Application of a novel ultra-low elution volume 96-well solid-phase extraction method to the LC/MS/MS determination of simvastatin and simvastatin acid in human plasma

A novel extraction method has been utilized in the LC/MS/MS determination of simvastatin and simvastatin acid in human plasma. In this method, 300 μl of plasma sample was loaded onto a Waters Oasis 96-well HLB μElution plate, the stationary phase was washed using 2 × 400 μl of 5% methanol in water, and the analytes were eluted using 35 μl of 95/5 acetonitrile/H2O twice. The sample extracts were diluted with 40 μl of methyl ammonium acetate (1 mM, pH 4.5). Chromatography was performed on a Phenomenex Synergi Max-RP column (2.0 mm × 50 mm, 4 μm). A PE Sciex API 3000 tandem mass spectrometer interfaced with a turbo ionspray source was used for mass detection. Compared to solid-phase extraction, liquid-liquid extraction and solid-supported liquid-liquid extraction methods that were developed and previously used in our laboratory, this method reduced the labor cost and was less time consuming in sample preparation, due to the fact that post-extraction solvent evaporation and reconstitution steps were avoided using this μElution solid-phase extraction plate. The method has been proved to be fast, reliable and reproducible.