Multiresidue analysis of glucocorticoids in milk by LC-MS/MS with low-temperature purification and dispersive solid-phase extraction.

A multiresidue method for the determination of 12 glucocorticoids (clobetasol propionate, budesonide, triamcinolone, triamcinolone acetonide, fludrocortisone acetate, flumethasone, beclomethasone, prednisone acetate, 6-α-methylprednisolone, hydrocortisone, cortisone, and prednisone) in bovine milk was developed using liquid chromatography with tandem mass spectrometry. Isoflupredone was used as an internal standard. Milk samples were treated with ethyl acetate to extract glucocorticoids and were frozen at -20°C for 6 h to precipitate fat. The extract was dried under nitrogen, and residues were dissolved in an acetonitrile/water solution. A further clean-up step was used by dispersive solid-phase extraction, with octadecyl silica and primary secondary amine as the absorbents. The recoveries of glucocorticoids spiked at 0.5, 1.0, 10.0 μg/kg ranged from 75.7 to 117.3%, except for clobetasol propionate and budesonide (16.1-49.5%). The limits of quantification were 0.01-0.5 μg/kg in milk. This method has been successfully applied in real samples. The results demonstrated that this method is simple, robust, and suitable for identification of glucocorticoid residues in milk.