Liquid chromatography tandem mass spectrometry for the determination of lithospermic acid B in rat serum

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the determination of lithospermic acid B (LSB) in rat serum was developed. LSB and internal standard, 7-hydroxy-3-phenyl-chromen-4-one (HPC) were extracted from rat serum with methyl-tert-butyl ether at acidic pH and analyzed on a Luna C-8 column with the mobile phase of acetonitrile-ammonium formate (10 mM, pH 6.5) (50:50, v/v). The analytes were detected using a negative electrospray ionization tandem mass spectrometry in the multiple-reaction-monitoring mode. The standard curve was linear (r(2) = 0.997) over the concentration range of 10.0-500 ng/mL. The coefficient of variation and relative error for intra- and inter-assay at three QC levels were 1.1similar to6.2% and -10.3similar to-2.7%, respectively. The recovery of LSB from serum sample ranged from 73.2 to 79.5%, with that of HPC (internal standard) being 75.1%. The lower limit of quantification for LSB was 10 ng/mL using 50 muL of serum sample.