Determination of hydralazine and metabolites in urine by liquid chromatography with electrochemical detection.

The cyclic voltammetric behavior of hydralazine and its primary metabolites, the pyruvate and acetone hydrazones, was examined in the positive potential range at both conventional and electrochemically pretreated glassy carbon electrodes. The enhanced oxidations observed at the treated surface were used as the basis of amperometric electrochemical detection of the compounds following reversed-phase liquid chromatography. The detection limits so obtained at +0.75 V vs. Ag/AgCl (1, 3, and 5 ng injected, respectively) were comparable to those previously reported for absorption and fluorescence detection approaches employing derivatization/preconcentration procedures. For liquid chromatography with electrochemical detection, however, direct quantitation of all three species in urine samples was readily accomplished without any chemical derivatization or sample treatment operations other than particulate filtration.