Simultaneous determination of valproic acid and its main metabolite in human plasma using a small scale dispersive liquid–liquid microextraction followed by gas chromatography–flame ionization detection

Abstract

A simple, sensitive, and rapid analytical method has been developed and validated for the extraction and quantification of valproic acid and its main metabolite (3-heptanone) in human plasma. Initially, the proteins of plasma were precipitated with trifluoroacetic acid. Then a very small volume of a water-immiscible extractant and acetonitrile was mixed and rapidly injected into the pre-treated plasma sample. For further turbidity (dispersion of the extractant into sample solution), the cloudy solution was vortexed. After centrifugation, the settled phase was injected into gas chromatography-flame ionization detection. The effective parameters, such as type and volume of extraction and disperser solvents, vortex time, and pH were studied and optimized. The limits of detection of valproic acid and 3-heptanone were obtained, 0.065 and 0.015 mg L−1, respectively. An acceptable precision was obtained for a concentration of 2 mg L−1 of each analyte (relative standard deviation ≤ 8%). The average absolute recoveries (n = 3) of valproic acid and 3-heptanone were 52 ± 2 and 42 ± 1%, respectively. The validated method has been successfully used in analysis of the analytes in human plasma samples.