Analysis for procainamide and N-acetyl procainamide in plasma or serum by high-performance liquid chromatography

A high-performance liquid chromatography method is presented for simultaneous analysis for procainamide and N-acetyl procainamide in plasma or serum. The procedure involves internal-standard addition, organic extraction, and separation on a reverse-phase column. The detection limit for procainamide is 0.1 mg/liter and the calibration plot is linear to at least 30 mg/liter. Comparison with a colorimetric assay for procainamide gave a correlation coefficient of 0.989. We checked for interference by a large series of appropriate drugs, and found none, nor did icteric or lipemic sera present problems.