DETERMINATION OF BETAMETHASONE AND DEXAMETHASONE IN PLASMA BY FLUOROGENIC DERIVATIZATION AND LIQUID-CHROMATOGRAPHY

A simple and sensitive liquid chromatographic method is described for the determination of betamethasone and dexamethasone in plasma as fluorogenic derivatives. Betamethasone or dexamethasone in plasma after separation with a Sep-Pak C-18 cartridge was derivatized with 1-ethoxy-4-(dichloro-s-triazinyl)naphtha. The resulting derivatives were separated on a reversed-phase C-18 column with acetonitrile-water (60:40, v/v) as the mobile phase. The linear range for the determination of each glucocorticoid in spiked plasma was over 2.5-50.0 pmol. The limit of detection for betamethasone or dexamethasone was 80.0 fmol per 20 mu l injection (S/N = 5). The intraday relative standard deviations (n = 5) and the interday relative standard deviations (n = 3) were all less than 11% for both glucocorticoids. Recoveries for both glucocorticoids were greater than 90%.