Departments of Pharmacology and

Sorafenib is a multikinase inhibitor and an oral anticancer drug approved for the treatment of patients with advanced renal cell carcinoma and those with unresectable hepatocellular carcinoma. The pur-pose of this study was to develop an efficient method of the determination of sorafenib in human plasma using tandem mass spectrometry coupled with liquid chromatography (LC/MS/MS) and vali-date the method by the guidelines of the Korean Food and Drug Administration (KFDA). Plasma sam-ples (100 μl) were added with chlorantraniliprole as an internal standard and then mixed with the 0.1 % formic acid-containing extraction solution composed of isopropyl alcohol and ethyl acetate (1:4, v/v). After centrifugation, the supernatant was concentrated at 45°C under negative pressure and cen-trifugal force. The residue was reconstituted with a mobile phase and injected into the HPLC instru-ment using a reverse phase Waters XTerra TM C18 column (particle size 3.5 μm). Liquid chromatog-raphy was carried out within the run time of 5 min using a mobile phase composed of buffer (0.1% formic acid and 10 mM ammonium formate), methanol, and acetonitrile (1:6:3, v/v/v). The analytes were monitored by tandem mass spectrometry in the multiple reaction monitoring method pro