A rapid, direct, accurate and sensitive liquid chromatographic assay with on-line extraction for minocycline of nude mice serum is described. Serum was directly injected onto the extraction column where the drug was separated from the serum concomitants using a solid phase extraction procedure based on cation exchange. Using an on-line column switching system, minocycline was quantitatively transferred and separated on the analytical column. Ultraviolet absorption at 352 nm was used for detection. The assay was linear from 0.2 to 10 mu g/mL with a correlation coefficient of 0.999. Detection limit was 50 ng/mL. Recovery was 97%. The method has been developed for the determination of minocycline levels of nude mice serum collected from a study designed to evaluate the potential for tumor anti-angiogenic effects of this drug.
