Simultaneous quantification of six ephedrines in a Mahwang preparation and in urine by high-performance liquid...

A rapid and reliable high-performance liquid chromatographic method was developed and validated for the simultaneous determination of norephedrine (NE), norpseudoephedrine (NPE), ephedrine (E), pseudoephedrine (PE), methylephedrine (ME) and methylpseudoephedrine (MPE) in both a Mahwang traditional Chinese medicine (TCM) preparation and in urine using alpha-ethylbenzylamine as the internal standard. The method uses a Spherisorb C(18) column for an isocratic elution in a tetraethylammoniumphosphate-methanol mobile phase at a wavelength of 206 nm. The limits of detection of NE, NPE, E, PE, ME and MPE in sample solutions ranged from 0.1 to 0.3 microg[sol ]mL at a signal-to-noise ratio of 3. The within-day precision as calculated from the Mahwang TCM preparation and urine samples was below 6.2 and 1.4% for each analyte. The between-day precision as calculated from the Mahwang TCM preparation and urine samples was below 6.8 and 5.9% for each analyte. The between-day accuracy as determined from the Mahwang TCM preparation and urine samples was below 2.2 and 6.8% for each analyte. The recoveries for six compounds, obtained with compounds spiked into the Mahwang TCM preparation and urine, were found to be more than 93.6%. This method can be successfully applied to doping and excretion rate studies.