Dihydralazine sulfate analysis using 2-methyl-o-nitropyridine-6-carboxaldehyde

A sensitive, selective colorimetric assay was developed for the quantitative analysis of dihydralazine sulfate. The method is based on the interaction of buffered (pH 4) dihydralazine sulfate with a methanolic solution of 2-methyl-3-nitropyridine-6-carboxaldehyde upon heating to give an orange color. This color can be quantified spectrophotometrically at 450 nm,with a lower limit of detection of 1 mug/ml. The color is stable for at least 24 hr. There is no interference from other drugs likely to be present along with dihydralazine sulfate and common excipients. The method was used successfully for the determination of dihydralazine sulfate in combination with other drugs in different commercial tablets. The developed method was applicable as a stability-indicating assay.