Extraction-Spectrophotometric Method for the Determination of Betamethasone in Pure Form and in Pharmaceutical Formulations

ABSTRACT

A sensitive and rapid extraction-spectrophotometric method for the determination of betamethasone, based on the formation of a charge transfer complex with benzocaprol red (I) and acid ethyl blue (II) is described. The calibration graph, resulting from the measurement of the absorbance of the chloroform and benzene extracts (10 ml) at 588 and 677 nm using I and II. respectively, is linear over the range 0–16 and 0–20 μg ml⁻¹ of betamethasone with relative standard deviations (R.S.D.) of 1.6 and 1.3% for 5 μg ml⁻¹ betamethasone using reagents I and II, respectively. For more accurate results. Ringbom optimum concentration ranges were found to be 2–14 and 2–17.5 μg ml⁻¹ using reagents 1 and II, respectively. The method was satisfactorily applied to the determination of betamethasone and its esters in pharmaceutical preparations and found in good agreement with the British Pharmacopeia (1993) method.

Keywords:

• Chromotropic acid azo dyes
• betamethasone determination
• extraction, spectrophotometry.