Determination of mercaptobenzimidazol and other thyreostat residues in thyroid tissue and meat using high-performance liquid chromatography-mass spectrometry.

This paper describes a method for extraction of tapazol, thiouracil, methylthiouracil, propylthiouracil and mercaptobenzimidazol (MBI) from thyroid tissue. The solid-phase extraction procedure is optimized to obtain the maximum results for the main thyreostats including MBI. Different combinations of sample application, column conditioning and wash steps were tested. The analytes were extracted from the matrix with methanol. After solid-phase extraction they were derivatised with 7-chloro-4-nitrobenzo-2-furazan. Determination is carried out using liquid chromatography-electrospray mass spectrometry. The identification of the analytes was performed according to the final revision of the EU criteria (93/256/EC decision). The detection capability was 20 microg kg(-1) for all mentioned thyreostats.