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Simultaneous determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion and gas chromatography-mass spectrometry.

Journal of chromatography. A (2005-06-09)
Lei Zhang, Yuan Liu, Meng-Xia Xie, Yue-Ming Qiu
ABSTRACT

A method for determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion (MSPD) and gas chromatography-mass spectrometry in selected ion detection mode was developed. Thyreostatic compounds in different matrices were extracted and purified by combination of MSPD and subsequent solid-phase extraction. Silica gel was selected as the solid support of both procedures and the conditions of the procedures were optimized. Thyreostats were derivatized with pentafluorobenzylbromide (PFBBr) in strong basic medium and then with N-methyl-N-(trimethylsilyl)-trifluoroacetamide (MSTFA), which can improve the yields of derivatization for thyreostats, the repeatability, and therefore the limits of detection (LOD) of thyreostats. The limits of detection reached 10 microg/kg (2-thiouracil, 6-methyl-2-thiouracil and 6-propyl-2-thiouracil), 20 microg/kg (6-phenyl-2-thiouracil) and 50 microg/kg (tapazole) with high recoveries (more than 70% for most of thyreostats) and relative standard deviations between 4.5% and 8.7%.

MATERIALS
Product Number
Brand
Product Description

Supelco
6-Methyl-2-thiouracil, VETRANAL®, analytical standard
Sigma-Aldrich
6-Methyl-2-thiouracil, purum, ≥98.0% S basis (elemental analysis)
Supelco
N-Methyl-N-(trimethylsilyl)trifluoroacetamide, BioReagent, for silylations, LiChropur
Sigma-Aldrich
6-Propyl-2-thiouracil, enzyme inhibitor
Sigma-Aldrich
6-Phenyl-2-thiouracil, ≥95%
Sigma-Aldrich
2,3,4,5,6-Pentafluorobenzyl bromide, 99%
Supelco
N-Methyl-N-(trimethylsilyl)trifluoroacetamide, synthesis grade
Supelco
N-Methyl-N-(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane, for GC derivatization, LiChropur
Supelco
N-Methyl-N-(trimethylsilyl)trifluoroacetamide, for GC derivatization, LiChropur, ≥98.5%