FLOW-INJECTION CHEMILUMINOMETRIC DETERMINATION OF STEROIDS

A rapid, accurate, precise and fully automated flow-injection method i s described for the determination of 0.02-0.50 mu g ml(-1) cortisone, 0.02-1.00 mu g ml(-1) hydrocortisone and 0.20-5.00 mu g ml(-1) dexamet hasone in aqueous solutions and of 1.0-20.0 mu g ml(-1) prednisolone, methylprednisolone, progesterone, corticosterone and testosterone and 2.0-20.0 mu g ml(-1) betamethasone in 20% (v/v) acetonitrile solutions . The method is based on the sensitizing effect of each steroid on the chemiluminogenic cerium(IV)-sulphite reaction. Limits of detection ar e in the ranges 0.013-0.019 and 0.05-4.00 mu g ml(-1) for aqueous and acetonitrile solutions, respectively. Common excipients do not interfe re greatly and the mean recovery of steroids from commercial formulati ons was 102.6% (range 94.2-109.0%). The method allows the measurement of up to 100 samples per hour and can be used for content uniformity t ests and the results were in good agreement with the official method f or commercial formulations with a relative error < 4%.