Determination of Thiabendazole, 5-Hydroxythiabendazole, Fenbendazole, and Oxfendazole in Milk

Abstract

The liquid chromatographic determination previously developed for benzimidazoles in cattle liver has been slightly modified and applied to the determination of 4 benzimidazoles in milk. Recoveries of fenbendazole (FBZ), oxfendazole (OFZ), and thiabendazole (TBZ) from milk fortified at the 10 ppb level were 80% or greater with an intralaboratory coefficient of variation of 11% or less. Recovery of 5-hydroxythiabendazole (5-OH-TBZ) at the 30 ppb level averaged 56% with an intralaboratory coefficient of variation of 5%. Limited data on the depletion of FBZ, OFZ, TBZ, and 5-OH-TBZ in milk were also generated.