Rapid and sensitive determination of the antibiotic linezolid in low plasma volumes by high-performance liquid chromatography.

A rapid and sensitive method for the determination of linezolid by high-performance liquid chromatography (HPLC) with UV detection (251 nm) is presented. Linezolid is an important antibiotic against severe infections caused by multi-resistant bacterial pathogens. Scientific efforts continue investigating its effectiveness in different conditions and patient populations including children and newborns. Because plasma samples in a pediatric setting or from animal models are usually collected in low volumes, there is a necessity for a reliable and precise analytical method that is reliable and precise even at sample volumes below 50 microL. The presented method is suitable for plasma sample volumes of 20 microL and can be performed with basic HPLC equipment. Linezolid is extracted from plasma with 10% methanol-90% dichloromethane at neutral conditions and separated isocratically on a microbore ODS column using ammonium acetate buffer (pH 4.4, 0.5%, w/v) and acetonitrile (84:16, v/v) as the eluent. The method exerts linearity from 0.05-40 mg/L and meets commonly accepted specifications regarding accuracy and precision.