Investigation of residues of glucocorticoid drugs in cow milk in Ankara province

Glucocorticoids are a class of steroid hormones, produced by the adrenal cortex, that affect metabolism and have immunosuppressive and anti-inflammatory properties. Synthetic glucocorticoids are commonly used in farm animals to treat inflammatory diseases, musculoskeletal disorders and other diseases common in farm animals, as well as to improve feed intake and promote growth in farm animals. Abuse of glucocorticoid veterinary drugs in dairy industry can potentially threat milk safety and consequently influence human health. Long-term exposure to glucocorticoids may cause osteoporosis, myopathy, growth suppression, hyperglycemia, hypertension, coronary heart disease, hair loss, skin atrophy, cataract and neuropsychiatric symptoms in humans. Dexamethasone, betamethasone, prednisolone and methylprednisolone are glucocorticoids permitted for therapeutic use in farm animals. Maximum Residue Levels in milk intended for human consumption have been established by the Ministry of Agriculture and Forestry in accordance with European Union Commission regulations. The MRLs set in milk are 0.3 µg/kg for betamethasone and dexamethasone, 6 µg/kg for prednisolone and 2 µg/kg for methylprednisolone. In this study, 600 samples, including UHT milk (n=200), pasteurized milk (n=200), and raw milk (n=200) were collected to investigate the glucocorticoid drug residue status in commercial and raw milk in Ankara province. Milk samples were analyzed for the presence of any of the glucocorticoids with MRL using a screening method combined with high-performance liquid chromatography analysis with a method time of 4 min. Confirmatory analyses of samples containing glucocorticoids residues were performed by liquid chromatography tandem mass spectrometry. Among the three extraction methods applied for the determination of glucocorticoids, solid-phase extraction with the highest recovery was selected as the extraction method for the study and was validated according to the 2021/808 EC guideline. The screening and confirmation methods showed a linearity ≥0,996, recoveries within the range 94.2–101.7%, precision expressed as CV ≤13.9%. For the study, UHT and pasteurized milk samples were collected from local markets and raw milk samples were collected from milk-producing farms. No residues of the relevant compounds were found in the UHT and pasteurized milk samples analyzed, Prednisolone was detected at a concentration of 4.18 ug/kg in one raw milk sample, below the regulated MRL.