Determination of flunixin and tiamulin hydrogen fumarate in meat and toltrazuril and the metabolite toltrazurilsulfon in meat and eggs using LC/MS

A liquid chromatographic-atmospheric pressure ionization ion spray method is described for the determination of flunixin (FLU), tiamulin hydrogen fumarate (TIA) in meat, and toltrazuril (TOL) and the metabolite toltrazurilsulfon (TOLS) (Ponazuril) in meat and egg. The method can also be used for the determination of flunixin in milk. Samples were extracted with acetone-tetrahydrofurane, after which the organic layer was separated from water with dichloromethane and evaporated to dryness. The dry residue was diluted in methanol-l-heptane sulfonic acid and fat was extracted with hexane, filtered, and injected into the LC-MS. The lower limit of quantification for flunixin and toltrazuril were 5 ng/g and for tiamulin and toltrazurilsulfon in meat 2 ng/g.