A rapid and sensitive assay based on high performance liquid chromatography-tandem mass spectrometry（LC-MS/MS） was developed for the determination of ranitidine（RAN） in human plasma with codeine as internal standard（IS）.After protein precipitation with acetonitrile,the analyte and IS were separated on a Zorbax SB-Aq C18 column（150 mm×4.6 mm i.d.,5 μm） eluted with a mobile phase consisting of methanol/acetonitrile/10 mmol/L ammonium acetate containing 1% formic acid（pH=2.4）（volume ratio 12.5：12.5：75） at a flow rate of 1.0 mL/min.Detection was performed by electrospray ionization in the positive ion mode followed by the multiple reaction monito-ring（MRM） of the transitions of RAN at m/z 315.1→176.3 and of IS at m/z 300.1→165.1.The method was linear over a concentration range of 1―1000 ng/mL（r=0.9991） with a lower limit of quantitation（LLOQ） of 1 ng/mL and a limit of detection（LOD） of 0.3 ng/mL.Accuracy as relative error was from-0.01% to-1.7% and intra-day and inter-day precisions as relative standard deviation were ≤8.9% and ≤5.5%,respectively.The method was successfully applied to a pharmacokinetic study of ranitidine,getting a single oral dose（160 mg） to healthy volunteers.
ZHANG ChaoWANG LuGUAN XinJ. Paul FawcettZHAO Li-meiSUN Yan-tongGU Jing-kai
