Analysis of thyreostatic drugs in thyroid samples by liquid chromatography tandem mass spectrometry: Comparison of two sample treatment strategies

A method based on ultra-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (UPLC-MS/MS) for the determination of six thyreostatic drugs in thyroid tissue has been optimised and validated in accordance with Decision 2002/657/EC. Sample extraction was evaluated in methanol and in ethyl acetate, the latter which gave better results. Two clean-up strategies were compared: one based on silica cartridges (SPE), and the other, on gel permeation chromatography (GPC). Recoveries ranged from 40% to 79% for the SPE approach and from 80% to 109% for GPC. Quantification was performed with blank tissue samples spiked with the analytes in the range 50-500 mu g kg(-1). 5,6-Dimethyl-2-thiouracil and 2-mercaptobenzimidazole-d(4) were used as internal standards. Decision limit (CC alpha) and detection capability (CC beta) ranged from 1 to 15 mu g kg(-1) and from 6 to 25 mu g kg(-1), respectively. The accuracy of the method was calculated as percent error, which was less than 10%. The relative standard deviation in reproducibility conditions ranged between 2% and 14%. (C) 2008 Elsevier B.V. All rights reserved.