Abstract: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the occurrence of cortisone and cortisol in beef and milk marketed in some regions of China. Homogenized samples were digested in acetic acid-sodium acetate buffer, and extracted with methanol. Then, the extract was purified on graphitized carbon black (GCB) and amino (NH2) solid phase extraction (SPE) catrideges. The eluate was pooled and blown to dryness by N2, and the residue was redissoved in methanol-water mixture before being analyzed by LC-MS/MS. Data analysis was carried out using SPSS version 21.0. A total of 346 beef and milk samples from nine provinces and municipalities in China were analyzed by LC-MS/MS. Cortisone and cortisol were detected in both beef and milk with detection rates ranging from 86.1% to 100.0% at concentration levels of 0.02–74.88 μg/kg. The mean (median) contents of cortisone and hydrocortisone in beef were 1.69 (1.14) and 12.16 (8.14) μg/kg, respectively, and the mean (median) contents of cortisone and hydrocortisone in milk were 0.23 (0.23) and 0.72 (0.72) μg/kg, respectively. The contents of hydrocortisone and cortisone in beef and milk were significantly positively correlated with each other.

Key words: cortisone; cortisol; beef; milk