Analysis of thyreostatic drugs in thyroid samples by ultra-performance liquid chromatography tandem mass spectrometry detection

A method based on ultra-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry for the determination of six thyreostatic drugs in thyroid tissue has been optimised and validated in accordance with the Decision 2002/657/EC. Samples are extracted with methanol and the extracts cleaned-up on silica cartridges. The recoveries range from 40% for 6-phenyl-2-thiouracil to 79% for 2-thiouracil. Quantification is carried out with blank tissue samples spiked with the analytes in the range 25-500 microg kg(-1). 5,6-Dimethyl-2-thiouracil is used as internal standard. CCalpha and CCbeta are in the ranges 4.3-16.1 microg kg(-1) and 8.7-20.7 microg kg(-1), respectively. Accuracy, expressed as percentage of error, is lower than 6% and relative standard deviation in reproducibility conditions falls between 5.6 and 10.3%. Nowadays, the proposed method is routinely implemented in the laboratory of the Agència de Salut Pública de Barcelona and allows processing of up to 20 samples per day.