Abstract: An analysis method was established to determine four kinds of furocoumarines (isopsoralen,psoralen,5-methoxy-psoralen and imperatorin) in citrus essential oil by ultra-high performance liquid chromatography (UPLC) with a diode array detector (DAD).The essential oil sample was diluted with methanol.After centrifugal separation,the supernatant was directly analyzed by UPLC.The separation was performed on an Agilent Zorbax Eclipse Plus C₁₈ column (2.1 mm×50 mm,1.8 μm),with water-acetonitrile as the mobile phase in gradient elution mode at a flow rate of 0.3 mL·min^-1.The detection wavelength was 300 nm.The results indicated that good linearity is obtained in the mass concentration range of 0.5-100 mg·L^-1 with all correlation coefficients of 0.999 for the four kinds of furocoumarines.The detection limits are 1.5-3.0 mg·kg^-1 .The recoveries at three spiked levels of four kinds of furocoumarines are ranged within 97.5%-105.6%,with the relative standard deviations of 0.4%-2.9% (n=3).Furthermore,25 batches of citrus essential oil samples were determined using the established method and a batch of grapefruit oil was found containing 60.5 mg·kg^-1 of 5-methoxy-psoralen.

Key words: citrus essential oil, ultra-high performance liquid chromatography, isopsoralen, psoralen, 5-methoxy-psoralen, imperatorin