Determination of benzimidazole residues using liquid chromatography and tandem mass spectrometry.

The determination of residues of benzimidazole using liquid chromatography and tandem mass spectrometry (LC-MS-MS) with ion spray ionization is described. Swine muscle tissue was spiked with a mixture of fifteen benzimidazoles, including metabolites of fenbendazole and albendazole. As clean-up procedure, an ethyl acetate extraction followed by solid-phase extraction on styrol-divinyl-benzene cartridge was used. The evaluation was performed by selecting the characteristic product ions for the benzimidazoles and using multiple reaction mode. 2-n-Butylmercaptobenzimidazole was used as internal standard. Blank muscle samples were fortified in the concentration range of 1-22 microg/kg. The limits of detection were below 6 microg/kg and the limits of quantification for most benzimidazoles were below 10 microg/kg. The matrix effect was checked using spiked muscle tissues of cattle and sheep as well as liver of cattle. Practical application will be shown by incurred egg material from laying hens treated with flubendazole. The recovery of the clean-up was mostly above 50% in muscle tissue and 70% in egg yolk.