Quantitative Determination of Methohexital in Human Whole Blood by Liquid Chromatography Tandem Mass Spectrometry

A rapid, simple and sensitive liquid chromatography tandem mass spectrometry method for the determination of methohexital in human whole blood was developed and validated. Ethyl acetate/n-hexane (9:1) was used as extraction solvent while aprobarbital was used as internal standard. Methohexital was recovered by liquid-liquid extraction from 100 μL of human whole blood. The mobile phase was water-acetonitrile, and an ACQUITY BEH C18 (2.1 × 100 mm, 1.7 μm) column was adopted. Negative electrospray ionization source and multiply reaction monitoring mode were applied. The transitions of m/z were 261.2/42.2 and 261.2/119.0 for methohexital. The limit of detection was 0.5 ng/mL, which was lower than the previous methods. Wide linear range (2-2,000 ng/mL) with a good correlation coefficient (r > 0.99) was also obtained. The intra- and inter- day precisions represented by relative standard deviation were <11.5%, and the recoveries were >79.67%. This analytical method involved small sample volume and had been proven to be rapid, easy, sensitive and specific. Therefore, it could be used for the clinical analysis of methohexital.