Quantitation of R- and S-propafenone and of the main metabolite in plasma

Several methods for the determination of racemic propafenone or its enantiomers as well of the main metabolite R,S-5-hydroxypropafenone are known from the literature. The method described here enables the simple simultaneous quantification of R- and S-propafenone and of R,S-5-hydroxypropafenone in human plasma. The method is based on an HPLC separation using a Chiralpak AD column. High recovery rates (80-95%) were achieved by means of a liquid-liquid-extraction at pH 11 with dichloromethane as solvent. The separation on the chiral carrier were carried out with n-hexane/2-propanol; the addition of diethylamine is useful. The obtained capacity factors are k' = 2.36 for R-propafenone and k' = 3.82 for S-propafenone. R,S-propanolol and R,S-metoprolol were used as internal standards. The method described can be used for pharmacokinetic trials in man with the following limits of quantitation: 10 ng/ml for R- and S-propafenone and 20 ng/ml for R,S-5-hydroxypropafenone.