High-performance liquid chromatography-mass spectrometric analysis of furosemide in plasma and its use in pharmacokinetic studies

This study presents a rapid, specific and sensitive high-performance liquid chromatography-mass spectrometric (LC-MS) assay for the determination of f urosemide in human plasma using diclofenac as an internal standard (IS). Bo th compounds were extracted from human plasma with ethyl acetate at pH 1 an d were chromatographed using Shim-Pack GLC-CN column and a mobile phase con sisting of acetonitrile and 20 mM ammonium acetate buffer solution pH 7, 4: 1 (v/v) at a flow rate 1 ml min(-1). Furosemide and IS were detected by mas s spectrometer operated in the negative single ion monitoring mode using AP CI as an ionization process at m/z 329.2 and 294.1, respectively. The assay linearity of furosemide was confirmed over the range 50-2000 ng ml(-1). De tection limit for furosemide in plasma was 10 ng ml(-1). The selected conce ntration range corresponds well with the plasma concentrations of furosemid e for pharmacokinetic study. Intraday and interday relative standard deviat ions were 1.3-4.7 and 2.7-11.5%, respectively. The extraction recovery perc entages of furosemide and IS from plasma were in the range 89.3-97.1%. The developed LC-MS procedure was applied for the determination of the pharmaco kinetic parameters of furosemide after an oral administration of tablet for mulation (40 mg) to two healthy male volunteers. The calculated parameters were in good agreement with the reported values. (C) 2000 Elsevier Science S.A. All rights reserved.