Assay for valproic acid and its E-Delta(2) metabolite in rat plasma by capillary gas chromatography without prior derivatization

A new and improved gas chromatographic assay method for valproic acid and a metabolite, E-Delta(2) valproic acid, in rat plasma has been developed. The assay has sufficient sensitivity to measure free levels of the parent drug and metabolite. By employing a Stabilwax-DA capillary column, symmetrical chromatographic peaks were obtained without the need for prior derivatization. Standard curves for valproic acid were linear from 0.1 to 640 mu g/ml. Standard curves for the metabolite were linear from 0.1 to 556 mu g/ml.