LC-ESI-MS method for the determination of dexamethasone acetate in skin of nude mouse

A high-performance liquid chromatography-positive electrospray ionization single quadrupole mass spectrometric (LC-ESI-MS) method for the determination of dexamethasone acetate in skin of nude mouse using triamcinolone acetonide acetate as the internal standard (I.S.) was developed and fully validated. Both compounds were precipitated from skin homogenate with methanol and were separated by HPLC on a Shimadzu Shim-pack VP-ODS C18 column (150mm×2.0mm, 5μm) with a mobile phase of methanol-water (80:20, v/v) at a flow rate of 0.2mL/min. Calibration curves were linear over the range of 0.05-5μg/mL. The intra-run relative standard deviations were less than 9.59%. The inter-run relative standard deviations were less than 7.82%. The mean recovery was in the ranges of 89.95-95.97%, respectively. The method was successfully applied to determinate the concentration of dexamethasone acetate in skin and study the percutaneous absorption process in skin of nude mouse.