An improved method for preparation of samples for the simultaneous assay of some antiepileptic drugs by gas-liquid chromatography.

A new simple extraction method, e.g., for subsequent quantitative determination of some antiepileptic drugs by GLC is described. HCl and an internal standard are added to 100 microliter of plasma or any biological fluid. This mixture is applied directly to an Extrelut column. Lipophilic substances (i.e. the antiepileptic drugs diphenylhydantoin, primidone and phenobarbital) are then extracted into 20 ml of ether and the solvent is evaporated to dryness. Direct GLC analysis of the on-column methylated drugs is performed using a P-N-detector.