Determination of phenytoin in human plasma by gas chromatography

A gas chromatographic method for the determination of phenytoin in plasma is described. This assay allows the determination of phenytoin for therapeutic drug monitoring with a minimum detectable limit of 200 ngmL-1 for 500 mL plasma. Separation was performed on 2 m x 2 mm i.d. 1.5% OV17, 1.95 OV210 packed column using a flame-ionization detector. Barbital and tetramethyl ammonium hydroxide were used as internal standard and derivatizing agent, respectively. This method is simple, rapid and suitable for routine analysis of phenytoin in plasma.