Development and validation of a liquid chromatography–tandem mass spectrometry method for the determination of xanthinol in human plasma and its application in a bioequivalence study of xanthinol nicotinate tablets

A sensitive, rapid liquid chromatographic–electrospray ionization mass spectrometric method for the determination of xanthinol in human plasma was developed and validated. Xanthinol nicotinate in plasma (0.5 mL) was pretreated with 20% trichloroacetic acid for protein precipitation. The samples were separated using a Lichrospher silica (5 μm, 250 mm × 4.6 mm i.d.). A mobile phase of methanol–water containing 0.1% formic acid (50: 50, v/v) was used isocratically eluting at a flow rate of 1 mL/min. Xanthinol and its internal standard (IS), acyclovir, were measured by electrospray ion source in positive selected reaction monitoring mode. The method demonstrated that good linearity ranged from 10.27 to 1642.8 ng/mL with r = 0.9956. The limit of quantification for xanthinol in plasma was 10.27 ng/mL with good accuracy and precision. The mean plasma extraction recovery of xanthinol was in the range of 90.9–100.2%. The intra- and inter-batch variability values were less than 4.8% and 7.9% (relative standard deviation, R.S.D.), respectively. The established method has been successfully applied to a bioequivalence study of two xanthinol nicotinate tablets for 20 healthy volunteers.