Method development for determining the antibacterial linezolid in human serum by micellar electrokinetic capillary chromatography.

A precise method for determining linezolid concentration in human serum by micellar electrokinetic capillary chromatography has been developed and validated. Serum was deproteinized with acetonitrile and etofylline was used as an internal standard. A borate buffer (pH 10.0; 25 mM) containing sodium dodecyl sulfate (80 mM) was used as a running buffer. Detection was performed at UV253 nm by applying 25 kV voltage to a fused-silica capillary tube. Migration time of linezolid was approximately 14 min. Good linearity (0-100 mg/l) was obtained and the limit of detection was 0.5 mg/l (S/N=3). This technique covered the clinical concentration (4 mg/l) measurement of this drug enough. The intra- and inter-day reproducibility was good. Serum recovery was 95-102%. No interference from other anti-microbial agents was observed. Linezolid after serum deproteinization showed high stability. This method was easy to operate as well as economical as a method for determining linezolid in serum.