High-performance liquid chromatographic measurement of 8-methoxypsoralen in plasma

Summary A simple high-performance liquid chromatographic method for the measurement of 8-Methoxypsoralen (8-MOP) in human plasma following a single 40mg dose has been described. After addition of phosphate-NaOH buffer, pH 12, and internal standard (trimethylpsoralen), the sample is vortex-mixed with diisopropylether. The resulting extract is analysed on a reverse phase column using phosphoric acid (0.05% v/v): acetonitrile (1:1) as mobile phase, and U.V. detection at 220nm. No interference from endogenous sources has been observed. The limit of sensitivity of the assay is 5ng/ml plasma. The measuring range is between 10–700ng 8-MOP/ml plasma, to be expected from oral doses of 0.6mg 8-MOP/kg body weight, and corresponds to the therapeutic plasma concentration. The relative standard deviation at 50ng/ml level of 8-MOP is 3.6%.