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 μg kg−1. 5,6-Dimethyl-2-thiouracil and 2-mercaptobenzimidazole-d4 were used as internal standards. Decision limit (CCα) and detection capability (CCβ) ranged from 1 to 15 μg kg−1 and from 6 to 25 μg 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%.