Development of a liquid chromatography-tandem mass spectrometry with pressurized liquid extraction for determination of glucocorticoid residues in edible tissues

A multi-residues method using pressurized liquid extraction (PLE) and liquid chromatography combined with mass spectrometry (LC-MS/MS) has been developed for determination of eight glucocorticoids (prednisone, prednisolone, hydrocortisone, methylprednisolone, dexamethasone, betamethasone, beclomethasone, fludrocortisone) in muscle of swine, cattle, and sheep. Parameters affecting PLE extraction including extraction solvent, extraction temperature, extraction pressure and extraction cycles were optimized. The optimized method employed 11 ml extraction cells, hexane-ethyl acetate (50:50, v/v) as extraction solvent, 1500 psi of extraction pressure and 50 degrees C of extraction temperature. The samples were detected by LC-ESI-MS/MS in negative mode with selected reaction monitoring (SRM) mode. The recovery of glucocorticoids spiked at levels of 0.5-6 mu g kg(-1) ranged from 70.1% to 103.1%; the between-day relative standard deviations were no more than 9.6%. The limits of quantification were 0.5-2 mu g kg(-1) in muscle. The results demonstrated that the method is simple, fast, robust, and suitable for identification and quantification of glucocorticoids residues in foods of animal origin. (C) 2010 Elsevier B.V. All rights reserved.