[Determination of the thyreostats in animal muscle tissue by matrix solid-phase dispersion (MSPD) and liquid...

The residues ofthyreostats must not be present in the edible animal tissues. The proposed in the EU minimum required performance limit (MPRL) in the animal tissues is 10 microg/kg. This implies the decision limit (CCalpha) and decision capability (CCbeta) of the analytical methods used for the determination of these compounds lower than 10 microg/kg.

This study aimed at the development, basing on the literature data and own studies the analytical method allowing for the identification and quantification of five thyreostats: tapazole (TAP), thiouracil (TU), methylotiouracil (MTU), propylothiouracil (PTU) and phenylotiouracil (FTU)) in the bovine muscle tissue, which would meet the criteria set in the Commission Decision No 2002/657/EC.

The developed method used liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sample was extracted and cleaned using the matrix solid-phase dispersion (MSPD) method. The LC was equipped with column Luna C18 Phenomenex. Dimetylotiouracyl was used as internal standard. The samples were fortified at levels: 5, 10 and 20 microg/kg. The method was validated according to the criteria laid down in Commission Decision No. 2002/657/EC.

At the levels, mean relative recoveries was in the range 90 - 109% and repeatability (CV %) was less than 10%. Decision limit (CCalpha) and detection capability (CCbeta) calculated for all thyreostats were below the recommended minimum required performance limit (MRPL) - 10 microg/kg.

The developed and validated LC-ESI-MS/MS method allows for the identification and quantification of five thyreostats in the bovine muscle tissue in the quantities below 10 microg/kg. Analytical procedure meets the criteria of Commission Decision No 2002/657/EC.