Determination of hydralazine in human whole blood

The time required for the separation of plasma from the cellular components of blood can permit the in vitro loss of hydralazine. Thus, a high-performance liquid chromatographic (HPLC) procedure for the measurement of hydralazine in blood has been developed. 4-Methylhydralazine was used as an internal standard. The addition of p-anisaldehyde led to the formation of the p-anisaldehyde hydrazones of hydralazine and the internal standard. HPLC on a reverse-phase cyano column provided an analytical procedure in which the average relative standard deviation over the concentration range of 1-160 ng/ml was 8.3%. Hydralazine pyruvic acid hydrazone, a known circulating metabolite of hydralazine, yielded only 0.05 mole % hydralazine when submitted to this assay procedure.