Valproic acid (VPA), a widely used antiepileptic drug, has a narrow therapeutic range of 50-100 μg/mL and shows large individual variability. It is very important to monitor the trough VPA concentration using a reliable method. The aim of this study was to develop and validate a rapid gas chromatographic (GC) technique for VPA quantification in human plasma and to compare it with the traditional immunoassay method. VPA extraction from human serum was efficient by dichloromethane and

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... acid using octanoic acid as an internal standard. GC analysis was performed using a gas-chromatograph equipped with a flame ionization detector (GC/FID). VPA detection and quantification were accomplished isothermally at 135°C on a Gs-BP 100% dimethylpolysiloxane capillary column (10 m×0.53 mm ID, 2.65 μm film thickness, Supelco, Bellefonte, PA). Injection port and detector temperature were 280°C. Retention times of VPA and internal standard were 1.83 min and 2.33 min, respectively. The calibration curve was linear over the concentration range of 5-320 μg/mL, with a lower limit of detection of 1.25 μg/mL. The internal and inter-day precision was less than 5.3% and 6.1%, respectively, and the accuracy was below 2.8%. VPA recovery was 94.6%. A quick and accurate method for VPA determination in human plasma was developed and validated. It resulted sufficiently selective and sensitive.