A Routine HPLC Method for Monitoring Midazolam in Serum

A routine high-performance liquid chromatographic method for measuring midazolam in human serum has been developed. The sample preparation procedure consisted of simple liquid–liquid extraction with dichloromethane, followed by evaporation under nitrogen. The mobile phase used was a mixture of acetonitrile at 0.02 M and sodium acetate at pH 3.0 (80:20, v/v) and a flow-rate of 1.2 mL/min. The separation was performed on two cyanopropyl columns (150×4.6 mm). The detection was by UV absorption at 240 nm. A linear range from 10 to 1000 ng/mL and a quantification limit of 7.4 ng/mL of serum was reached. The mean intra-assay and inter-assay reproducibility from serum sample spiked with 100 ng/mL were 4.1 and 4.7%, respectively. The recoveries from serum sample spiked with 50, 100, 500 ng/mL were 85.46, 85.38 and 85.57%, respectively. This method was developed to allow pharmacokinetic study of midazolam in young patients in short surgical interventions. © 1997 by John Wiley & Sons, Ltd.