Liquid chromatography/electrospray ionization mass spectrometry method for the determination of the active metabolite M‐1 of suplatast tosilate in human plasma

A liquid chromatography/electrospray ionization mass spectrometry (LC/ESIMS) method for the determination of 4‐(3‐ethoxy‐2‐hydroxypropoxy) acrylanilide (M‐1), the active metabolite of suplatast tosilate, in human plasma was established. Plasma samples were extracted with diethyl ether, separated on a C 18 column with a mobile phase of acetonitrile–10 mm ammonium acetate solution containing 0.1% formic acid (28:72, v/v) and detected by ESIMS. The method was linear over the concentration range 0.15–60.0 ng/mL. The lowest limit of quantification was 0.15 ng/mL. The intra‐ and inter‐run relative standard deviations obtained from three validation runs were all less than 8.6%, and the intra‐ and inter‐run relative errors were all less than 3.1%. The method was successfully applied for the evaluation of pharmacokinetic profiles of M‐1 in healthy volunteers. Copyright © 2007 John Wiley & Sons, Ltd.