ENVIRONMENTALLY FRIENDLY LC/MS DETERMINATION OF EPLERENONE IN HUMAN PLASMA.

Eplerenone (EPL), a selective aldosterone receptor antagonist, is indicated in the treatment of chronic heart failure and hypertension. It is hard to find a green assay among a few published methods for its determination in human plasma or serum. Following a liquid-liquid extraction with methyl t-butyl ether, eplerenone and isotope labelled eplerenone - used as an internal standard - were separated from the endogenous compounds on an Atlantis dCl8 column (150 x 3 mm, 3.0 [im). An isocratic elution with the mobile phase consisting of methanol and ammonium acetate (3 : 2, v/v) was used. A single quadrupole mass spectrometer was operated in positive electrospray ionization using the selected ion monitoring mode. The method is more environmentally-friendly than the previously reported assays. Acetonitrile in the mobile phase was replaced with methanol which is a removable solvent. Plasma sample volume was reduced to 250 pL which significantly decreased waste volume. Chlorinated solvents used previously for liquid-liquid extraction were eliminated and the safety of the laboratory staff was increased by eliminating diethyl ether. The method is characterized by a short analysis time, simple sample preparation and reduction of waste volume, which are important advantages when analyzing large numbers of samples. The method was validated according to international regulatory guidelines and may be applied to human pharmacokinetic studies following a single 25 or 50 mg oral dose.