Spectrophotometric determination of desoximetasone in ointment using 1,4-dihydrazinophthalazine

The proposed method is based on coloured hydrazone formation with 1,4-dihydrazinophthalazine as a reagent. Heating at 85 degrees C for 2 h was found necessary to ensure optimal hydrazone formation in the presence of hydrochloric acid. The yellow hydrazone product has an absorption maximum at 380 nm. A linear relationship between absorbance and concentration was established in the concentration range 3.19 x 10(-6) -3.19 x 10(-5) mol l-1 (the regression equation was y = 0.013 167 3 + 0.019 025 9x; correlation coefficient r = 0.9991; n = 6). The detection limit was 1.2 micrograms ml-1 (molar absorptivity found was 1.97 x 10(4) l mol-1 cm-1). The reliability of the proposed method was checked at three different concentrations; the relative standard deviation (RSD) varied from 1.03 to 2.01%. The described method applied to the determination of desoximetasone in ointment gave precise and reproducible results; the recovery was 98.55% with RSD = 2.40% (n = 10).