Development and validation of an HPTLC method for determination of minocycline in human plasma

A new high-performance thin-layer chromatographic (HPTLC) method has been established for determination of minocycline in human plasma. Chromatography was performed on aluminium plates coated with silica gel 60F(254); the mobile phase was methanol-acetonitrile-isopropanol-water 5:4:0.5:0.5 (v/v). Densitometric analysis was performed at 345 nm. The method is rapid (single-step extraction with methanol), sensitive (limit of quantification 15.4 ng per zone), precise (CV <= 4.61 %), accurate (drug recovery 95.08-100.6%), and linear over the range 100-1200 ng per zone. Recovery of minocycline from plasma samples was 95.8 +/- 4.5%. The half-life of minocycline in plasma was 9.9 h at 4C and 6.3 h at 20C. Minocycline is stable in human plasma for at least two months at -20C and can tolerate two freeze-thaw cycles with losses <10%. The method was successfully used to determine therapeutic levels of minocycline.