Detection of synthetic corticosteroids in bovine urine by chemiluminescence high-performance liquid chromatography.

The development of a black market of chemical cocktails for illegal growth promotion in food-producing animals includes substances that are potentially dangerous for human health, such as synthetic corticosteroids. The potential presence of these residues in food makes it necessary to develop rapid and sensitive analytical methodologies to detect such substances, preferably in live animals before they arrive at the market. A chemiluminescence (CL) detection method for the determination of four synthetic corticosteroids (prednisolone, betamethasone, dexamethasone and flumethasone) in bovine urine has been developed. The proposed system, which does not need any derivatization procedure, offers an easy method well suited for routine research. Urine samples were homogenized with methanol:water (50:50, v/v) and centrifuged. The upper layer was collected and Strata X cartridges were used for cleaning up. The purified residues were evaporated to dryness and then redissolved in the mobile phase. Analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection, employing luminol as the CL reagent. The recovery curves, obtained at four spiking levels (different for each corticosteroid), showed that recoveries of at least 70% could be obtained for urine. The chemiluminescence detection procedure afforded satisfactory results with respect to sensitivity and the LOD and LOQ, taken as the first point of the regression curve, ranged from 4 ppb to 65 ppb. The maximum mean RSD was below 13% and below 15% for intra- and inter-day assay, respectively, in all cases.