Thesis (M.Sci.)--Chulalongkorn University, 2003

A sensitive and highly specific assay method was developed for the determination of dihydroartemisinin in human plasma by liquid chromatography - tandem mass spectrometry (LC-MS/MS) using electrospray ionization (ESI) as an interface. Artemisinin was used as internal standard. A simple liquid-liquid extraction with 1-chlorobutane-isooctane (55:45,v/v) was used to isolate dihydroartemisinin from plasma. The mobile phase was composed of acetonitrile-water (50:50,v/v) and chromatographic separations were achieved on a luna 3 mm C[subscript18] column (150 x 2.00 mm). The quantitation was operated in positive ion multiple reaction monitoring (MRM) mode. Dihydroartemisinin produced a precursor ion ([M+Na]+) at m/z of 307 and corresponding product ion at m/z of 261 and 163. And internal standard (artemisinin) produced a precursor ion ([M+Na]+) at m/z of 305 and corresponding product ion at m/z of 151. The calibration curve was linear over a concentration range of 5-200 ng/ml, with intra- and inter day accuracy and precision were within the acceptable range. The method was applied to the quantification of dihydroartemisinin in human plasma for pharmacokinetic analyses.