ION-PAIR REVERSED-PHASE LIQUID-CHROMATOGRAPHIC DETERMINATION OF DIHYDRALAZINE

Dihydralazine, a vasodilator drug chemically related to the structural class of the hydrazinophthalazines, was used as a tracer to monitor ( water-oil-water) multiple emulsion stability. The hydrophilic characte r of the ionized form of dihydralazine hinders its chromatographic beh aviour by inducing a low retention with alkyl-grafted supports. In add ition, the two hydrazine functions induce some important interactions with the polar sites of the stationary phase. This yields highly taili ng and poorly retained peaks, hence there is a need to develop an ion- pair technique on a stationary phase recommended for the analysis of b asic drugs. After optimization, the optimum chromatogram was obtained with a C-8, RP-Select B column using a mobile phase consisting of a mi xture of methanol (50%) and an aqueous solution of phosphate (2.5.10(- 2) M) and sodium heptanesulfonate (2.5.10(-2) M) at pH 4.4. This metho d was found to be accurate and precise for a range of dihydralazine co ncentrations from 1 to 120 mu g/ml.