Simultaneous determination of β-artemether and its metabolite dihydroartemisinin in human plasma and urine by a high-performance liquid chromatography-mass spectrometry assay using electrospray ionisation

A sensitive and selective method is described for the determination of P-artemether (AM) and its metabolite dihydroartemisinin (DHA) in human plasma and urine using artemisinin (15) as internal standard. The method consists of a liquid-liquid extraction using 2,2,4-trimethylpentane - ethyl acetate (7:3 v/v) with subsequent evaporation of the supernatant to dryness followed by the analysis of the reconstituted sample by liquid chromatography - mass spectrometry (LC-MS) using positive electrospray ionisation (ESI). The acquisition was performed using a mass range scan and the ions (MH+-CH3OH) m/z 267.2, (MH+-H2O) m/z 267.2 and (MH+) m/z 283.2 for AM, DHA and IS respectively were used for compound quantifications. Chromatography was performed on a Cl 8 reversed-phase column using a gradient of acetonitrile - ammonium acetate 10 mM, glacial acetic acid 0.1% as a mobile phase. The method was validated over a concentration range of 10-1000 ng mL(-1) using 1 mL of human plasma per assay and over a concentration range of 5-500 ng mL(-1) using 2 ml. of human urine per assay. The method was applied to the quantitation of beta-artemether and dihydroartemisinin in human plasma and urine of volunteers participating in a drug pkarmacokinetic study.