Liquid chromatography/tandem mass spectrometry for the determination of magnesium lithospermate B in beagle dog serum

A sensitive and specific isocratic liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the quantification of magnesium lithospermate B (MLB) in beagle dog serum with silibinin as internal standard. The serum samples were treated by special liquid-liquid extraction, and the analytes were determined using electrospray negative ionization mass spectrometry in the selective monitoring mode, with sufficient sensitivity to allow analysis of dog serum samples generated following administration of a clinically relevant dose. The calibration curve for MLB was linear over the range 8-2048 ng/ml with coefficients of correlation >0.999. The intra- and inter-day precisions (CV) of analysis were <7%, and accuracy ranged from 90 to 106%. This quantitation method was successfully applied to a pharmacokinetic study of i.h. administration of MLB with dosages of 3, 6, 12 mg/kg in beagle dogs.