A sensitive and reliable LC-ESI-MS method for simultaneous determination of nine ginsenosides (Rh(1), Rg(2), Rg(1), Rf, Re, Rd, Rc, Rb(2) and Rb(1)) in rat plasma was developed and validated using saikosaponin A as an internal standard. The samples were extracted by solid-phase extraction. Chromatographic separation was carried out on a Hypersil Gold C(18) column (100 × 2.1 mm, 5 µm) by stepwise gradient elution with water (0.1% formic acid, v/v) and acetonitrile as the mobile phase. Detection was determined by selective ion monitoring mode using electrospray ionization in the negative ion mode. Good linearity over the investigated concentration ranges was observed with the values of r higher than 0.9900. The intra- and inter-day precisions were all no more than 15% and the average recoveries varied from 71.8 to 91.7%. This quantitative measurement was successfully applied to a pharmacokinetic study of Yi-Qi-Fu-Mai injection.
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