Determination of dexamethasone in bovine liver by chemiluminescence high-performance liquid chromatography

A new method for the determination of dexamethasone (9 alpha-fluoro-11 beta ,17 alpha,21-trihydroxy-16 alpha-methylpregna-1,4-diene-3,20-dione) in bovi ne liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extractio n with ethyl acetate. After centrifugation, the extract is evaporated to dr yness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysi s 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 p pb show that at least 80% of DEX can be recovered from liver and that the c hemiluminescence detection yields satisfactory results with respect to sens itivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6. 2-8.9).