An HPTLC Method for the Determination of Minocycline in Human Plasma, Saliva, and Gingival Fluid after Single Step Liquid Extraction

Abstract

A rapid, sensitive and specific high-performance thin-layer chromatographic (HPTLC) method was developed and validated for determination of minocycline in human plasma, saliva, and gingival fluid samples. Densitometric analysis of minocycline was carried out at 345 nm after single step extraction with methanol. The method uses TLC aluminium plates pre-coated with silica gel 60F-254 as a stationary phase and methanol-acetonitrile-isopropyl alcohol-water (5:4:0.5:0.5, v/v/v/v) as mobile phase. In all the three matrices, the calibration curve was linear (r(2) >/= 0.9958) in the tested range of 100 - 1200 ng spot(-1) with a limit of quantification of 15.4 ng spot(-1). Drug recovery from plasma, saliva and gingival fluid averaged 97.7%. Intra- and inter-day accuracies, determined at three different concentrations, were 95.08 to 100.6% and the corresponding precision (% CV) values were < 4.61%. In all the three matrices, rapid degradation of drug occurred and the half-life of drug ranged from 9.9 to 16.1 h at 4 degrees C and from 6.3 to 11.5 h at 20 degrees C. Frozen at -20 degrees C, this drug was stable for at least 2 months and can tolerate two freeze-thaw cycles without losses higher than 10%. The method's ability to quantify minocycline with precision, accuracy and sensitivity makes it useful in pharmacokinetic studies.