Assay for hydralazine as its stable p-nitrobenzaldehyde hydrazone.

A new method of analysis for the antihypertensive drug, hydralazine, is introduced. The assay involves the addition of p-nitrobenzaldehyde to blood samples containing hydralazine, to form a stable Schiff's base, hydralazine p-nitrobenzaldehyde hydrazone. The derivative is extracted from the blood into hexane and the samples are dried under a nitrogen stream. The extracts are then dissolved in mobile phase and analyzed using high-performance liquid chromatography. The extracted samples can be stored for at least 7 days at room temperature or at -20 degrees C. The sensitivity of the assay is better than 300 pg/ml using 3-ml blood samples, and the range can extend to 640 ng/ml. The stability of the extracted samples plus the sensitivity and simplicity of the assay are the main advantages of the method over other selective methods for hydralazine.