Utility of Certain π-Acceptors for the Spectrophotometric Determination of Hydralazine Hydrochloride

The interaction of hydralazine hydrochloride with picric acid (I), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (II), 2,4-dinitrobenzoic acid (III), bromanil (IV) and chloranil (V) was found to be useful for its spectrophotometric determination. The determination was carried out at 520, 510, 550, 540 and 535 nm for the reaction with (I), (II), (III), (IV) and (V), respectively. The effect of several variables on the colouring process was studied. The proposed methods have been applied successfully for the determination of hydralazine hydrochloride in pure samples and in pharmaceutical preparations with good accuracy and precision. The results were compared to those obtained by the official and pharmacopoeia1 methods. The linear ranges for obedience of Beer's law are up to 118, 54,639, 27.5 and 78.6 mg/l, Ringbom ranges are 13-100, 7.6-44.7, 77.4-445.0, 5.8-25.8 and 22.5-63.1 μg/ml, Detection limits are 4.8, 2.2, 18.4, 1.2 and 5.9 mg/l, and RSD 0.042, 0.037, 0.043, 0.013 and 0.073 for reactions of hydralazine hydrochloride with I, II, III, IV and V, respectively.