Determination of valproic acid (dipropylacetic acid) in plasma by gas-liquid chromatography.

A specific and sensitive procedure for the determination of valproic acid at therapeutic concentrations in human plasma has been developed. The method involves a microscale extraction of the drug from acidified plasma into chloroform. Caproic acid is added as internal standard. The extract is subsequently analysed on a gas chromatography fitted with a flame ionisation detector, and quantitation achieved by the relative-peak-height technique.