Solvent Flush Method for Determination of Valproic Acid in Plasma by Gas Chromatography

A simple method for the determination of valproic acid (VPA) by gas chromatography, which can be applied to the direct analysis of VPA in plasma without extraction, was developed. The method, the solvent flush method, requires only 1μl of the plasma. The plasma sample was sandwiched by phosphoric acid phases, and directly injected into the gas chromatograph. The detection limit concentration of VPA using 1μl of plasma was ca. 5μg/ml.This method made it possible to determine VPA rapidly and easily, since a few microliters of blood can easily be collected into a capillary tube and only a brief centrifugation is then required before the assay. Thus, physical damage to samll animals, such as rats, caused by frequent blood collection is minimal.