On-line microdialysis coupled with microbore liquid chromatography for the determination of unbound chloramphenicol and its glucuronide in rat blood.

On-line microdialysis coupled with microbore liquid chromatography was used to investigate the pharmacokinetics of chloramphenicol and its glucuronide in rat blood. A microdialysis probe was inserted into a jugular vein of male Sprague-Dawley rats. Chloramphenicol succinate (20 mg/kg, intravenously) was then administered via a femoral vein. Dialysates were automatically injected onto a LC system, via an on-line injector. Samples were eluted with a mobile phase containing acetonitrile-10 mM monochloroacetic acid (30:70, v/v, pH 3.0). The UV detector wavelength was set at 278 nm. The limit of quantitation for chloramphenicol was 10 ng/ml. The in vitro recoveries of chloramphenicol and chloramphenicol glucuronide at 500 ng/ml were 32.2+/-0.3% and 11.4+/-0.7%, respectively (n = 6). Intra- and inter-assay accuracy and precision of the analyses were < or =10% in the range of 0.01 to 5.0 microg/ml.