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 60F254; 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 halflife of minocycline in plasma was 9.9 h at 4°C and 6.3 h at 20°C. Minocycline is stable in human plasma for at least two months at -20°C and can tolerate two freeze–thaw cycles with losses <10%. The method was successfully used to determine therapeutic levels of minocycline.