Simultaneous Determination of Ethosuximide, Phenobarbital, Pheny-Toin, and Carbamazepine in Brain Tissue by HPLC

Abstract

A simple and rapid method was evaluated for the simultaneous determination in brain tissue of ethosu-ximide, phenobarbital, phenytoin, and carbamazepine. The drugs were simultaneously extracted at low pH using dichloromethane as extraction solvent in the presence of an excess of ammonium sulfate. High-performance liquid chromatography was performed on a Sphe-risorb 50DS column, with a mobile phase of acetoni-trile/methanol/phosphate buffer pH 4.0 (21:24: 55 by vol), and monitored at 195 nm. The internal standard was 5-(p-tolyl)-5-phenylhydantoin. The sensitivity, precision, and reproducibility of the assay were all found to be acceptable for the simultaneous determination of the above described drugs in small samples of brain tissue.