Internally standardized simultaneous assay of propafenone and 5-hydroxypropafenone enantiomers in human plasma by means of high performance liquid chromatography.

A high performance liquid chromatographic method with internal analog standardization for the quantification of propafenone and 5-hydroxypropafenone enantiomers in human plasma is described. The method comprises extraction from alkalinized plasma into a toluene/diethylether phase (9:1), separation of the optical antipodes on a silica gel column using N-tert-Boc-(L)-proline as the chiral additive to the mobile phase and UV detection. A detection limit of 10 pmol/assay was established for the propafenone enantiomers, whereas for the optical antipodes of 5-hydroxypropafenone the limit was around 50 pmol/assay. Under routine conditions the limit of quantification (variation coefficient 15%) for the propafenone enantiomers is about 13 pmol/assay and for the 5-hydroxypropafenone enantiomers it is 66 pmol/assay. The determination method for the enantiomers is not impaired by the other metabolites. The suitability of the method for human pharmacology studies is demonstrated with samples obtained from healthy subjects.