Simultaneous gas chromatographic analysis for the four commonly used antiepileptic drugs in serum

We describe a simple, sensitive method for the determination of phenobarbital, diphenylhydantoin, carbamazepine and primidone in serum, by use of gas-liquid chromatography with temperature programming. The methylated derivatives of these anticonvulsants were well resolved, as was 5-(p-methylphenyl)-5-phenylhydantoin, the internal standard. In this procedure we used an ion-exchange resin for separation of the drug from the serum. The proposed procedure requires only 1.0 ml of serum and can be done in less than 1 h. The lower limit of detection for each of the drugs is 0.5 mg/1. Analytical recoveries of drug from serum were excellent and peak height and concentration were linearly related up to twice the toxic concentration for serum.