On-column propylation method for measuring plasma valproate concentration by gas chromatography.

A gas-chromatographic method is described for measuring plasma valproate concentrations. This method incorporates double-solvent extraction of the plasma sample and on-column propylation of valproic acid and 2-propylhexanoic acid, used as the internal standard. The identity of the propyl ester derivatives of these compounds was confirmed by gas chromatography-mass spectrometry. The accuracy and simplicity of the method make it suitable for routine laboratory use. The assay is sufficiently rapid that a plasma sample can be analyzed in duplicate within 30 min.