Trace determination of dexamethasone sodium phosphate in pharmaceutical formulations by differential pulse polarography

A simple and rapid differential pulse polarographic method has been developed for the trace determination of dexamethasone sodium phosphate. A well-defined single peak with an Ep value of –1.14 V is obtained in acetate buffer (pH 5.0). The linearity is valid in the range 0.2–1.2 mg/25 mL (r=0.9992) with minimum detection limit of 7.6×10–6 M. The precision of the method developed is implied from the values of relative mean deviation, standard deviation and coefficient of variation, which are 2.44%, 0.014 and 3.5% respectively. Marketed formulations of dexamethasone sodium phosphate have been analysed by calibration and standard addition methods. Recovery experiments were found to be quantitative, and analysis to determine the mass per tablet was obtained within ±0.2% of the expected market value. The studies have shown that the method is reproducible and accurate and can be used in the analysis of marketed formulations.