The determination of hydralazine in plasma by gas-liquid chromatography

A description is given of a gas chromatographic method for the determination of hydralazine in plasma. On treatment with nitrous acid, hydralazine is converted into tetrazolo[1,5-a]phthalazine, a stable compound that can be extracted from biological material with organic solvent and determined quantitiatively by gas-liquid chromatography. The 4-methyl analogue of hydralazine serves as internal standard for derivatization, extraction and gas chromatography. The sensitivity (10 ng per ml of plasma) is sufficient to monitor plasma levels in man after administration of single oral doses of 50 mg of Apresoline¿. The known metabolites do not interfere.