Sensitive liquid chromatographic-tandem mass spectrometric method for the determination of fluoxetine and its primary active metabolite norfluoxetinein human plasma

A sensitive method for the simultaneous determination of fluoxetine and its major active metabolite norfluoxetine in plasma was developed, using high- performance liquid chromatographic separation with tandem mass spectrometri c detection. The samples were extracted from alkalised plasma with hexane-i soamyl alcohol (98.2, v/v) followed by back-extraction into formic acid (2% ). Chromatography was performed on a Phenomenex (R) Luna C-18 (2) 5 mum, 15 0X2 mm column with a mobile phase consisting of acetonitrile-0.02% formic a cid (340:660, v/v) at a flow-rate of 0.35 ml/min. Detection was achieved by a Perkin-Elmer Sciex API 2000 mass spectrometer (LC-MS-MS) set at unit res olution in the multiple reaction monitoring mode. TurboIonSpray ionisation was used for ion production. The mean recoveries for fluoxetine and norfluo xetine were 98 and 97%, respectively, with a lower limit of quantification set at 0.15 ng/ml for the analyte and its metabolite. This assay method mak es use of the increased sensitivity and selectivity of mass spectrometric ( MS-MS) detection to allow for a more rapid (extraction and chromatography) and sensitive method for the simultaneous determination of fluoxetine and n orfluoxetine in human plasma than has previously been described. (C) 2001 E lsevier Science BN. All rights reserved.