[Determination of Flubendazole and Metabolite in Livestock Products Using LC-MS/MS]

This study proposes a method to determine flubendazole and metabolite R35475 in livestock products using tandem mass spectrometry coupled with positive ion electrospray ionization. Acetone is used to extract flubendazole and metabolite R35475 from the livestock samples. These extracts were purified using an SCX cartridge column (500 mg). Furthermore, high-performance liquid chromatography was performed on an Inertsil ODS-4 column with a gradient formed using methanol and water, both of which contain 5 mmol/L of ammonium acetate. The recovery tests using bovine muscle, fat, liver, milk, and egg fortified at the maximum residue limits of analytes or 0.005 mg/kg revealed that the trueness (n=5) of flubendazole and metabolite R35475 ranged from 89.4 to 106.4% with a repeatability rate of 1.7-7.8%.