Simple, sensitive, and rapid LC-MS method for the quantitation of indapamide in human plasma - Application to pharmacokinetic studies

A sensitive and specific liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) method was developed and validated for the identification and quantification of indapamide in human plasma. After the addition of the internal standard (IS) and 0.1 M sodium hydroxide solution, plasma samples were extracted with diethyl ether. The organic layer was evaporated under a stream of nitrogen at 40°C. The residue was reconstituted with 200 μL methanol. The compounds were separated on a stainless-steel column (C 18 Shim-pack 5 μm 150 mm×2.0 mm I.D., Shimadzu) at a flow rate of 0.2 mL/min by a gradient elution. Detection was performed on a single quadrupole mass spectrometer by selected ion monitoring (SIM) mode via an electrospray ionization (ESI) source. The method was proved to be sensitive and specific by testing six different plasma batches. Linearity was established for the range of concentrations 0.5-100.0 ng/mL with a coefficient of determination ( r ) of 0.9998 and good back-calculated accuracy and precision. The intra- and inter-day precision (RSD%) was lower than 10% and accuracy ranged from 85% to 115%. The lower limit of quantification was identifiable and reproducible at 0.2 ng/mL with 0.2 mL plasma. The proposed method enables the unambiguous identification and quantification of indapamide for pharmacokinetic, bioavailability, or bioequivalence studies.