A method for the determination of nine corticosteroids in bovine liver was developed. The liquid-liquid extraction method consisted in the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract was evaporated to dryness and the residue redissolved in acetonitrile. The removal of fats was performed with n-hexane and the acetonitrile layer was evaporated. Afterwards, analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as reagent. The recovery curves, performed at five spiking levels (different for each corticosteroid), showed that recoveries of at least 70.5% could be obtained from liver. The chemiluminescence detection gave satisfactory results with respect to sensitivity, and the LOQ ranged from 0.13 ppb for prednisolone to 8.40 ppb for betamethasone. The maximum mean RSD was 4.8% and 7.3% for intra- and inter-day assay, respectively.
A new method for the determination of dexamethasone (9alpha-fluoro-11beta,17alpha,21-trihydroxy-16alpha -methylpregna-1, 4-diene-3,20-dione) in bovine liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract is evaporated to dryness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysis of the extracts is performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as CL reagent. A series of recovery curves performed at spiking levels of 50, 30, 10, 5, and 2.5 ppb show that at least 80% of DEX can be recovered from liver and that the chemiluminescence detection yields satisfactory results with respect to sensitivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6.2-8.9).
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