Abstract:  The formononetin in the Millettla nitida Benth. var. hirsutissima. Z.Wei was analyzed by HPLC-Mass spectrometry. By means of acetonitrile-0.1% formic acid as mobile phase with flowing rate at 0.8ml/min,exploiting Spherisord ODS(250mm ×4mm,5μm)with gradient elution,the tandem mass spectral acquisition was done in positive and negative electrospray ionization. The result showed that the plant studied here contained formononetin.The linear range of this method was from 6.0 to 126.0μg/ml. The limit of detection(LOD,S/N=3) and limit of quantity(LOQ,S/N=10) were 0.8μg/ml and 2.7μg/ml respectively. The recoveries were between 99.6%～104.3%. The method can be applied for the determination of formononetin in the Millettla nitida Benth. var. hirsutissima. Z.Wei because of its briefness,rapidity,good sensitivity and recovery.

Key words:  , HPLC-MS； Millettla nitida Benth. var. hirsutissima. Z.Wei； formononetin；