QUANTIFICATION OF PHENOBARBITAL IN HUMAN PLASMA BY LC/MS/MS FOR THERAPEUTIC DRUG MONITORING

A simple and sensitive LC/MS/MS method for quantification of phenobarbital and in human plasma has been developed and validated. Phenobarbital was separated under isocratic conditions using a mobile phase of 70:30 (v/v) 0.1% acetic acid and acetonitrile. In these chromatographic conditions, the retention time of phenobarbital was 1.2 min and the overall time of one analysis was 1.7 min. Plasma sample preparation consisted in protein precipitation with methanol. The detection of phenobarbital was realized in MRM mode using an ion trap mass spectrometer with electrospray negative ionization. The linearity domain was established between 2.00 and 80.00 mu g/mL. Accuracy (bias%) and precision (CV%) were less than 9.8% for intra-day assay and 12.6% for inter-day assay. The recovery ranged between 95.9 and 136.4%. The method is very simple and fast and was used for therapeutic drug monitoring of phenobarbital.