thiouracil and 2-mercaptobenzimidazole

Two multivariate calibration methods, partial least squares (PLS) and principal component regression (PCR), were applied to the spectrophotometric simultaneous determination of 2-mercaptobenzimidazole (MB) and 2-thiouracil (TU). A genetic algorithm (GA) using partial least squares was successfully utilized as a variable selection method. The concentration model was based on the absorption spectra in the range of 200 to 350 nm for 25 different mixtures of MB and TU. The calibration curve was linear across the concentration range of 1 to 10 microg mL(-1) and 1.5 to 15 microg mL(-1) for MB and TU, respectively. The values of the root mean squares error of prediction (RMSEP) were 0.3984, 0.1066, and 0.0713 for MB and 0.2010, 0.1667, and 0.1115 for TU, which were obtained using PCR, PLS, and GA-PLS, respectively. Finally, the practical applicability of the GA-PLS method was effectively evaluated by the concurrent detection of both analytes in animal tissues. It should also be mentioned that the proposed method is a simple and rapid way that requires no preliminary separation steps and can be used easily for the analysis of these compounds, especially in quality control laboratories.

Topics: Animals; Benzimidazoles; Calibration; Cattle; Chemistry Techniques, Analytical; Least-Squares Analysis; Multivariate Analysis; Principal Component Analysis; Sheep; Spectrophotometry; Thiouracil

A novel approach for determination of 2-mercaptobenzimidazole (MBI) and other thyreostatic residues in animal tissues by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring mode was developed. The analytes in animal tissues (including hypothyroid, pork muscle and beef samples) were extracted by acetonitrile, and then purified by a matrix solid-phase dispersion (MSPD) procedure after the extraction residues had been dissolved in water. The thyreostatic residues were derivatized by pentafluorobenzyl bromide (PFBBr) under strong basic conditions and then N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) before GC/MS analysis. Different kinds of solid supports with various polarities for the MSPD procedure were investigated, and it was found that silica gel was suitable for the purpose. The average recoveries of the thyreostatic drugs in animal tissues ranged from 71.5-96.9% with the relative standard deviations below 10%. By using the developed method, the limits of detection were 10 microg/kg for MBI; 5 microg/kg for 6-phenyl-2-thiouracil; and 2 microg/kg for 2-thiouracil, 6-methyl-2-thiouracil and 6-propyl-2-thiouracil. The stability of the thyreostatic drugs in spiked animal tissues was tested, and the results showed that the thyreostatic drugs did not decompose within 3 months if the sample was stored in darkness below -20 degrees C.

Topics: Animals; Antithyroid Agents; Benzimidazoles; Cattle; Drug Residues; Food Contamination; Gas Chromatography-Mass Spectrometry; Hypothyroidism; Meat; Spectrometry, Mass, Electrospray Ionization; Swine; Thiouracil