COLORIMETRIC MICRODETERMINATION OF SOME CORTICOSTEROID DRUGS USING INDOPHENOL AS CHROMOPHORIC REAGENT

A simple, rapid and sensitive method for the determination of betameth asone (I), dexamethasone (II) and hydrocortisone (III), either in the pure form or in pharmaceutical formulations is described. Tile method is based on the development of a brown product with indophenol in basi c aqueous-ethanolic (50% v/v) medium. The optimum reaction conditions for the charge transfer complex formed were assessed. The absorbance m easurements were made at 820, 816 and 822 nn for I, II and III respect ively. The calibration graph was linear in the range 1-26, 1-32 and 1- 35 mu g/ml of I, II and III with slopes of 0.028, 0.021 and 0.024, res pectively. For more accurate analysis, Ringbom optimum concentration r anges were 2.5-23.0, 3.0-28.5 and 3.0-33.0 mu g/ml for I, II and III, respectively. The precision of the procedure was checked by calculatin g the relative standard deviation of ten replicate determinations on a sample containing 20 mu g/ml for each drug and was found to be 1.67, 1.39 and 1.85% for I, II and III, respectively. Many common excepience and common drugs present in their dosage forms do not interfere, and the tolerable levels were evaluated. Results of analysis of pure drugs and their dosage forms by the proposed method are in good agreement w ith those of the British Pharmacopoeia 1993 procedure.