Liquid chromatography‐tandem mass spectrometry for the determination of a new oxazolidinone antibiotic DA‐7867 in human plasma

A liquid chromatography‐tandem mass spectrometric (LC/MS/MS) method for the determination of a new ox‐azolidinone antibiotic DA‐7867, ( S )‐[ N ‐3‐(4‐(2‐(1‐methyl‐5‐tetrazolyl)‐pyridine‐5‐yl)‐3‐uorophenyl)‐2‐oxo‐5‐oxazolidinyl]methyl acetamide, in human plasma was developed. DA‐7867 and internal standard, linezolid, were extracted from human plasma with ethyl acetate at acidic pH. A reverse‐phase LC separation was performed on Luna C 8 column with the mixture of acetonitrile–ammonium formate (10 m m , pH 4.5; 35:65, v/v) as mobile phase. The analytes were determined using an electrospray ionization tandem mass spectrometry in the multiple‐reaction‐monitoring mode. The lower limits of quantication for DA‐7867 was 2.5 ng/mL. The single liquid–liquid extraction quantitatively recovered DA‐7867 and internal standard from plasma samples at the ranges of 82.2–86.7%. DA‐7867 was stable in blank human plasma at room temperature for 24 h and following three freeze–thaw cycles. Copyright © 2003 John Wiley & Sons, Ltd.