.44, alpha = 1.76) within a short analysis time. The results indicate that the bio-inversion of R-ketoprofen to the S isomer is significant in equine species. However, considerable differences in pha rmacokinetic parameters were observed, indicating large inter-animal variat ion.