Determination of hydralazine metabolites: 4-hydrazino-phthalazin-1-one and n-acetylhydrazinophthalazin-1-one by gas chromatography and s-triazolo[3,4-alpha]phthalazine and phthalazinone by high-performance liquid chromatography.

Methods are described for the determination of 2-N-acetylhydrazinophthalazin-1-one, 4-hydrazinophthalazin-1-one, phthalazinone and s-triazolo[3,4-alpha]phthalazine in human urine. 4-Hydrazinophthalazin-1-one and 4-N-acetylhydrazinophthalazin-1-one (following acid hydrolysis) are reacted with acetylacetone to give a distinctive pyrazole derivative which can be determined by gas chromatography using a nitrogen-specific detector. Phthalazinone and s-triazolo[3,4-alpha]phthalazine are measured underivatised by high-performance liquid chromatography.