Determination of thyreostats in muscle and thyroid tissues by QuEChERS extraction and ultra-performance liquid chromatography tandem mass spectrometry

Abstract

The use of thyreostats as veterinary drugs is banned in the European Union since 1981 because of their carcinogenic and teratogenic properties. Controlling their illegal use in breeding animals is quite difficult because of their low molecular weight, high polarity and the presence of tautomeric forms. To harmonise the performance of analytical methods, the recommended concentration for thyreostats such as thiouracil, methylthiouracil, propylthiouracil and tapazole established by the Community Reference Laboratory in 2007 is 10 ng g⁻¹. The majority of the currently available analytical methods require a time-consuming derivatisation step and/or an SPE clean-up step. In this study, a rapid confirmatory method for the determination of six thyreostatic drugs – thiouracil, methylthiouracil, propylthiouracil, phenylthiouracil, tapazole and 2-mercaptobenzoimidazole – in thyroid and muscle at recommended concentration is presented. Quick sample extraction has been achieved by QuEChERS with ethyl acetate without further clean-up or derivatisation steps. Analysis has been carried out by using UPLC-ESI-MS/MS. Performance characteristics of the method have been determined in agreement with Commission Decision 2002/657/EC requirements for confirmatory methods and calculated decision limits (CCα) are below the recommended concentration (10 ng g⁻¹).

Keywords:

• thyreostats
• thiouracil
• LC-MS/MS
• QuEChERS