Determination of MRL regulated corticosteroids in liver from various species using ultra high performance liquid chromatography–tandem mass spectrometry (UHPLC)

Dexamethasone, betamethasone, prednisolone and methylprednisolone are corticosteroids widely used in animal husbandry. These compounds are licensed for therapy in veterinary practices while their use for growth promoting practices, mainly in combination with other growth promoters, is prohibited within the European Union. In order to protect the consumer, maximum residue limits (MRLs) have been set by the European Community in liver to 2.0 μg kg−1 (dexamethasone and betamethasone) and 10.0 μg kg−1 (prednisolone and methylprednisolone) for different species. The major challenges in the analysis of dexamethasone and betamethasone consist in performing an efficient separation of both isomers and in detecting and identifying all the molecules according to the regulatory requirements fixed in Commission Decision 2002/657/EC. In this context, an UHPLC–MS/MS method with a short runtime (7 min) and using the SRM acquisition mode was developed and validated. An efficient selectivity of the sample preparation combined with a high sensitivity of the measurement system allowed identifying and quantifying the four corticosteroids of interest in this complex biological matrix. Signals obtained were found very repeatable, even at very low concentration levels with an unambiguous identification of the compounds. The performance limits of the method have been validated according to the regulatory requirements and the method has been successfully applied to the confirmation of incurred liver samples.