Abstract
A rapid, sensitive and selective liquid chromatographyโtandem spectrometry method was developed and validated for determination of paeoniflorin in rat plasma using geniposide as the internal standard. The samples were pretreated with solidโphase extraction using ExtractโCleanโข cartridges. Separation of paeoniflorin and IS was achieved on a reversedโphase C~18~ column (50 ร 4.6 mm i.d.) with a mobile phase made up of acetonitrile and 0.05% formic acid (25:75, v/v) at a flow rate of 0.5 mL/min. Detection was carried out on a triple quadrupole tandem mass spectrometer by multipleโreaction monitoring and an electrospray ionization source was employed as the ionization source. The lower limit of quantification obtained was 4 ng/mL (n = 6) using 200 ยตL plasma with an accuracy of โ3.67% (relative error) and a precision of 4.13% (relative standard deviation). A good linearity was found in the range of 4โ1000 ng/mL. The intraโ and interโday relative standard deviations in the measurement of quality control samples 10, 150 and 800 ng/mL ranged from 3.73 to 4.94% and from 4.31 to 6.56%, respectively. The accuracy was from โ3.93 to โ1.11% in terms of relative error. The analyte and IS were stable in the battery of stability studies. This method was successfully applied to a pharmacokinetic study of paeoniflorin after a single oral administration of 53.36 mg/kg paeoniflorin to rats. Copyright ยฉ 2005 John Wiley & Sons, Ltd.