Determination of flumethasone in calf urine and serum by liquid chromatography–tandem mass spectrometry

Corticosteroids can be illegally administered to cattle as growth promoting agents to improve meat production. We developed a liquid chromatography–atmospheric pressure ionization mass spectrometry–mass spectrometry (LC–MS–MS) method able to identify and quantify flumethasone, one of the most potent fluorinated synthetic corticosteroid, in serum and urine from treated calves. The analyte was purified from urine (conjugated and free, following enzymatic hydrolysis) and from serum by C18 solid-phase and liquid–liquid extractions, then analyzed by LC–MS–MS monitoring the product ions of an abundant precursor (SRM in negative ionization mode). Results on flumethasone residues in biological fluids in three calves treated at different levels are presented. This method allowed the detection of flumethasone in bovine urine and serum at the 30-pg/ml level.