Determination of Ethosuximide in Plasma By Derivatization and High Performance Liquid Chromatography

Abstract

A simple and sensitive liquid chromatographic method is described for the determination of ethosuximide in plasma as a highly sensitive derivative. Ethosuximide in plasma, after separation with isopropanol extraction, was derivatized with strong chromophore reagent, 4-bromomethyl-7-methoxy-coumarin. The resulting derivatives were separated on a Nova-Pak C18 column with water-acetonitrile-methanol(60:20:20, v/v) as the mobile phase. The linear range for the determination of ethosuximide in spiked plasma was over 2-40 nmol. The limit of detection for ethosuximide was about 7.0 ± 1.2 pmol per 20 μL injection (S/N= 5). The intraday relative standard deviation (n = 6) and the interday relative standard deviation (n = 12) were all less than 2.5% for ethosuximide. The recovery for ethosuximide in plasma was greater than 96%.