Determination of linezolid in growth media by high-performance liquid chromatography with on-line extraction

An isocratic high-performance liquid chromatography (HPLC) method with on-line extraction has been developed to determine linezolid in Mueller-Hinton broth. The loading mobile phase consisting of water–acetonitrile 99:1 (v/v) allowed retention of the analyte on a LiChrocart 4-4 pre-column filled with a LiChrospher 100 RP-8, 5 μm. The transfer of the analyte by a backflush mode to a 150 mm × 4.6 mm I.D. Kromasil C8 5 μm column was performed using a mobile phase of water–acetonitrile 80:20 (v/v). UV detection at 254 nm allowed a quantification limit of 0.39 μg/mL with a 50-μL sample size. The method was successfully applied to in vitro pharmacokinetic–pharmacodynamic studies.