A sensitive LC-ESI-MS method for the determination of indapamide in human plasma: Method and clinical applications

A sensitive LC-ESI-MS method for the determination of indapamide in human plasma using glibenclamide as the internal standard (IS) was established. Following acidification with 1 M hydrochloric acid solution, plasma samples were extracted with ethyl acetate and separated on a C18 column with a mobile phase of 10 mM ammonium acetate-methanol (22:78, v/v). Indapamide was determined using electrospray ionization in a single quadrupole mass spectrometer. LC-ESI-MS was performed in the selected ion monitoring (SIM) mode using target ions at m/z 364.3 for indapamide and m/z 492.4 for the IS. Calibration curves were linear over the ranges of 0.1-100 ng/ml for indapamide. The lower limit of quantification was 0.1 ng/ml. The intra- and inter-assay precisions were less than 9.5% and 10.6%, respectively. The mean plasma extraction recovery of indapamide was 90.5-93.9%. The method has been successfully applied to study the pharmacokinetics of indapamide in healthy male Chinese volunteers.