A very precise high-performance liquid chromatographic procedure for the determination of cefmenoxime, a new cephalosporin antibiotic, in plasma.

A simple and very precise high-performance liquid chromatographic procedure has been developed for the determination of cefmenoxime, a new broad spectrum cephalosporin antibiotic, in plasma. The workup procedure involves ultrafiltration of samples which have been treated with sodium dodecyl sulfate to displace the drug from its binding sites on plasma proteins. The ultrafiltrates are then directly injected into a high-performance liquid chromatographic system utilizing a reversed-phase analytical column, and an ultraviolet spectrophotometric detector. The mean assay coefficient of variation over a concentration range of 0.5-200 micrograms/ml is slightly greater than 1% when either p-nitrobenzoic or p-anisic acid is used as the internal standard. Recoveries of drug are essentially quantitative at all levels investigated; hence the calibration curves are rectilinear from the limit of quantification (about 0.05 microgram/ml) to at least 200 micrograms/ml.