SEPARATION AND DETERMINATION OF (I)-EPHEDRINE AND (D)-PSEUDOEPHEDRINE IN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

The separation and determination of (1)-ephedrine (1-Ep)and (d)-pseudoephedrine (d-Ps) in Plasma by high-performance liquid chromatography(RPLC) is described. The newly developed method is based on precolumn derivatization with 5-dimethylaminonaphthalene-1-sulfonyl chloride(DNSCl) in 0.03% triethylamine in acetonitrile at 50 C degrees. The diastereomers formed were separated on a reversed phase column by RPLC with fluorescence detection employing 0.6% phosphate buffer (pH 6.5)-methanol (3:8,v/v) as mobile phase. Clean-up of the ephedrine stereoisomers in plasma was efficiently attained by the combined use of a Sep-pak Cls cartridge and an ion-exchange gel, Carboxymethyl Sephadex LH-20 (CM-LH-20). The detection limit of each ephedrine stereoisomer was 100 pg at a signal-to-noise ratio of 3:1. The plasma-level profile of 1-Ep and d-Ps in a guinea pig was investigated by the newly developed method. The determination of 1-Ep and d-Ps in a volunteer's plasma after oral administration of Xiao Qing-long Heji [an oriental pharmaceutical preparation clinically provided now in China] was also performed.