An improved gas liquid chromatographic assay for plasma valproic acid concentrations in mentally handicapped epileptic children.

A gas liquid chromatographic (GLC) method is described for the determination of valproic acid concentrations in plasma. This simple, rapid and reproducible assay involved chloroform (500 microliter) extraction of the drug and internal standard (octanoic acid) from acidified plasma samples. An aliquot (1 microliter) of the unconcentrated organic extract was injected directly into the GLC system (a coiled glass column 1 m long, 6 mm OD packed with 5% diethylene-glycol-succinate-phosphate on 100/120 mesh Supelcoport) with detection by flame-ionization. This assay was successfully employed to measure plasma concentrations of valproic acid in 42 mentally handicapped, epileptic children of Chinese origin, most of whom were on multiple anti-epileptic agents.