Determination of cadralazine in human whole blood using reversed-phase high-performance liquid chromatography: utilizing a salting-out extraction procedure

A rapid, selective, and sensitive ion-paired reversed-phase high-performance liquid chromatographic method for determination of the new carbazate type of antihypertensive vasodilator agent cadralazine in human whole blood has been developed. Cadralazine was extracted from whole blood by adding 0.5 ml of acetonitrile to 1.0 ml of whole blood followed by salting-out of acetonitrile by the addition of potassium carbonate in excess. An aliquot of the salted-out acetonitrile was injected into the chromatographic system. A column packed with 3-microns octyl (C8) particles was used with an isocratic elution of 1% acetic acid and 5 mM hexanesulfonic acid-acetonitrile (70:30, v/v). The cadralazine was measured using ultraviolet detection at 250 nm and the assay was completed in less than 20 min and had a limit of quantitation of 10 ng/ml for a 100-microliters injection volume.