Determination of amiodarone and desethylamiodarone in human plasma by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry with an ion trap detector.

A sensitive and specific high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS-MS) method has been developed for the simultaneous determination of amiodarone and desethylamiodarone in human plasma. After the addition of the internal standard tamoxifen, plasma samples were extracted using Oasis MCX solid-phase extraction cartridges. The compounds were separated on a 5 microm Symmetry C18 (Waters) column (150 x 3.0 mm, internal diameter) with a mobile phase of acetonitrile-0.1% forrmic acid (46:54, v/v) at a flow-rate of 0.5 ml/min. The overall extraction efficiency was more than 89% for both compounds. The assay was sensitive down to 1 microg/l for amiodarone and down to 0.5 microg/l for desethylamiodarone. Within-run accuracies for quality-control samples were between 95 and 108% of the target concentration, with coefficients of variation <8%. The proposed method enables the unambiguous identification and quantitation of amiodarone and desethylamiodarone in both clinical and forensic specimens.