determination of repaglinide in human plasma by high-performance liquid chromatography–tandem mass spectrometry

A rapid and sensitive method based on high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been developed for the determination of repaglinide in human plasma. The analyte and internal standard (I.S.), diazepam, were extracted from plasma (25 μL) by liquid–liquid extraction with diethyl ether–dichloromethane (60:40, v/v) and separated on a XDB-C18 column using acetonitrile–ammonium acetate buffer (pH 6.8, 0.01 mol/L) as mobile phase. The retention times of repaglinide and I.S. were 1.95 and 2.35 min, respectively. Detection was carried out using API 4000 mass spectrometer with an ESI interface operating in the multiple reaction monitoring (MRM) mode. The assay was linear over the concentration range 0.050–50 ng/mL with a limit of detection (LOD) of 0.010 ng/mL. Intra- and inter-day precisions (as relative standard deviation, R.S.D.) were ≤5.07% and ≤11.2%, respectively, and accuracy (as relative error, R.E.) was from −0.593% to −1.26%. The assay was successfully applied to a pharmacokinetic study involving a single oral administration of a tablet containing 2 mg repaglinide to each of 10 healthy volunteers.