HIGH-THROUGHPUT DETERMINATION OF LINEZOLID IN HUMAN PLASMA BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

A simple, high-throughput reversed-phase high performance liquid chromatography method with mass spectrometric detection (LC/MS/MS) was developed and validated for the quantification of linezolid in human plasma. After preparation, the sample was analyzed by isocratic elution on a Kinetex-C18 (50 × 2.1 mm, 2.6 µm) column. The mobile phase consisted of a mixture of acetonitrile: water containing 1 mM ammonium formate (25:75 V/V). Detection was performed in the multiple reaction monitoring (MRM) mode, using an electrospray ion source, positive ionization; the ion transition was monitored in the m/z 338.0 → m/z 296.2 range. Calibration was performed in the 0.256 to 20.130 µg/mL concentration range by using a quadratic least-squares regression, with a R2 higher than 0.995. The determined LOQ of linezolid in plasma was 0.256 µg/mL, the intra-day recoveries were in the 98.0 ± 4.5%–104.8 ± 4.5% range and the precision, for n = 5, was 4.5 to 8.6%. No interference was observed at the retention time (tR = 0.75 min)...